Purification of Zirconium Tetrachloride from UNF Cladding Reports/FY 2015/15... · 2019-01-03 ·...

Purification of Zirconium Tetrachloride from UNF Cladding

Fuel Cycle Research and DevelopmentCraig Barnes

University of Tennessee, Knoxville

Kimberly Gray, Federal POCJulia Tripp, Technical POC

Project No. 15-8323

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Final Report for NEUP DOE project 15-8323

Milestone ID: M2NU-15-TN-UTK_0203-011 Rigor Level: QRL4 Milestone Title: Final Report Prepared and Submitted by: Craig Barnes Submitted to: DOE-NEUP; Julia Tripp TPOC Date: December 19, 2018

Final Report Abstract

The overarching objective of this project was to design and demonstrate (laboratory scale) a sublimation-based purification protocol to obtain pure zirconium chloride (ZrCl4) from impure feeds derived from the direct chlorination of Zircaloy cladding materials. To achieve this objective the following goals were identified.

1. Design, construct and test an apparatus capable of subliming and purifying ZrCl4 at room pressure and temperatures between 600 and 700K (sublimation point of ZrCl4 606 K).

2. Investigate reactions that may be used to chemically alter the makeup of the impure ZrCl4 feed materials to enhance their removal from ZrCl4 in the sublimation-purification process.

3. Computationally model the reactions of metal chlorides in the gas phase under sublimation conditions (1 atm, 600 K) to determine if oligomers are formed and, if formed, how they would influence sublimation-based purification strategies.

All experimental investigations performed as part of this project used stable (non-radioactive) compounds and materials as surrogates for the impure ZrCl4 feedstocks that would be derived from the direct chlorination of Zircaloy claddings from spent nuclear fuel rods. No radiologically active materials were used at any time in this project. The impure ZrCl4 feedstocks used in this study were derived from the direct chlorination of virgin Zircaloy claddings (Zirc-2, -4 and high Nb).

The main goals of the project have been achieved during the three year period of this NEUP sponsored project. The impurities of greatest concern in the feedstocks were identified as the chloride salts of the alloying metals originally found in Zircaloy (Fe, Nb) and radiological contaminants (Cs, Sr, and Sb). A series of prototype sublimation apparatuses and heating arrange-ments were designed, constructed and tested. A general batch-sublimator design was identified and a 1.0 kg batch sublimator/oven system was fabricated from glass. Purification protocols developed on small scale runs were found to scale to 1.0 kg batches without problem.

Purification factor ranges (PFs: wt% final / wt% initial) for the impurity chlorides identified above have been measured: Fe (40 – 500); Nb (10 – 70); Cs (520 – 5000); Sr (250 – 1900); Sb (220 – 2300). Removal of iron is sensitive to the partial pressure of hydrogen (in nitrogen) flowing through the system. Lower PFs are obtained when the hydrogen partial pressure is lower. Lower flows are required to raise the iron PF. Removal of niobium is very sensitive to the endpoint determination of the forerun. When judged properly (color change yellow to white in sublimate) reasonable PFs (500) can be achieved. However, as discussed in the conclusions section, endpoint determination can be difficult and significantly lower PFs may be obtained when the endpoint is not correctly identified. Several methods of obtaining quantitative cesium, strontium and antimony PFs were investigated, the best being ICP-MS. The results reported here reflect very limited access to and ICP-MS instrument during the course of this project. It should be noted that,

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while significantly reduced amounts of antimony are observed in the product, antimony is also found in the exhaust trap after the condenser.

Quantum chemical computational modeling studies of the reactions of metal chlorides in the gas phase provided important information about a chemical transport mechanism that could defeat sublimation-based purification strategies. Many metal chlorides are known to oligomerize in the gas phase to reduce their coordinative unsaturation. Dimerization of ZrCl4 with iron or niobium chlorides would provide a mechanism by which both metal impurities could be carried over with the product during sublimation of the bulk material. Computational modeling conclusively showed that under sublimation conditions in the gas phase, dimerization reactions are not favored thermodynamically due to a significant entropic penalty for the reaction. Therefore, consistent with experimental observations, sublimation-based purification strategies remain viable.

The experimental part of the report concludes with a short discussion of the issues that still remain in developing a technologically relevant Zircaloy recycling strategy.

The final section of the report is a summary of the quantum chemical investigation of the reactions of metal chlorides in the gas phase under sublimation conditions.

Table of Contents

Final Report Abstract ...................................................................................................................... 1

Background: Defining the problem ............................................................................................... 3

Sublimation-based Purification Strategies ...................................................................................... 3

Chemical modification of iron and niobium chloride salts to enhance their separation from zirconium chloride .......................................................................................................................... 4

Description of Protocol ................................................................................................................... 6

Description of Zirconium Chloride Samples used in Purification Studies ..................................... 6

Scale-up study results ................................................................................................................... 11

Conclusions and Prospects for a Technologically Relevant Recycling Strategy ......................... 12

A Quantum Chemistry Modeling Study of the Gas Phase Reactions of ZrCl4 and Metal Chlorides ....................................................................................................................................... 17

Gas Phase Reactions of zirconium chloride and metal chlorides derived from Zircaloy direct chlorination reactions ................................................................................................................ 18

Results ....................................................................................................................................... 23

References ..................................................................................................................................... 38

Supplemental Tables and Figures of Quantum Chemical Models of Metal Chloride Species Investigated in this Project ............................................................................................................ 41

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Background: Defining the problem

In the direct chlorination of used Zircaloy cladding materials, it has been reported that the alloying metals (Sn, Nb, Fe, Cr, Ni) present as alloying metals in claddings are also chlorinated and contaminate the final ZrCl4 product.[2] Table 1 summarizes the nominal concentrations of these metals in several alloys currently used nuclear reactors. Most of the alloying metals shown in Table 1 have been detected in the ZrCl4 product presumably as their chloride or oxychloride salts.

Table 1 Nominal composition of Zircaloys commonly used in nuclear fuel rods (wt%)

Element Zircaloy-2 Zircaloy-4 High Nb-Zircaloy

Sn 1.4 1.3 0.95

Nb <0.01 <0.01 1.1

Fe 0.18 0.21 0.04

Cr 0.1 0.12 <0.01

Ni 0.07 <0.01 <0.01

O 0.12 0.12 0.12 Other trace impurities present: Al, C, Co, Cu, Hf, Mg, Mn, Mo, Si, W, Ti, Sb. Radiological contaminants: 241Am, 244Cm, 137Cs, 60Co, 154Eu, 125Sb, 90Sr

In addition to the alloying components, used cladding is also contaminated with several radio-logical impurities from the fission reactions. This contamination causes it to be classified as high-level waste. The exact profile of contaminant isotopes present in used cladding will vary considerably depending on a number of factors such as fuel history, cooling time, and pretreatment. Activity measurements indicate that radioactive isotopes are present in trace amounts (ppm range) but this will also be a function of use history and pretreatment protocols before purification procedures commence. Regardless of source or history, direct chlorination reactions generally yield products that are both impure (with alloying metals) and contaminated with radiologically active species. Important radiological contaminants investigated in this study using stable isotope surrogates are cesium, strontium and antimony.

Sublimation-based Purification Strategies

Using the sublimation behavior of ZrCl4 as a point of reference, metal chloride contaminants may be divided into three groups based on their vapor pressures (Figure 1). First, NbCl5 and several other high valent metal chlorides (e.g. SbCl5) have low boiling or sublimation points and remain as molecular species in both condensed and vapor phases. They exhibit volatilities similar to or higher than ZrCl4 and could be contaminants in the product from the direct chlorination. Second, lower valent chlorides (e.g. FeCl2, CrCl2, etc.) generally form nonvolatile coordination polymers in the solid state with high sublimation temperatures and are not expected to contaminate the ZrCl4 sublimate. Actinide chloride salts fall into this category. Finally, two well-known metal chloride species exhibit vapor pressures that are quite similar to ZrCl4, namely niobium oxychloride (NbOCl3) and ferric chloride (FeCl3). Significant contamination of the Zircaloy chlorination pro-duct has been observed for both species.

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Chemical modification of iron and niobium chloride salts to enhance their separation from zirconium chloride

Niobium oxychloride and ferric chloride are two of the more challenging contaminants that must be removed from ZrCl4 feeds. As shown in Figure 1, their volatilities is very similar to that of ZrCl4 throughout the sublimation temperature range.

A second, related issue confronting purification schemes is the potential loss of zirconium due to incidental exposure to water (e.g. humid air) and partial hydrolysis during handling. Polymeric oxychlorides of zirconium are usually not volatile and would be lost in sublimation-based protocols, thus lowering the yield of the desired product.

A strategy to address both of these challenges is to chemically transform (deoxygenate) niobium oxychloride and partially hydrolyzed zirconium oxy chlorides into pure chlorides before the bulk sublimation process is started. Once the niobium in the system is transformed into the penta-chloride, the high volatility of NbCl5 relative to ZrCl4 may be used to find conditions where NbCl5 can be selectively sublimed from the system while minimizing the loss of ZrCl4. This is the strategy that is used to separate niobium from zirconium in the purification protocol described below.

A reagent that is known to cleanly deoxygenate many metal oxides and oxychloride complexes is thionyl chloride (SOCl2).[3] In the case of niobium, NbOCl3 will be transformed into the desired pentachloride and can thus be separated from zirconium in a sublimation forerun.

𝑁𝑏𝑂𝐶𝑙 𝑆𝑂𝐶𝑙 → 𝑁𝑏𝐶𝑙 𝑆𝑂

Thionyl chloride is also used to remove water or hydroxide containing impurities from water sensitive metal complexes and can therefore be used to transform mixed oxide-chloride zirconates into the pure chloride salt (ZrCl4).[4]

Figure 1 Vapor pressure vs. Temperature for ZrCl4 and other chlorides. (Vapor Pressure curves based on data obtained from reference [1].)

0.00001

0.0001

0.001

0.01

0.1

1

10

100

1000

175 225 275 325 375 425

ZrCl4

NbOCl3

NbCl5 FeCl3

Va

po

r p

ress

ure

(atm

)

Temperature (°C)

High volatility: SiCl4, SbCl3, SnCl4

Low volatility: CsCl, CoCl2, CrCl2, CrCl3, NiCl2, FeCl2, SnCl2

sublimation region

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𝑍𝑟𝑂 𝐶𝑙 𝑆𝑂𝐶𝑙 → → 𝑍𝑟𝐶𝑙 𝑆𝑂

𝑍𝑟𝑂𝐻 𝐶𝑙 𝑆𝑂𝐶𝑙 → → 𝑍𝑟𝐶𝑙 𝐻𝐶𝑙 𝑆𝑂

Treatment of chlorination mixtures with thionyl chloride will increase the yield of the desired product (ZrCl4) and transform NbOCl3 to NbCl5. The byproducts of these reactions, HCl and SO2, are easily removed from the system and trapped.

An additional contaminate of concern is ferric chloride (FeCl3). Like NbOCl3, FeCl3 has a volatility very similar to that of ZrCl4 throughout the sublimation temperature range of interest. In contrast to ferric chloride, the ferrous analogue is completely nonvolatile in the temperature-pressure region to be used for purification. Thus reduction of FeCl3 to FeCl2 should be an effective method to separate iron from zirconium chloride in a sublimation protocol.

A well-known reagent that selectively reduces ferric chloride to the ferrous salt is hydrogen gas (H2) at ~250°C.[5] FeCl3 is quantitatively transformed into the FeCl2 with the only byproduct being HCl.

2 𝐹𝑒𝐶𝑙 𝐻 → 2 𝐹𝑒𝐶𝑙 2 𝐻𝐶𝑙

While the conditions for selectively reducing iron with hydrogen gas are well known,[5] the reaction of thionyl chloride with metal oxides has only been described for conditions involving sealed reaction vessels and high pressure.[6] The purification protocol that we seek to develop should function in open, flow systems near room pressure. Therefore, some protocol development is necessary.

North[7] and Hecht[6b] have described the reactions of thionyl chloride with metals and metal oxides at high temperature and pressure (laboratory scale, sealed quartz tubes). Most metals and metal oxides react to form the homoleptic chlorides at temperatures between 100 – 300°C. In these studies the solids (metal powder or oxide) were in contact with liquid SOCl2 so that the chemical potential of thionyl chloride is much higher than can be achieved in gas phase reactions at ~1 atm. A thermodynamic analysis of the reactions of zirconium oxide and niobium oxide indicates that both reactions are favored under sublimation conditions.[8] In the case of the oxide, thionyl chloride acts as both a chlorinating agent and an oxygen “getter” in these reactions, with sulfur dioxide being is the ultimate oxygen-containing product in the system.

Based on the information above, initial protocol conditions investigated for the deoxygenation of niobium and zirconium in the chlorinated products were between 200 and 250°C. This tempera-ture range should be high enough for thionyl chloride to chlorinate and deoxygenate metal species present but low enough to prevent zirconium chloride from moving from the sublimator into the condenser while niobium pentachloride is collected during the forerun. Finally, the vapor pressure of NbCl5 in this temperature range should be high to achieve reasonable throughput in the forerun in an acceptable time frame.

The main protocol variables investigated were temperature, flow and collection time for the forerun. A major concern in this step of the protocol is the determination of the endpoint for the collection of niobium in the forerun. The endpoint was determined visually. NbCl5 is a bright yellow solid while ZrCl4 is colorless (white). Therefore, when the sublimate turned white, the collection of the forerun was considered complete and the sublimation halted so that a new condenser could be attached to the system.

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Description of Protocol

With the above two chemical treatment steps in mind, our overall purification strategy may be divided up into two stages:

Stage 1: Chlorination and removal of niobium from zirconium chloride. Step 1. Rechlorination of oxide/hydroxide zirconates and NbOCl3 via exposure to thionyl

chloride (SOCl2). Step 2. Remove high volatility metal chlorides (primarily NbCl5) via collection of a forerun.

Stage 2: Reduction of iron and collection of pure ZrCl4 Step 3. Reduction of FeCl3 to nonvolatile FeCl2 with hydrogen gas Step 4. Collection of pure ZrCl4 from nonvolatile metal chlorides via bulk sublimation.

Small scale, proof of concept studies for the above protocol are described in milestone reports 07, 08, and 09 for this project. Milestone report 07 describes a new larger scale sublimation system (glass apparatus and box furnace) that was used in the studies described in this report.

The description that follows provide details (times, temperature, flowrates) of the protocol that have been developed based on the above chemical strategies for obtaining pure zirconium tetra-chloride from Zircaloy cladding materials.

Description of Zirconium Chloride Samples used in Purification Studies

ZrCl4 samples derived from chlorination runs of virgin Zircaloy cladding samples were obtained from ORNL and stored in a nitrogen glove box until used. These samples generally represented the products of multiple chlorination reactions with different types of claddings run over several years and mixed together. Therefore, separate elemental analyses (ICP-OES) were performed for each batch used in these studies. None of the samples contained cesium, strontium or antimony as received. These components were added to each batch as the chloride salts (Cs, Sr) or the oxide (Sb2O5) to achieve ~50 ppm concentrations. After addition of Cs, Sr and Sb salts, samples were ground together and mixed thoroughly.

In addition to scaling up batch size, several variations of the experimental protocol were investi-gated with the goal of simplifying the procedure as well as shortening it without compromising yield and purity. The basic steps in the protocol are described in detail below, summarized in Table 2 and illustrated in Figure 2. Note: Descriptions of all parts of the sublimation apparatus and box furnace may be found in Milestone report 07 for this project.

Loading and Sealing the Sublimator 1. The sublimator bottom is positioned in the furnace and connected to the condenser located

outside the furnace wall (see Milestone 07 report for illustrations). A glass “snorkel” is positioned inside the sublimation bottom over the exhaust line to prevent solids from filling and blocking gas flow through the exhaust line. This also forces gas flow in the apparatus to be directed into a vertical column (inside the snorkel) above the exhaust port entrance to prevent gas channeling in large batches that cover the exhaust port and line.

2. A plastic jar is loaded with impure ZrCl4 in the dry box, brought out and quickly poured into the sublimator bottom. The sublimator top with graphite gasket is quickly (to minimize hydrolysis with water vapor) reseated on the glass flange of the bottom and sealed with a

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metal pressure clamp. The system is checked for leaks by means of a bubbler on the exhaust of the condenser vessel.

Basic Sublimation Protocol (see also Table 2 and Figure 2 – 6)

Stage 1: Rechlorination of zirconium and niobium and collection of NbCl5 the forerun 1. Once sealed, the system is purged with dry nitrogen for 30 minutes while heating to 100°C.

Thionyl chloride (SOCl2) is then introduced into the sublimator as a saturated stream in nitrogen via a bubbler. Details of times, temperature profiles and flows for this step are summarized in Table 2.

2. The sublimator is then heated to 200 – 250°C continuing N2/SOCl2 purge until the endpoint of the forerun is reached. Collection of the Nb-rich forerun is then halted and the system is purged with nitrogen gas (Table 2).

3. The sublimator is cooled to RT and the condenser with forerun is separated from the sublimer. The forerun material in the condenser is taken into nitrogen glove box and a new condenser is connected to the system under nitrogen.

Stage 2: Reduction of iron to ferrous state and collection of ZrCl4 product 4. The remaining solid residue in sublimation bottom is heated from RT to either 275 or

400°C. When 100°C is reached, a H2/N2 purge is initiated. H2/N2 mixes investigated in this study are summarized in Table 3.

5. ZrCl4 is then collected at ~350 – 400°C under H2/N2 purge until solid ceases to form in the condenser. Typical collection times varied as described in Table 2.

6. The entire apparatus is cooled to RT and the product taken into dry box in the condenser vessel. The residue in sublimator bottom is collected in air, weighed and analyzed.

It should be noted that the protocol, as developed here, must be halted at the end of Stage 1 and the apparatus cooled to room temperature to replace the forerun condenser with one that will be used to collect the product. As is discussed below, the protocol could be significantly simplified if a high temperature value were to be installed between the sublimer and condenser. With such a valve the two stages of the protocol could be run without halting the process. Further discussion of apparatus/protocol improvements may be found in the summary and conclusions section of this report.

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Figure 2 Illustration of basic purification protocol used in scale-up runs described in this report. Variations in the protocol are summarized in Table 3 and illustrated Figures 3 – 6.

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with SOCl2

Flow Rate (cc/m

in)

Temperature of Rea

ctor (°C)

Removal of NbCl5 in forerun

Cool to RTCondenser exchange

Stage 1 Stage 2

X h

Y hZ h

Time of Reaction (hours) 5.5 11 16.5 22 27.5 33 38.5 44 49.5 55

Collection of ZrCl4

~1 atm ZrCl4 vapor pressure 330°C

Nitrogen

Thionyl Chloride/N2

variable % Hydrogen/N2

Temperature

Flows

Reduction of iron

N h

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Table 2 Basic steps in Sublimation-based Room Pressure Purification Protocol of ZrCl4

*Nitrogen flow through a SOCl2 bubbler: (25°C, 60 cc/min, 3.15 g/hr; (𝑝 ~15.7 kPa (0.154 atm; 117 torr))

Stage 1 Time Temp (C°)

Flow (ccm/min)

Comments

Warm-up 1 h 20 - 200 60 (N2) N2 only, until 100 C then N2 saturated with SOCl2 (uses ~3.2 g

SOCl2/h)

Chlorination 16 h 200 60 (SOCl2/N2)* Small amount of red material seen in collector, considered it forerun

Forerun Collection 4 h 200 - 250 60 (SOCl2/N2)*large volumes of dark red material observed that progressively

lightens in color. Cut off determined when material is white and rate of solid formation in condenser slows

Cooldown 2 h 250 - 20 60 (N2) N2 purge only

Stage 2 Time Temp (C°)

Flow (ccm/min)

Comments

Warm-up 2 h 20 - 275 30 (N2) N2 only, until 100 C then H2/N2

Reduction of FeCl3 16 h 275 30 (H2/N2) Small amount of white material seen in collector, considered product.

Collection of ZrCl4 6 h 275 - 400 60 (H2/N2) 50/50 H2/N2

Cooldown 4 h 400 - 20 60 (N2) H2/N2 turned off once temperature fell to 150

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Table 3 Description of Protocol Variations used in Scale-up Runs 300 g – 1000 g

Run Protocol Variations

Run 1 (300 g)

NbCl5 (~1 wt%), CsCl (~50 ppm), SrCl2, (~50 ppm) and SbCl5 (initially as Sb2O5; ~50 ppm) added to starting material. Slow flows were used in both Nb chlorination and iron reduction steps. 100% H2 used for iron reduction. The antimony oxide, initially added to the mixture, is completely transformed into SbCl5 in the thionyl chloride treatment (Stage 1). The pentachloride is quite volatile and is not found in any part of the sublimation apparatus (residue left in sublimation bottom or cold condenser). Antimony has been found in exhaust traps in previous sublimation runs. (See Figure 3, See appendix)

Run 2 (323 g)

Sample source and composition similar to Run 2 but faster flows used to investigate reducing run times. H2 concentration was 50% in nitrogen for the reduction of iron. A shorter reduction/ZrCl4 time was used . (See Figure 4, See appendix)

Run 3 (500 g)

Sample source and composition similar to Runs 2, 3. H2 concentration reduced to 10 – 5% in nitrogen. The usual collection times were used. (See Figure 5, See appendix)

Run 4 (1000 g)

Sample source and composition similar to Runs 2, 3 and 4. The H2 concentration was varied between 20 – 5% in nitrogen. The usual collection times were used.(See Figure 6, See appendix)

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Table 4 Summary of Scale-up Purification Factors for batch runs between 150 g – 1000 g

Run Sample ZrCl4 Yield (%)

Fe PF

Nb PF

Cs PF / % in residue

Sr PF / % in residue

1 300 g chlorinated Zircaloy

w/ 1.16 %Nb, 54.3 ppm Cs, 53.7 ppm Sr

79.4 560 68 5804 / 104.5

1965 / 6.4


w/ 1.08 %Nb, 45.4 ppm Cs, 47.4 ppm Sr, 50.9 ppm Sb

87.1 134 62 – – / 107.8


w/ 1.25 %Nb, 61.0 ppm Cs, 56.7 ppm Sr, 47.4 ppm Sb

84.8 31* 14

** – – / 90.7

4§ 1000 g chlorinated Zircaloy w/ 1.25 %Nb, 68.0 ppm Cs,

54 ppm Sr, 110 ppm Sb 89.3% 40

10 – 4 **

520 / – 250 / –

*The iron PF is low because a plastic component used in the sublimation condenser failed and contaminated the product.

**The Nb PF low for these runs because the endpoint of the forerun was incorrectly recognized and cut short of complete niobium removal

§Antimony purification factor (220) determined by ICP-MS analysis of the product. Antimony found in the trap on exhaust line

from condenser

Scale-up study results

Run 1 (300 g) Niobium (1 wt%), cesium, strontium and antimony (~50 ppm) were added to the feed. Slow flow rates were used in both stages of the run. The yield of product is someone lower than in most other runs because the endpoint for product collection was incorrectly identified and collection halted early. At the same time, very high PFs were recorded for alloying impurities and radiological surrogates. These results are consistent with our previous observations that the success of the purification strategy developed here is highly dependent on the flow and temperatures used in both stages as well as the endpoint determination both for forerun collection and product collection. Cesium analyses must be performed using ICP-MS. We have limited access to this instrument. Analyses pending.

Run 2 (323 g) The yield of product is now very close to what has been observed in previous runs (~90%). PFs for Fe and Nb remain acceptable even though higher flow rates in both stages of the protocol were used. Higher flow rates were used to shorten the times for each stage.

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Run 3 (500 g) The major change in protocol here was the lower hydrogen concentration (5 – 10%) used in the reduction of iron in Stage 2 of the protocol. The results of the run were compromised by the decomposition of a plastic snorkel used in the condenser. PFs for both iron and niobium are both lower than in previous runs. Product yield was again reasonable compared to earlier runs.

Run 4 (1000 g) The hydrogen concentration used in Stage 2 of the protocol was varied between 5 – 20% in nitrogen. With the flowrate used, 5% H2 in N2 was too low as orange color (FeCl3) was observed to develop in the purified product. Increasing the hydrogen content to between 10 and 20% caused the orange color to disappear as product was collected. Iron PF is in line with previous results. The niobium PF could not be determined accurately and is low. The Nb mixing procedure for the starting ZrCl4 materials and NbCl5 was incorrect resulting in an in accurate (low) Nb concentration.

Conclusions and Prospects for a Technologically Relevant Recycling Strategy

The overarching goal of the project is to evaluate the potential for sublimation-based purification protocols to provide purified zirconium chloride derived from the impure and contaminated pro-ducts of the direct chlorination of Zircaloy claddings from spent nuclear fuel.

The purification strategy that we have developed begins with the categorization of the different types of impurities present in the feedstocks according to their volatilities relative to zirconium chloride (ZrCl4). Among the species present, iron chloride (FeCl3) and niobium oxychloride (NbOCl3) are identified to be potential problems in any sublimation-based protocols because their volatilities are very similar to zirconium ZrCl4. Two different chemical strategies have been developed to address the challenges posed by iron and niobium impurities. For niobium, a gas phase chlorination reaction using thionyl chloride (SOCl2) is used to deoygenate this species to product the pentachloride (NbCl5) which is significantly more volatile than ZrCl4 and can therefore be removed in a forerun in the protocol. An additional advantage to this chlorination strategy using thionyl chloride is the deoygenation-chlorination of nonvolatile zirconates (ZrOxCly) that would be otherwise lost in the process, thus reducing the yields. Hydrogen gas is used to reduce ferric chloride to the nonvolatile ferrous state so that purified ZrCl4 may be sublimed from the impure mixture.

Scaleup studies based on four separate runs indicate that the apparatus and purification protocol developed on small scales does scale reasonably well to 1000 g. Approximately 18 hours are required for each stage in the protocol. Stages 1 and 2 in the protocol are separated by a complete cool-down of the entire apparatus so that the sublimate condenser can be exchanged to separate the niobium rich forerun from the purified product.

Purification factors for niobium and iron are in the range of 30 – 100 while achieving overall yields of ZrCl4 of ~90%. Purification factors for Cs and Sr are high as they are nonvolatile under the sublimation conditions used and therefore remain in the residue after sublimation. Antimony

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appears to be transformed into the pentachloride which passes through the entire sublimation apparatus and must be caught in an external trap on the exhaust line.

Loss of product in the protocol occurs mainly during the collection of the forerun. While NbCl5 is at least ten times as volatile as ZrCl4, both are collected together in the forerun. Therefore, the conditions and the determination of the endpoint for the forerun are critical in obtaining high yields of the desired product in high purity.

The reduction of ferric chloride by hydrogen is well known and used extensively in industry to remove iron from metal chloride mixtures. Finding the optimum conditions for this step is not considered to be critical to the success of the purification protocol.

Research to Technology – Future Challenges

Early versions of the sublimation apparatus were constructed of both gas and different stainless steels (304, 316). Although the research literature indicates that stainless steels should be resistant to the conditions and reagents involved in these investigations[9] we observed that they were not. Specifically, early purification runs with a SS-304 top and 316-stainless steel valve between the sublimation pot and condenser showed clear evidence of corrosion of the steel surfaces and contamination of the product with iron. For this reason the steel parts were removed from the apparatus and replaced with glass (the valve was completely removed from the apparatus). The final apparatus that was tested both at small and large scales was virtually free of stainless steel (a Hastelloy coupling with graphite ferrules was used to mate the exhaust line from the sublimation bottom to the feed line of the condenser). While changing to glass addressed the immediate problem in our investigations, it does not solve this issue in future application. Metals (e.g Iconel or Monel steels) that are especially corrosion resistant are possible materials that should be investigated in the fabrication of large, to scale sublimation apparatuses.

The purification apparatus and associated protocol that are described here have one important shortcoming that will need to be addressed in technological applications. Determining of the endpoint of the forerun where niobium pentachloride is separated from zirconium chloride is difficult and relies mainly on the observation of a (sometimes subtle) visual change in the color of the sublimate (yellow to white) to decide when all the niobium has been collected in the forerun. In actual application with radioactive feedstocks, visual observation would have to be replaced with some type of remote sensor such as a camera or visible spectrometer that could be used to measure a reflectance spectrum and develop a spectroscopic signature for the endpoint. Based on our experiences, noninvasive monitoring of the progress of the forerun collection will be chal-lenging due in part to the nonregular manner in which solids form in the condenser. For this reason, we suggest samples be collected and analyzed to accurately determine endpoint of the forerun (no NbCl5 detected in condensate).

To facilitate real-time analysis of the sublimate, we suggest that a high temperature valve be placed on the transfer line between the sublime and condenser. With such a valve, the sublimation process could be paused without cooling the system to room temperature. After stopping flow through the system and isolating the sublimation apparatus in the furnace, the condenser could be disconnected from the system and samples taken for either direct spectrophotometric analysis or ICP-OES elemental analysis.

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Finally, antimony (presumably as SbCl5) still presents a problem in the context of sublimation-based purification strategies. When it is transformed into the pentachloride, it appears to be volatile enough for it to be carried through the entire system and into the exhaust stream where it must be captured via a trap. While reasonable purification factors for antimony have been achieved for the solid zirconium chloride product, system flow-through of a radiological impurity could represent a fundamental shortcoming of the purification strategy.

Figure 3 Purification protocol for 300g scaleup run

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Re‐chlorination

with SOCl2

Flow Rate (cc/m

in)

Temperature of Rea

ctor (°C)



Stage 1 Stage 2

16 h

4 h16 h


Collection of ZrCl4


Nitrogen

Thionyl Chloride/N2

100% Hydrogen

Temperature

Flows

Reduction of iron

6 h

15


0

50

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Nitrogen

Thionyl Chloride/N2

5 – 10% Hydrogen/N2

Temperature

Flows

Re‐chlorination with SOCl2 Reduction of iron –

collection of ZrCl4Flow Rate (cc/m

in)

Temperature of Rea

ctor (°C)



Stage 1 Stage 2

16 h

2 h

16 h




0

50

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Nitrogen

Thionyl Chloride/N2

50% Hydrogen/N2

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Flows

Re‐chlorination with SOCl2

Reduction of iron –collection of ZrCl4

Flow Rate (cc/min)

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ctor (°C)



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4 h

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16


0

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Nitrogen

Thionyl Chloride/N2

5 – 50% Hydrogen/N2

Temperature

Flows

Re‐chlorination

with SOCl2

Reduction of iron –collection of ZrCl4

Flow Rate (cc/m

in)

Temperature of Rea

ctor (°C)




Stage 1 Stage 2

16 h

4 h

16 h


17

A Quantum Chemistry Modeling Study of the Gas Phase Reactions of ZrCl4 and Metal Chlorides

Sublimation based purification strategies begin with the assumption that the metal chloride species act as ideal gases which do not interact with one another under sublimation conditions. When this assumption is valid, the volatilities of the metal chloride salts are given by the thermodynamic solid-gas phase equilibrium properties of the individual species involved. At any given temperature the major species in the gas phase can be predicted by vapor pressure – temperature data[1] and purification of one species from others may be achieved via protocols that selectively volatilize or hold back the desired component of the mixture.

Work by Schäfer[10], Papatheodorou[11], and others[12] in the 1970s and 80s conclusively show that many metal chloride species do not act as noninteracting ideal particles in the gas phase and frequently form oligomers. Schäfer’s group used Knudsen cell–mass spectrometry to identify and quantitatively measure the different metal chloride species present in the gas phase at equilibrium as a function of temperature. Papatheodorou and coworkers measured variable temperature, high pressure vibrational (Raman) spectra of zirconium tetrachloride in sealed quartz tubes and observed the reversable appearance of new bands which they assigned to the dimer Zr2Cl8. While the conditions of the two experiments are quite different[11b, 13], the derived thermodynamic results for dimerization equilibria for a number of metal chloride species agree reasonably well with one another.

Neither of these studies looked at the formation of heterometal dimers (or higher oligomers) of the sort that we wish to consider in these investigations. Furthermore, neither of these techniques provides detailed information about the structures of mixed metal species in the gas phase. For these reasons and to determine if such reactions might impact the sublimation behavior of mixtures of metal chloride species, we initiated a quantum chemical computational modeling study of potential oligomers and heterometal dimers formed in the reactions of zirconium chloride with metal chlorides derived from the alloying components of Zircaloys as well as some of the radiological contaminants that are present (e.g. Cs, Sr, Sb) in the cladding from spent nuclear fuel.

In the last twenty years, computational modeling of large, many electron species has progressed significantly such that it is now possible to model many electrons species containing multiple metal centers in reasonable amounts of time and obtain chemically relevant results. There are several reasons for this. First, the computationally efficient approximations and algorithms for many electron systems have been developed and refined such that “thermochemical accuracy” (i.e. molecular energy descriptions within 1 kcal/mole of measured thermochemical values) may now be achieved.[14] Second, Density Functional Theory (DFT) based models offer a reliable and inexpensive (computational time) approach to obtain reasonably accurate molecular energies (3 – 5 kcal/mole).[15] Third, a number of well-developed software suites are now available, that allow users to easily and rapidly build models of large and very complicated species as well as take advantage of massively parallel processing strategies to reduce the time required for modeling experiments. Finally, numerous protocols and programs allow easy and relatively inexpensive access to powerful computing facilities so that students and researchers can conveniently run jobs at a pace where results from theoretical modeling may be obtained quickly.

18

Schäfer studied the dimerization of many metal complexes in the gas phase.[10a] Halide ligands in general and chloride in particular readily engage in bridging dative covalent interactions with a second metal ion to increase the coordination numbers of the metal cations. The most common number of bridging ligands in such oligomers is two whereby both metal ions increase their coordination numbers (CNs) by one.

Two general observations from his work are: Coordinately unsaturated metal complexes in the gas phase are stabilized when they are able to increase their coordination numbers (CNs) through dative covalent, bridging ligand interactions (i.e. there is no direct M–M bonding). This is frequently observed for 3-coordinate metal species where they oligomerize to form polynuclear cluster complexes and increase their CNs to 4, 5, or 6. 4-coordinate species can oligomerize to form 5- and 6-coordinate species and 5-coordinate complexes can dimerize thereby achieving six coordination around the metal.

Gas phase oligomerization reactions involve significant energetic and entropic components. Coordinately unsaturated metal complexes are stabilized by increasing their CNs relative to their monomeric precursors. At the same time, oligomerization reactions in the gas phase suffer from significant entropic penalties (negative Δ𝑆). This entropic penalty generally falls in the range of 20 – 30 cal/molꞏK for the dimerization of two mononuclear species. Thus predicting the position of the equilibrium for these reactions depends on the relative magnitudes of the energetic and entropic terms in the equation for free energy, as well as the temperature.

∆𝐺 ∆𝐻 𝑇∆𝑆

Previous studies have focused mainly on the dimerization of identical metal species (homodimerization). In the context of this project we seek to determine if zirconium chloride reacts with other metal chloride species present from the chlorination of Zircaloy claddings and forms mixed metal species under sublimation conditions (600 – 700K; 𝑃 ~ 1 atm; 𝑝 𝑍𝑟𝐶𝑙 ~1 𝑎𝑡𝑚; 𝑝 𝑀𝐶𝑙 ≪ 1 ). If such adducts were favored, their presence in the sublimation could lead to chemical transport mechanisms whereby impurity metal chlorides are carried over into the product thus defeating the purification.[16]

Gas Phase Reactions of zirconium chloride and metal chlorides derived from Zircaloy direct chlorination reactions

Sublimation conditions are ~1 atmosphere total pressure and 600 – 700K. Zirconium chloride is the major component in the mixture and its vapor pressure in this temperature range will be approximated as 1 atm (sp 606K). The most important metal chloride impurities considered in the study are derived from alloying components of different Zircaloy claddings: FeCl3, NbCl5, NbOCl3 and SnCl4. The amounts of the other alloying metals in the feed should be small (<0.1 wt%) and are neglected. Radiological impurities are divided into two classes: actinides (e.g. U, Pu, Am, Np) and radioactive fission byproducts (137Cs, 125Sb, 90Sr). The actinide species are again

Z rZ rCl

Cl

ClCl Cl

Cl

Cl

ClCl

ZrCl Cl

Cl

2

19

neglected in this study because the adducts that they may form with zirconium chloride are assumed to have formula weights so high that they are not expected to be volatile. (This assumption is supported by experimental results of the project using cerium(III) chloride as a surrogate for the actinides.) .

We assume that during sublimation the species in the gas phase are in thermodynamic equilibrium with one another. Thus the question of whether mixed metal species form during sublimation may be reformulated into an evaluation of the equilibria that exists between monomeric and dimeric species as illustrated in the following chemical reaction.

𝑍𝑟𝐶𝑙 𝑀𝐶𝑙 ⇌ 𝑍𝑟𝑀𝐶𝑙

In the case of iron trichloride, the equilibrium equation must be reformulated in terms of the dimer which is known to be more stable than the monomer in the gas phase:

𝑍𝑟𝐶𝑙 12

𝐹𝑒 𝐶𝑙 ⇌ 𝑍𝑟𝐹𝑒𝐶𝑙

Quantum chemical (QC) models initially give the electronic energies of each of the species in the above equations. Well known, standard equations can then be used to transform QC electronic energies and vibrational frequencies into thermodynamic heats and entropies of formation from whence free energies may be derived.[17] With free energies of formation for each species, free energies of reaction and equilibrium constants can then be calculated straightforwardly. In all the reactions studied, reaction free energies were far from zero and therefore clear answers to the questions posed above are obtained without requiring detailed consideration of equilibrium constants or estimates of the partial pressures of species during sublimation.

Very little information about the structures of the dimers is known. Papatheodorou and coworkers studied both the dimerization of zirconium chloride and ZrCl4 with aluminum trichloride.[11] Based on an analysis of gas phase Raman spectra these authors proposed that both the Zr2 and ZrAl adducts have three bridging chloride ligands and that the C3v structure for the ZrAl adduct was most likely the structure of the adduct.

Computational models offer the possibility of more clearly identifying the correct structures of these types of adducts in two ways. First, the relative energies each of the isomers above are obtained from the calculations. Thus, the lowest energy structure may be identified if the energy differences are larger than the error associated with the level of modeling chosen. Second, once an optimized structure is obtained, a complete vibrational spectrum can be calculated and compared with experimental data to see if the predicted correspondence is observed. As will be described, both of these results have been obtained in these modeling studies.

Initial Considerations To begin this quantum chemical study the assumption was made that all reactions occur in the gas phase. No solid ⇌ gas reactions or equilibria were included in the models described here. It should

Z r

Cl

ClClAlCl

Cl

ClClZ rAl

Cl

Cl

Cl

ClClCl

ClZ r

Cl

Cl

Cl AlCl

Cl

ClCl

C3vCsCs

20

be noted here that while thermodynamic reaction free energies may used to predict that one or the other side of the equilibrium is favored, the volatilities of the species are not considered. Below 500K the volatilities of all species in these mixtures become so small that regardless of the computational outcomes for equilibria, no appreciable material transfer from the sublimation will occur. Therefore, the question of chemical transport and contamination of the produce is limited to sublimation temperature (600K) and above.

Quantum chemical models of third row transition metal complexes with chloride ligands contain large number of electrons which can lead to excessively long computational times (~weeks/run), especially when wavefunction-based models are employed. Therefore, modeling was begun at the DFT level of theory which normally requires considerably less computational time (~24 hr/run).

Computational Resources used in the project Computations were initiated on the University of Tennessee Computational Cluster Newton as opportunistic users. The Gaussian 09 quantum chemistry package[18] was initially used for model building. A decision was made to switch to the program TURBOMOLE[19] with enhanced parallelized computational algorithms. Most of the computational results obtained with Gaussian 09 were reproduced within computational error with TURBOMOLE before discontinuing modeling efforts with Gaussian 09.

Energy and gradient calculations were carried out at different levels of theory (DFT or WFT) and the number of required node(s)/processor combinations varied. Depending on the size of the system (number of electrons) a particular node/processor set was chosen mainly based on the available memory per node. A typical DFT calculation utilized one node with its full complement of processors available for that node with memory of ~128 GB per node. At the WFT level, in addition to processor speed, memory available to the node is critically important (as much as possible; ~1 TB).

Basis Set Choice Weigend and Ahlrichs introduced the DEF2 family of basis sets which provides consistent accuracy across the periodic table.[20] The DEF2-TZVP basis set was chosen from this family. DEF2- designates the second generation default basis set with triple zeta valence quality (TZV). P denotes partial polarization corrections are included. The corresponding quadrupole zeta valence level basis set was also tested and found to give nearly identical energies (≤ 1 kcal) as the TZV sets. Therefore, the TZV basis set was chosen. Small core, effective core potentials (ECP) were used for heavier atoms (4th row metals) to reduce the number of basis functions used in the calculations therefore reducing computational work. We utilized the DEF2-ECP which improved the quality of the electronic structure calculation by incurporating scalar relativistic effects for the heavy elements.

All closed shell species (e.g. ZrCl4, NbCl5, AlCl3, SnCl2, SbCl5) were modeled with Restricted Hartree-Fock (RHF) theory (no unpaired electrons). The aluminum/iron adduct (AlFeCl6), FeCl3 and the dimer Fe2Cl6 were modeled with Unrestricted Hartree-Fock (UHF) theory (unpaired electrons). Metals from the 3d block are typically high spin species and follow the Aufbau principal filling lower energy orbitals first. Since the equilibrium energies of the monomer/dimer

21

iron chloride species are known, calculations were performed on these adducts assuming different high/low spin states to determine the proper spin multiplicity. Calculations confirmed the FeCl3 species (high spin) has a multiplicity of 2S +1=6 so that the total spin S=5/2 represents 5 unpaired electrons while the dimer, Fe2Cl6 (high spin) has a total spin of S=5 (10 unpaired electrons). In the case of adduct formation involving AlCl3 and FeCl3 (5 unpaired electrons, high spin), the spin multiplicity was confirmed to be S=6. Similar results were obtained for ZrFeCl7.

Benchmarking and Choice of DFT Functional In DFT, the functional describes the electron density which is a function of coordinate space and time. All functionals used in practice are approximations and there are many different functionals available which are suitable for any particular study.[15, 20b, 21] These functionals may be separated in four levels of approximation:

The local density approximation (LDA) is the basis of all approximate exchange-correlation functionals. This model revolves around the idea that the exchange energy depends only on the density at a point and is that of the uniform electron gas of that density.[21] LDA is the simplest density functional but is insufficient for accurate chemical calculations as it typically overbinds molecules.[22]

Generalized gradient approximations (GGA) are functionals that utilize both the density and the gradient of the density at each point to account for inhomogeneities in the density. GGA’s give improved results relative to LDA’s but are still not necessarily accurate, partially due to the fact that exchange potential doesn’t necessarily have the correct qualitative behavior. Popular GGA’s include PBE and BLYP.[21]

Meta-GGA’s perform as well as GGA’s but improve in areas such as thermochemistry and kinetics. These functionals incorporate GGA and a portion of the kinetic energy density. Popular examples of meta-GGA functionals are TPSS and M06-L.[21]

Hybrid functionals replace some fixed fraction of GGA exchange with Hartree-Fock exact exchange. By mixing in only a fraction of exact exchange one can mimic effects of static correlation and produce a highly accurate functional. Computationally, the cost is higher because exact exchange depends not only on the electron density but also on the density matrix. Well known hybrid DFT functionals are B3LYP, PBE0, M06 and M06-2X. Methods including electron correlation functions into a calculation rely heavily on basis sets which are crucial to enhance accuracy, but at higher computational cost.

22

A survey of DFT functionals was conducted using experimental values found in the literature for a number of metal chloride dimers (Table 5) to determine the most appropriate functional for modeling the metal chloride species in this study.

Based on the individual values found in Table 5 as well as the averaged absolute error for each, the Mn12-SX, M06, and M06-2X and functionals are all within computational error of one another and any could be used. Subsequent DFT calculations were carried out using the M06-2X functional. It should be noted however that while average errors recorded for DFT calculations are well within accepted limits (3 – 5 kcal), outliers are frequently observed (e.g. ZrCl4, NbCl5). Given the importance of these two species in particular, we decided to develop parallel, independent wavefunction-based models of the gas phase equilibria involved in this project.

WFT calculations were carried out using the TURBOMOLE program utilizing the equilibrium geometries obtained from DFT optimized models with the M06-2X/Def2-TZVP functional/basis set combination. The coupled cluster (CC) wavefunction based correlation method was used to further optimize the equilibrium geometries of the structures. Harmonic vibrational frequencies were obtained from the second derivatives of analytical gradients which lead to the thermo-chemical corrections. The double excitations implemented in CC2 calculations account for dynamic electron–electron correlation, but at a high computational cost for species with many valence electrons (transition metals). Spin-opposite scaling of electron pair contributions has been shown to be an effective tool in reducing the computational cost as well as improve the accuracy of the scaling factors necessary for harmonic vibrational frequencies.[23] The SOS-CC2 variant[24] was used for 4d metals which completely neglects the same-spin components while scaling the opposite-spin pairs to mimic the absence of same-spin correlations yielding accurate and efficient calculations.

Table 5 Summary of DFT Benchmarking study with six different Functionals Δ(ΔH) is the difference between the DFT value for the reaction shown on the left and experimental values found JANAF tables, NIST thermochemical data base; Shafer et al., 1974-76; S. Boghosian et al., 1986, 1989

All values in kcal

1 atm 298 KLiterature B3LYP revTPSS TPSSH MN12‐SX M06 M06‐2X

ΔH Δ(ΔH) Δ(ΔH) Δ(ΔH) Δ(ΔH) Δ(ΔH) Δ(ΔH)

2 ZrCl4 ⇄ Zr2Cl8 ‐13.53 11.53 9.21 10.82 5.54 6.16 4.80

ZrCl4 + ½ AlCl3 ⇄ ZrAlCl7 ‐9.99 10.93 3.84 5.69 1.25 2.24 0.26

2 AlCl3 ⇄ Al2Cl6 ‐30.25 9.02 2.17 3.06 2.31 3.26 ‐0.49

2 FeCl3 ⇄ Fe2Cl6 ‐35.40 9.64 5.61 6.77 2.52 ‐0.39 ‐2.77

½ FeCl3 + ½ AlCl3 ⇄ FeAlCl7 0.00 ‐0.94 ‐1.31 ‐1.06 ‐0.36 ‐0.83 ‐0.56

2 NbCl5 ⇄ Nb2Cl10 ‐21.51 25.10 14.87 17.51 10.22 11.70 11.35

Averaged “absolute” error

from literature values11.19 6.17 7.48 3.70 4.10 3.37

23

All WFT calculations were performed with the augmented correlation-consistent polarized valence triple zeta (aug-cc-pVTZ) basis set.[25] For species containing row five elements, the relativistic effective core potential (RECP) aug-cc-pVTZ-PP[26] basis set was used. Geometries optimized at the CC2/aug-cc-pVTZ level were subjected to single point CCSD(T) calculations with the aug-cc-pVTZ basis set. The highly accurate coupled cluster singles and doubles with noniterative triple excitations, CCSD(T), considers the nondynamic correlation effects (i.e. orbital relaxation effects) and includes contributions from triple excitations for quantitative accuracy.[27]

Results

The results of these modeling studies will be presented in two parts. The first addresses the main aim of the project, that being are mixed metal dimer species important in the gas phase under sublimation conditions. The second part will be a brief description of other results from these modeling studies including structural descriptions of potential gas phase adducts as well as computational predictions of the vibrational spectra of gas phase species.

Part 1 – Thermochemical Evaluation of the dimerization of gas phase metal chlorides with zirconium chloride

𝑍𝑟𝐶𝑙 𝑀𝐶𝑙 ⇌ 𝑍𝑟𝑀𝐶𝑙

DFT and wavefunction based models for each of the species in the above equation were developed. All models represent well converged, stable, optimized structures for all species. The electronic energies were corrected for zero point energy effects and used in standard thermochemical equations[17] to obtain enthalpies and entropies of formation for each species. Thermodynamic functions for enthalpy, entropy and free energy were calculated as a function of temperature from 298 to 600K.

Table 6 presents a numerical comparison of benchmarking results from DFT and Wave Function Theory (WFT) models developed in this work. The 1.24 kcal average absolute error for WFT models is close to chemical accuracy but again, outliers such as NbCl5 and GaCl3 should not be ignored. In general, DFT and WFT results are quite close to values in the literature with WFT results being slightly better on average.

Having established the accuracy of both DFT and WF modeling approaches with a series of dimerization reactions similar to those of interest in this study, models were developed for adduct formation between zirconium tetrachloride and other metal chlorides derived from zircaloy cladding. The reaction free energies are summarized in Table 7 at 600K which is the low temperature limit for the sublimation protocols developed in this project. The main points of interest are the following:

1. The formation of chloride-bridging dimers with zirconium chloride with Zr, Fe, Nb, and Sb are all highly disfavored at 600K.

2. Monomeric chlorides are all energetically stabilized by the formation of chloride bridges but also suffer an entropic penalty via the reduction of the number of independent particles in the gas phase. The entropic penalty overwhelms the energetic stabilization experienced

24

in the formation of the dimer relative to the two monomers at 600K such that dimerization is disfavored at this temperature.

Figures 7 – 11 illustrate the behavior of the temperature dependence of the equilibrium constant (Kp) enthalpy, entropy and the entropic penalty term in the free energy equation for the gas phase reactions of ZrCl4 with FeCl3, NbCl5, SbCl5.

Equilibria(chloride ligands not shown)

All values in kcal at 298K

2 Al ⇄ Al22 Fe ⇄ Fe2

2 Zr ⇄ Zr2

2 Nb ⇄ Nb2

2 Sn ⇄ Sn2

2 Ti ⇄ Ti22 In ⇄ In2

2 Ga ⇄ Ga2

Zr + ½ Al2 ⇄ ZrAl½ Al2 + ½ Fe2 ⇄ AlFe

M06-2X

Def2-TZVP

∆(∆H)‒0.49‒2.77+4.80+11.35‒1.10+2.67+0.01‒0.41+0.26-0.56

Averaged error from literature values 2.44 1.24

CCSD(T)

aug-cc-pVTZ

∆(∆H)‒ 0.21+ 1.40+ 0.08+ 3.73‒ 1.13-0.10‒ 1.41‒ 3.01+0.71-0.66

Table 6 Benchmarking comparison of DFT (M06-2X) and WFT (CCSD(T)) results. Literature thermochemical values from: JANAF tables, NIST thermochemical data base; Shafer et al., 1974-76; S. Boghosian et al., 1986, 1989

† Triple chloride bridge ** oxo bridge

Table 7 Summary of thermodynamic results for the heterodimerization of ZrCl4 and different metal chlorides. All adducts two chloride bridging ligands unless otherwise noted.

CCSD(T) / aug-cc-pVTZAll values in kcal at 600 K

∆G ∆H -T∆S

Zr2Cl8 8.94 -12.23 21.18

ZrFeCl7† 4.25 -6.69 10.94

Fe2Cl6 -11.22 -32.68 21.46

ZrNbCl9† 4.12 -21.88 26.00

Nb2Cl10 9.79 -16.56 26.35

ZrNbOCl7 13.78 -8.31 22.09

Nb2O2Cl6** 12.27 -12.75 25.02

ZrSbCl9† 9.17 -17.66 26.83

Sb2Cl10 19.50 -6.75 26.25

25

‐30

‐20

‐10

0

10

20

30

ΔG

, kcal

Temperature (K)

ZrNbCl9

ZrSbCl9

Zr2Cl8

Nb2Cl10

ZrFeCl7

ZrNbOCl7

Sb2Cl10

Fe2Cl6

Nb2O2Cl6

300 400 500 700 T (K)600

Temperature DependenceFree Energies (∆G) of dimerization

Sublimation temperature range

Figure 7 Temperature dependence of free energy for dimerization reactions between ZrCl4 and metal chlorides in the gas phase (WFT results).

Figure 8 Temperature dependence of the equilibrium constant for the reaction of ZrCl4 with Fe2Cl6 and NbCl5 in the gas phase (WFT results).

‐12.0

‐10.0

‐8.0

‐6.0

‐4.0

‐2.0

0.0

2.0

4.0

6.0

Ln Kp

Kp vs Temperature

Sublimation temperature

range

300400500 T (K)600700

Kp = 1.3 E‐4

Kp = 2.3 E‐3

ZrNbCl9

ZrFeCl7

26

‐40

‐35

‐30

‐25

‐20

‐15

‐10

‐5

0

ΔH

, kcal

Enthalpy of Reaction (ΔH) vs Temperature


300 400 500 700 T (K)600

ZrNbCl9

ZrSbCl9

Zr2Cl8Nb2Cl10

ZrFeCl7 ZrNbOCl7

Sb2Cl10

Fe2Cl6

Nb2O2Cl6

Figure 9 Temperature dependence of the reaction enthalpy for the reaction of ZrCl4 with metal chlorides in the gas phase (WFT results).

Figure 10 Temperature dependence of the reaction entropy for the reaction of ZrCl4 with metal chlorides in the gas phase (WFT results).


‐50.00

‐45.00

‐40.00

‐35.00

‐30.00

‐25.00

‐20.00

200 300 400 500 600 700 800

Entropy (cal/m

ol K

)

Temperature (K)

Entropy of Reaction (ΔS) vs Temperature

ZrNbCl9

ZrFeCl7

27

5

10

15

20

25

30

‐TΔS (kcal/mol)

Entropic Penalty of Reaction (‐TΔS) vs Temperature


300 400 500 700 T (K)600

ZrNbCl9

ZrSbCl9

Zr2Cl8

Nb2Cl10

ZrFeCl7

ZrNbOCl7

Sb2Cl10Fe2Cl6

Nb2O2Cl6

Figure 11 Temperature dependence of the TΔS term in the free energy equation for the reaction of ZrCl4 with metal chlorides in the gas phase (WFT results).

28

Part 2: Supplemental Results from Computational Modeling Studies

One of the benefits of computational modeling in this context is the ability to calculate how the different thermodynamic parameters change as a function of the state variables of the system. The temperature dependence of these reactions is of interest. Figure 12 Results of wave function theory geometry optimizations at two different temperatures for ZrFeCl7 in the gas phase. One of the doubly-bridged structures (green) always isomerizes during geometry optimization to the other, more stable doubly-bridged structure (blue) and is therefore not shown in the diagram.shows the temperature behavior of the free energy from room temperature 300 K to 700 K. It can be clearly seen that as the temperature decreases the magnitude of the entropy term (TΔS) decreases significantly such that at room temperature most reaction free energies close to zero and significant amounts of dimers could form under these conditions. It should be kept in mind, however, that neither the monomers nor dimer adducts are expected to have any significant vapor pressure at 298K and therefore, regardless of what is predicted thermodynamically. There will be effectively no metal chloride species in the gas phase at room temperature.

Structures of metal chloride dimerization adducts in the gas phase

ZrFeCl7 Scheme 1 shows one possible dimerization product from the reaction of ZrCl4 with FeCl3. The chloride ligands acting as the Lewis bases donating electrons to the Lewis acidic metal cations (Fe, Zr) forming the binuclear heterometal adduct. A number of questions may be asked about the products of this type of reaction. First, how symmetrically are the two bridging chloride ligands “shared” between the two metal centers? Second, how many chloride bridges are formed in the adduct. Third, what is the overall structure/symmetry of the adduct? Finally, which of several possible structures is the lowest energy form of the adduct? Gas phase spectroscopic studies such as those of the Papatheodorou group and mass spectrometric measurements of Schäfer provide little information to address these questions. Quantum chemistry modeling can, in general, address all of them.

Fe

Cl

Cl Cl

+ ZrCl

ClCl

Cl

Z rFeCl

Cl

Cl

Cl

Cl

Cl

Cl

Scheme 1 Potential Lewis acid-base adduct with ZrCl4

29

From the work of Schäfer[10a] it is known that tetrahedral and octahedral coordination geometries are favored by metal chloride species in the gas phase. For example, assessing the reactants of Scheme 1 at sublimation conditions, the iron will be in its dimeric state (Fe2Cl6) and can react with ZrCl4 to produce the mixed-metal adducts as seen in Scheme 2.

There are four possible structures for the ZrFeCl7 adduct; two structures have dichloride bridges (top) displaying Cs symmetry with a combination of 4- and 5-coordinate metal centers. The second structure type (bottom two) has three chloride bridges having either Cs or C3v symmetries. The zirconium and iron centers either have (5, 5) or (4, 6) coordination geometries about the metal centers.

The results of calculations at the WFT level for ZrFeCl7 are shown in Figure 12. The 4-, 5-coordinate (Fe, Zr) doubly bridged structure is slightly favored over the triply bridged structures with a free energy of formation (∆G) of 4.25 kcal at 600 K. However, the energy gap between these species is within the WFT benchmarked error (1.25 kcal) therefore an order of structures cannot be conclusively determined from out modeling efforts. At higher temperatures (1200 K) the different structural isomers begin to separate themselves in energy with one of the triply bridging isomers becoming significantly higher in energy than the others. The trend of losing bridging chloride ligands is follows at even higher temperatures (not shown) where the energies of all triply bridged species become higher than the doubly bridged ones. Fewer bridging chloride bonds will exist as the temperature is increased until ultimately monomers will be formed at high temperatures (>700K).

Scheme 2 Illustration of the different possible heterodimers (Fe-Zr) that may be formed in the gas phase.

Cl CsZ rFe

Cl

Cl

ClCl

Cl

Cl

C3vZ rFeCl

ClCl Cl

Cl

ClCl

CsZ rFe

Cl

Cl

Cl

Cl Cl

ClCl

+ZrCl

ClCl

Cl

FeFeCl

Cl

Cl

Cl Cl

Cl

1/2

ClCs

Z rFeCl

Cl

ClCl

Cl

Cl

30

Asymmetric chloride bridges Figure 13 illustrates a common feature in all the geometries of the dimeric species investigated here: asymmetric chloride bridges. Both DFT and WFT clearly show that the chloride ligands bridge the two metal asymmetrically in the ZrFeCl7 species in the gas phase; there is always one short and one long dative covalent bond from each bridging chloride ligand to the two metal centers. The metal-metal separations are always long (3.64 Å) indicating no metal–metal bonding exists. Previous spectroscopic techniques have not provided detailed information about the structures of mixed-metal adducts.

Figure 13 Illustration of the optimized geometry for the ZrFeCl7 mixed metal adduct from wave function theory models. The Zr-Cl long dative covalent bond is 2.56 Å. The short Zr-Cl bond is 2.67 Å. Zirconium is blue. Chlorine is green and iron orange.

7 ( )

ZrFeCl7 (μ‐Cl)2 (g)

ZrFeCl7 (μ‐Cl)3 (g)4.25

4.85

ZrCl4(g) + ½ Fe2Cl6(g)

600 K

Gib

bs F

ree

Ene

rgy

(kc

al)

Z rFe

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Z rFe

Cl

ClCl

ClCl

Cl

ClZ rFe

Cl

Cl

Cl

Cl Cl

Cl

ClZ rFeCl

ClCl Cl

Cl

ClCl


ZrFeCl7 (μ‐Cl)2 (g)


15.94


1200 K

Figure 12 Results of wave function theory geometry optimizations at two different temperatures for ZrFeCl7 in the gas phase. One of the doubly-bridged structures (green) always isomerizes during geometry optimization to the other, more stable doubly-bridged structure (blue) and is therefore not shown in the diagram.

31

Molecular Vibrations of mixed metal adducts: ZrMClx All geometry optimizations and frequency calculations were performed initially under C1 symmetry to remove any symmetry constraints and allow the molecule to access both higher and lower symmetries when searching the potential energy surface (PES). When the low energy structure closely approximated a higher symmetry structure, the calculation was repeated under the appropriate point group constraints and the energies of the two structures compared. The lowest energy structure was optimized to tight convergence levels (ΔE ≤ 0.1000E-07) both at the DFT and Coupled Cluster (WFT) levels of theory. The analytical gradients obtained from the geometry optimizations allow calculation of the second derivatives of total energies from whence vibrational frequencies are obtained. The accuracy of either computational approach (DFT, WFT) are assessed by comparing calculated vibrational frequencies with experimental data.

Table 9 summarizes the vibrational frequencies obtained from both of DFT and WFT (CC2 level) models as well as experimental data from the literature for zirconium chloride (ZrCl4). The errors shown in (∆ν in cm-1) represent differences between each model and the experimental data. ZrCl4 has a tetrahedral geometry with nine normal modes of vibration.

The vibrational frequencies determined by DFT and WFT are in good agreement with each other and the experimental data when available. One of the short comings of CC2 frequency calculations is that calculated vibrational frequencies are typically low[28] which matches our findings in this study. Results from DFT models are slightly better than WFT based on average differences from experimental data of 6.8 cm-1 for ZrCl4 with the largest difference being 11.2 cm-1. Ab initio methods use both mathematical and harmonic oscillator approximations to compute these frequency values. The difference between the true potential and the harmonic potential tends to cause the frequency values to be ~10% high which is compensated for by applying a scaling factor of 0.984[29] for M06-2X and 0.9614[30] for CC2.

ZrCl4

In the structure, zirconium is blue and chlorine is green.

Figure 14 Illustrations of the tetrahedral structure of ZrCl4 from WFT computational models. Zirconium is blue and chorine is green

32

Table 8 Calculated and Experimental bond angles for ZrCl4 in the gas phase

van der Vis, M. G. M.; Cordfunke, E. H. P.; Konings, R. J. M., Thermochemical properties of zirconium halides: a review. Thermochimica Acta 1997, 302 (1), 93-108.

Table 9 Calculated and Experimental vibrational frequencies for ZrCl4

Shimanouchi, T., Tables of Molecular Vibrational Frequencies Consolidated Volume II, J. Phys. Chem. Ref. Data, 1972, 6, 3, 993-1102.

Zr2Cl8

ZrCl4

Td

Experimental (angle, º)

Computational M06-2X (DFT)

(angle, º)

Computational CC2 (WFT)

(angle, º)

Difference (angle, º)

DFT– Exp.

Difference (angle, º)

WFT – Exp.

Cl-Zr-Cl

109.28 109.5 109.5 0.22 0.22

ZrCl4 Mode Experimental

Frequency (ν /cm-1)


( ν /cm-1)


( ν /cm-1)

∆νerror

DFT – Exp. (cm-1)

∆νerror

WFT – Exp.

(cm-1)

Td

1 A1 377 ± 3 366.6 360.9 -10.4 -16.1

2 E 98 ± 3 100.2 92.8 2.2 -5.2

3 T2 418 ± 6 406.8 410.4 -11.2 7.6

4 T2 113 ± 6 109.8 102.2 -3.2 -10.8

Averaged absolute error from Literature value 6.8 9.9

Figure 15 Illustrations of the tetrahedral structure of Zr2Cl8 from WFT computational models. Zirconium is blue and chorine is green.

33

Table 10 Calculated and Experimental bond lengths for Zr2Cl8 in the gas phase

Table 11 Calculated and Experimental bond angles for Zr2Cl8 in the gas phase

Zr2Cl8 Atoms Computational

CC2 (WFT) (Å)

C2h

Cl(6)-Zr(8) 2.692Cl(5)-Zr(1) 2.692 Cl(10)-Zr(8) 2.337 Cl(9)-Zr(8) 2.332Zr(8)-Cl(5) 2.501 Zr(8)-Cl(7) 2.332Cl(6)-Zr(1) 2.501 Cl(4)-Zr(1) 2.337 Cl(3)-Zr(1) 2.332Cl(2)-Zr(1) 2.332

Zr2Cl8 Atoms Computational

CC2 (WFT) (angle, º)

Atoms Computational

CC2 (WFT) angle, º)

C2h

Zr(8)-Cl(6)-Zr(1) 103.3 Zr(8)-Cl(5)-Zr(1) 103.3 Cl(7)-Zr(8)-Cl(9) 113.0 Cl(2)-Zr(1)-Cl(3) 113.0

Cl(7)-Zr(8)-Cl(10) 100.4 Cl(2)-Zr(1)-Cl(4) 100.4 Cl(7)-Zr(8)-Cl(6) 87.2 Cl(2)-Zr(1)-Cl(6) 121.6 Cl(7)-Zr(8)-Cl(5) 121.6 Cl(2)-Zr(1)-Cl(5) 87.2



34

Table 12 Calculated vibrational frequencies and structure of Zr2Cl8. The Zr2Cl8 dimer (C2h symmetry) exhibits 24 normal modes of vibrations. A partial Raman spectrum has been reported for Zr2Cl8 at high temperature (723 – 773 K) and pressure (25 – 40 atm).[11a] The two calculated Raman bands (DFT, WFT) are in good agreement with experimental data.

M. Photiadis, G.; N. Papatheodorou, G., Vibrational modes and structure of liquid and gaseous zirconium tetrachloride and of molten ZrCl4-CsCl mixtures [double dagger]. J. Chem. Soc., Dalton Trans, 1998, (6), 981-990.

Zr2Cl8 Mode Experimental



( ν /cm-1)


( ν /cm-1)

∆νerror

DFT – Exp. (cm-1)

∆νerror

WFT – Exp. (cm-1)

C2h

1 Au 15.5 2 Au 24.1 23.7 3 Bg 46.0 41.9 4 Ag 51.6 51.6 5 Bu 72.3 69.8 6 Ag 85.0 84.2 7 Bu 93.9 91.9 8 Bg 96.3 92.0 9 Ag 115.1 111.3

10 Au 120.8 116.0 11 Bg 123.3 118.9 12 Au 130.4 125.8 13 Bu 135.1 129.3 14 Ag 145.2 140.3 15 Bu 207.6 208.3 16 Ag 218.3 220.0 17 Ag 310 302.0 295.1 -14.918 Bu 312.2 304.1 19 Bu 388.8 376.0 20 Ag 392.0 381.8 21 Ag 404 405.7 390.8 13.2 22 Bu 411.2 398.6 23 Bg 411.8 406.1 24 Au 416.7 410.4

35

ZrNbCl9

Niobium chloride does not exist in the dimeric state at sublimation conditions[31] and the ZrCl4 will only react with the NbCl5 monomer to form the di-adduct (Scheme 3). The reactants, ZrCl4 and NbCl5, have tetrahedral and five-fold coordination geometries, respectively and form the ZrNbCl9 adduct with both the metal centers having octahedral coordination with three bridging chlorides and three terminal chlorides on each metal center.

The optimized (WFT) structure is shown in and frequency table are shown in together below.

Table 13 WFT Bond Lengths for ZrNbCl9

ZrNbCl9 Atoms Computational

bond length (Å)

C1

Cl(11)-Zr(1) 2.342Cl(10)-Zr(1) 2.342 Cl(9)-Zr(1) 2.342 Cl(8)-Nb(2) 2.278Cl(7)-Nb(2) 2.278 Cl(6)-Nb(2) 2.278Cl(5)-Nb(2) 2.502 Cl(4)-Nb(2) 2.501 Cl(3)-Nb(2) 2.502Cl(5)-Zr(1) 2.686 Cl(4)-Zr(1) 2.687 Cl(3)-Zr(1) 2.686

Nb

Cl

Cl Cl

Cl Cl

+ ZrCl

ClCl

Cl

Z r

Cl

Cl

ClNb

Cl

Cl

Cl

Cl

Cl

Cl

Scheme 3 Lewis acid-base reaction between ZrCl4 and NbCl5

Figure 16 Illustration of the optimized structure of ZrNbCl9 . Zirconium is blue, niobium is dark grey and chorine is green

36

Table 14 Table of bond angles for ZrNbCl9 from WFT theory model. No experimental data has been reported for this species.

ZrNbCl9 Atoms Computational bond angle (º)

Atoms Computational bond angle (º)

C1

Zr(1)-Cl(5)-Nb(2) 88.061 Zr(1)-Cl(3)-Nb(2) 88.062Zr(1)-Cl(4)-Nb(2) 88.056 Cl(9)-Zr(1)-Cl(10) 102.497 Cl(6)-Nb(2)-Cl(7) 98.498 Cl(9)-Zr(1)-Cl(11) 102.508 Cl(6)-Nb(2)-Cl(8) 98.502 Cl(9)-Zr(1)-Cl(3) 90.074Cl(6)-Nb(2)-Cl(5) 167.075 Cl(9)-Zr(1)-Cl(4) 90.067 Cl(6)-Nb(2)-Cl(3) 89.912 Cl(9)-Zr(1)-Cl(5) 159.617Cl(6)-Nb(2)-Cl(4) 89.916 Cl(10)-Zr(1)-Cl(11) 102.510 Cl(7)-Nb(2)-Cl(8) 98.491 Cl(10)-Zr(1)-Cl(3) 159.628 Cl(7)-Nb(2)-Cl(5) 89.891 Cl(10)-Zr(1)-Cl(4) 90.079Cl(7)-Nb(2)-Cl(3) 89.896 Cl(10)-Zr(1)-Cl(5) 90.086 Cl(7)-Nb(2)-Cl(4) 167.056 Cl(11)-Zr(1)-Cl(3) 90.095 Cl(8)-Nb(2)-Cl(5) 89.898 Cl(11)-Zr(1)-Cl(4) 159.640Cl(8)-Nb(2)-Cl(3) 167.065 Cl(11)-Zr(1)-Cl(5) 90.098 Cl(8)-Nb(2)-Cl(4) 89.908 Cl(3)-Zr(1)-Cl(4) 73.744 Cl(5)-Nb(2)-Cl(3) 80.235 Cl(3)-Zr(1)-Cl(5) 73.756Cl(5)-Nb(2)-Cl(4) 80.239 Cl(4)-Zr(1)-Cl(5) 73.750 Cl(3)-Nb(2)-Cl(4) 80.245

37

Table 15 Vibrational frequencies and structure of ZrNbCl9

Computationally derived vibrational spectra for other known (when available) and unknown species investigated in this work are summarized Supplemental Tables and Figures to this report.

ZrNbCl9 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

C1 symmetry

1 42.3 40.1

2 56.0 58.8

3 56.5 59.0 4 63.8 69.8

5 74.9 70.3 6 79.2 72.4

7 96.3 96.5

8 108.4 107.1 9 110.8 107.3

10 124.5 121.2

11 126.7 121.6 12 141.8 140.1

13 164.9 162.3

14 166.5 162.4 15 168.5 162.6

16 190.9 198.5 17 192.1 198.8

18 247.7 252.4

19 252.0 252.6

20 253.7 257.8

21 312.3 312.6

22 370.7 372.8

23 374.0 378.8

24 379.9 379.6

25 397.7 389.6

26 402.3 403.8

27 407.5 404.0

38

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31. (a) Roeper, D.; Pandya, K.; Cheek, G. T.; O'Grady, W., An XAFS Study of Niobium Chloride in the Ionic Liquid 1-Ethyl-3-Methyl Imidazolium Chloride/Aluminum Chloride. ECS Trans. 2009, 16, 53-60. ; (b) Rosenkilde, C.; Voyiatzis, G.; Jensen, V. R.; Ystenes, M.; Oestvold, T., Raman Spectroscopic and ab initio Quantum Chemical Investigations of Molecules and Complex Ions in the Molten System CsCl-NbCl5-NbOCl3. Inorg. Chem. 1995, 34, 4360-4369.

41

Supplemental Tables and Figures of Quantum Chemical Models of Metal Chloride Species Investigated in this Project

Table of Contents

Page number

Vibrational frequencies and structural parameters of SbCl5 42

Vibrational frequencies and structural parameters of Sb2Cl10 44

Vibrational frequencies and structural parameters of ZrSbCl9 47

Vibrational frequencies and structural parameters of AlCl3 50

Vibrational frequencies and structural parameters of Al2Cl6 51

Vibrational frequencies and structural parameters of NbCl5 53

Vibrational frequencies and structural parameters of Nb2Cl10 55

Vibrational frequencies and structural parameters of FeCl3 58

Vibrational frequencies and structural parameters of Fe2Cl6 59

Vibrational frequencies and structural parameters of ZrFeCl7 (3 Cl bridge) 62

Vibrational frequencies and structural parameters of ZrFeCl7 (2 Cl bridge) 65

Vibrational frequencies and structural parameters of NbOCl3 68

Vibrational frequencies and structural parameters of Nb2O2Cl6 70

Vibrational frequencies and structural parameters of ZrNbOCl7 73

42

Vibrational frequencies and structural parameters of SbCl5. In the structure, antimony is purple and chorine is green.

Shimanouchi, T., Tables of Molecular Vibrational Frequencies Consolidated Volume II, J. Phys. Chem. Ref. Data, 1972, 6, 3, 993-1102

Hargittai, M., The molecular geometry of gas-phase metal halides. Coordination Chemistry Reviews 1988, 91, 35-88.

SbCl5 Mode Experimental

Frequency

(ν /cm-1)


( ν /cm-1)


( ν /cm-1)

∆νerror

DFT –

Exp. (cm-1)

∆νerror

WFT –

Exp. (cm-1)

D3h

1 A1 357 ±6 357.1 371.7 0.1 14.7

2 A1 307 ±6 302.1 304.7 -4.9 -2.3

3 A2 384 ±6 375.8 382.0 -8.2 -2.0

4 A2 154 ±15 169.7 187.5 15.7 33.5

5 E 398 ±6 397.1 410.7 -0.9 12.7

6 E 177 ±6 170.7 185.5 -6.3 8.5

7 E 72 ±15 55.9 66.2 -16.1 -5.8

8 E 165 ±6 166.0 174.5 1.0 9.5


SbCl5

D3h

Experimental (Å)


(Å)


(Å)

Difference (Å)

DFT– Exp.

Difference (Å)

WFT – Exp.

Sb – Claxial

2.338 2.346 2.346 0.008 0.008

Sb – Clequitorial

2.277 2.308 2.292 0.031 0.015

43

SbCl5

D3h

Computational M06-2X

(DFT) (angle º)


( angle , º)

Cl(2)-Sb(1)-Cl(3)

180.0 180.0

Cl(2)-Sb(1)-Cl(4)

90.0 90.0

Cl(2)-Sb(1)-Cl(5)

90.0 90.0

Cl(2)-Sb(1)-Cl(6)

90.0 90.0

Cl(3)-Sb(1)-Cl(4)

90.0 90.0

Cl(3)-Sb(1)-Cl(5)

90.0 90.0

Cl(3)-Sb(1)-Cl(6)

90.0 90.0

Cl(4)-Sb(1)-Cl(5)

120.0 120.0

Cl(4)-Sb(1)-Cl(6)

120.0 120.0

Cl(5)-Sb(1)-Cl(6)

120.0 120.0

44

Vibrational frequencies and structural parameters of Sb2Cl10. In the structure, antimony is purple and chorine is green.

Sb2Cl10 Mode


(DFT)

( ν /cm-1)


( ν /cm-1)

C1

1 21.4 43.12 57.6 55.13 66.6 59.34 68.1 61.65 91.0 91.26 96.1 94.87 106.8 107.18 110.0 108.09 117.3 111.4

10 128.9 129.311 143.7 144.212 152.2 151.913 155.3 152.614 165.1 164.315 173.4 169.916 176.8 175.517 180.6 176.518 193.0 190.119 212.7 206.420 224.2 219.621 233.1 234.822 250.5 253.623 332.3 324.824 333.9 326.225 369.3 359.126 377.0 366.727 378.8 368.028 386.5 376.829 388.1 379.830 399.0 389.8

45

Sb2Cl10

C1


(Å)


(Å) Cl(12)-Sb(1) 2.313 2.318Cl(11)-Sb(1) 2.314 2.319 Cl(10)-Sb(2) 2.314 2.319 Cl(9)-Sb(2) 2.313 2.318Cl(8)-Sb(2) 2.605 2.589 Cl(8)-Sb(1) 2.604 2.588Cl(7)-Sb(2) 2.323 2.329 Cl(6)-Sb(2) 2.323 2.329 Cl(5)-Sb(2) 2.604 2.588Cl(5)-Sb(1) 2.605 2.589 Cl(4)-Sb(1) 2.323 2.329 Cl(3)-Sb(1) 2.323 2.329

46

Sb2Cl10 C1


(angle, º)


(angle, º) Sb(2)-Cl(8)-Sb(1) 100.163 100.408 Sb(2)-Cl(5)-Sb(1) 100.163 100.408 Cl(6)-Sb(2)-Cl(7) 168.302 169.630 Cl(6)-Sb(2)-Cl(9) 93.699 93.287

Cl(6)-Sb(2)-Cl(10) 93.677 93.269 Cl(6)-Sb(2)-Cl(8) 85.510 86.011 Cl(6)-Sb(2)-Cl(5) 85.526 86.024 Cl(7)-Sb(2)-Cl(9) 93.699 93.290

Cl(7)-Sb(2)-Cl(10) 93.677 93.271 Cl(7)-Sb(2)-Cl(8) 85.509 86.013 Cl(7)-Sb(2)-Cl(5) 85.525 86.027

Cl(9)-Sb(2)-Cl(10) 101.716 101.457 Cl(9)-Sb(2)-Cl(8) 169.082 169.087 Cl(9)-Sb(2)-Cl(5) 89.244 89.495




Cl(11)-Sb(1)-Cl(12) 101.716 101.456 Cl(11)-Sb(1)-Cl(8) 169.039 169.049 Cl(11)-Sb(1)-Cl(5) 89.202 89.456 Cl(12)-Sb(1)-Cl(8) 89.244 89.495 Cl(12)-Sb(1)-Cl(5) 169.082 169.088 Cl(8)-Sb(1)-Cl(5) 79.837 79.592

47

Vibrational frequencies and structural parameters of ZrSbCl9. In the structure, zirconium is blue, antimony is purple and chorine is green.

ZrSbCl9 Mode


(DFT)

( ν /cm-1)


( ν /cm-1)

C1

1 34.7 41.32 59.9 64.43 63.7 65.04 67.9 79.55 73.6 79.66 94.3 96.87 98.8 98.88 109.5 108.39 116.0 109.2

10 128.3 130.011 130.9 130.212 147.7 144.813 171.5 171.214 173.7 171.615 175.1 171.816 192.9 199.317 195.7 199.618 246.0 247.619 254.6 259.320 257.4 259.521 313.9 308.122 372.6 365.823 376.5 370.824 378.3 370.825 387.1 383.826 392.8 393.427 399.4 394.3

48

ZrSbCl9

C1


(Å)


(Å) Cl(5)-Zr(1) 2.736 2.719Cl(4)-Zr(1) 2.771 2.720 Cl(3)-Zr(1) 2.766 2.718

Cl(11)-Zr(1)

2.325 2.335

Cl(10)-Zr(1)

2.325 2.335

Cl(9)-Zr(1) 2.325 2.335Cl(8)-Sb(2) 2.314 2.318 Cl(7)-Sb(2) 2.314 2.318 Cl(6)-Sb(2) 2.313 2.318Cl(5)-Sb(2) 2.492 2.476 Cl(4)-Sb(2) 2.480 2.476 Cl(3)-Sb(2) 2.484 2.477

49

ZrSbCl9 C1


(angle, º)

Computational CC2 (WFT) (angle, º)

Zr(1)-Cl(5)-Sb(2) 89.428 88.190Zr(1)-Cl(4)-Sb(2) 88.866 88.177Cl(6)-Sb(2)-Cl(7) 96.710 96.543Cl(6)-Sb(2)-Cl(8) 96.731 96.560Cl(6)-Sb(2)-Cl(4) 90.809 90.663Cl(6)-Sb(2)-Cl(3) 91.308 90.655Cl(6)-Sb(2)-Cl(5) 169.376 169.143Cl(7)-Sb(2)-Cl(8) 96.553 96.550Cl(7)-Sb(2)-Cl(4) 168.694 169.135Cl(7)-Sb(2)-Cl(3) 90.540 90.646Cl(7)-Sb(2)-Cl(5) 90.437 90.648Cl(8)-Sb(2)-Cl(4) 90.913 90.669 Cl(8)-Sb(2)-Cl(3) 168.567 169.147 Cl(8)-Sb(2)-Cl(5) 90.224 90.665 Cl(4)-Sb(2)-Cl(3) 80.826 81.120 Cl(4)-Sb(2)-Cl(5) 81.026 81.128 Cl(3)-Sb(2)-Cl(5) 80.736 81.110 Zr(1)-Cl(3)-Sb(2) 88.897 88.198 Cl(9)-Zr(1)-Cl(10) 104.057 103.042 Cl(9)-Zr(1)-Cl(11) 103.646 103.057 Cl(9)-Zr(1)-Cl(3) 88.618 90.165 Cl(9)-Zr(1)-Cl(5) 156.783 158.459 Cl(9)-Zr(1)-Cl(4) 90.517 90.152

Cl(10)-Zr(1)-Cl(11) 103.309 103.051 Cl(10)-Zr(1)-Cl(3) 156.703 158.440 Cl(10)-Zr(1)-Cl(5) 90.929 90.138 Cl(10)-Zr(1)-Cl(4) 89.083 90.135 Cl(11)-Zr(1)-Cl(3) 92.281 90.189 Cl(11)-Zr(1)-Cl(5) 89.684 90.187 Cl(11)-Zr(1)-Cl(4) 158.038 158.485 Cl(3)-Zr(1)-Cl(5) 71.700 72.650 Cl(3)-Zr(1)-Cl(4) 71.066 72.636 Cl(5)-Zr(1)-Cl(4) 71.814 72.626

50

Vibrational frequencies and structural parameters of AlCl3. In the structure, aluminum is grey and chorine is green.

Shimanouchi, T., Tables of Molecular Vibrational Frequencies Consolidated Volume II, J. Phys. Chem. Ref. Data, 1972, 6, 3, 993-1102

Hellwege, KH and AM Hellwege (ed.). Landolt-Bornstein: Group II: Atomic and Molecular Physics Volume 7: Structure Data of Free Polyatomic Molecules. Springer-Verlag. Berlin. 1976.

AlCl3 Mode Experimental

Frequency

(ν /cm-1)


( ν /cm-1)


( ν /cm-1)

∆νerror

DFT –

Exp. (cm-1)

∆νerror

WFT –

Exp. (cm-1)

D3h

1 A’1 375 ± 6 373.6 369.3 -1.4 -5.7

2 A’’2 183 ± 6 193.2 196.6 10.2 13.6

3 E’ 595 ± 6 600.5 601.0 5.5 6.0

4 E’ 150 ± 6 141.3 136.7 -8.7 -13.3


AlCl3

D3h

Experimental (Å)


(Å)


(Å)

Difference (Å)

DFT– Exp.

Difference (Å)

WFT – Exp.

Al – Cl 2.060 2.070 2.083 0.010 0.023

AlCl3

D3h



( angle , º)

Computational CC2 (WFT) ( angle , º)

Difference ( angle , º)

DFT– Exp.

Difference ( angle ,

º) WFT –

Exp. Al – Cl 120.0 120.0 120.0 0.0 0.0

51

Vibrational frequencies and structural parameters of Al2Cl6. In the structure, aluminum is grey and chorine is green.

Al2Cl6 Mode Experimental



( ν /cm-1)


( ν /cm-1)

∆νerror

DFT – Exp.

(cm-1)

∆νerror

WFT – Exp.

(cm-1)

D2h

1 B1u 33 12.5 16.7 -17.5 -16.3

2 Au 55 64.0 60.4 9.0 5.4

3 Ag 98 91.5 88.3 -6.5 -10.3

4 B3g 105 114.2 107.8 9.2 2.8

5 B2g 115 114.5 108.9 -0.5 -6.1

6 B2u 123 132.2 125.3 9.2 2.3

7 B3u 143 135.9 129.3 -7.1 -13.7

8 B1g 168 165.0 155.9 -3.0 -12.1

9 B1u 178 170.3 160.6 -7.7 -17.4

10 Ag 219 214.0 206.1 -5.0 -12.9

11 B1g 281 284.7 278.8 3.7 -2.2

12 B3u 320 322.0 308.6 2.0 -11.4

13 Ag 337 338.9 324.2 1.9 -12.8

14 B2u 418 427.0 411.9 9.0 -6.1

15 B3u 483 485.1 468.4 2.1 -14.6

16 Ag 511 524.4 507.4 13.4 -3.6

17 B2g 614 616.5 595.5 2.5 -18.5

18 B1u 626 625.4 603.8 -0.6 -22.2


52

Al2Cl6

D2h

Experimental (Å)


(Å)


(Å)

Difference (Å)

DFT– Exp.

Difference (Å)

WFT – Exp.

Al – Clterminal 2.065 2.072 2.088 0.006 0.022

Al – Clbridging 2.252 2.264 2.276 0.010 0.022

Al - Al 3.21 3.168 3.188 -0.04 -0.02

Clterminal - Clterminal 3.64 3.628 3.662 -0.01 0.02

Clbridge - Clbridge 3.16 3.234 3.250 0.07 0.09

Al2Cl6

D2h


M06-2X (DFT) ( angle , º)

CC2 (WFT) ( angle , º)


DFT– Exp.


WFT – Exp.

Al(1)-Cl(5)-Al(2)

88.807 88.899

Al(1)-Cl(4)-Al(2)

88.807 88.899

Cl(3)-Al(2)-Cl(8)

123.4 122.239 122.499 -1.2 -0.9

Cl(3)-Al(2)-Cl(5)

109.752 109.684

Cl(3)-Al(2)-Cl(4)

109.752 109.684

Cl(8)-Al(2)-Cl(5)

109.752 109.684

Cl(8)-Al(2)-Cl(4)

109.752 109.684

Cl(5)-Al(2)-Cl(4)

91.0 91.193 91.101 0.2 0.1

Cl(6)-Al(1)-Cl(7)

123.4 122.239 122.499 -1.2 -0.9

Cl(6)-Al(1)-Cl(5)

109.752 109.684

Cl(6)-Al(1)-Cl(4)

109.752 109.684

Cl(7)-Al(1)-Cl(5)

109.752 109.684

Cl(7)-Al(1)-Cl(4)

109.752 109.684

Cl(5)-Al(1)-Cl(4)

91.0 91.193 91.101 0.2 0.1

53

Hargittai, M., The molecular geometry of gas-phase metal halides. Coordination Chemistry Reviews 1988, 91, 35-88. Hellwege, KH and AM Hellwege (ed.). Landolt-Bornstein: Group II: Atomic and Molecular Physics Volume 7: Structure Data of Free Polyatomic Molecules. Springer-Verlag. Berlin. 1976.

Tomita, T.; Sjøgren, C. E.; Klaeboe, P.; Papatheodorou, G. N.; Rytter, E., High-temperature infrared and Raman spectra of aluminium chloride dimer and monomer in the vapour phase. Journal of Raman Spectroscopy 1983, 14 (6), 415-425.

Vibrational frequencies and structural parameters of NbCl5. In the structure, niobium is dark green and chorine is green.

NbCl5

D3h

Experimental (Å)


(Å)


(Å)

Difference (Å)

DFT– Exp.

Difference (Å)

WFT – Exp.

Nb – Claxial 2.338 2.324 2.329 -0.014 -0.009

Nb – Clequitorial

2.252 2.272 2.291 0.020 0.039

NbCl5 Mode

Experimental

Frequency

(ν /cm-1)


( ν /cm-1)


( ν /cm-1)

∆νerror

DFT –

Exp. (cm-1)

∆νerror

WFT –

Exp. (cm-1)

D3h

E’ 54 52.6 54.0 -1.4 0.0E’ 148 145.6 136.2 -2.4 -11.7

A2’’ 184 168.4 169.1 -15.6 -14.9

E’’ 180 178.8 172.7 -1.2 -7.3 A1

’ 317 305.2 302.7 -11.8 -14.2A1

’ 394 375.7 365.2 -18.3 -28.8 A2

’’ 396 392.0 386.5 -4.0 -9.5 E’ 430 418.4 408.1 -11.6 -21.9


54

Rosenkilde, C.; Voyiatzis, G.; Jensen, V. R.; Ystenes, M.; Oestvold, T., Raman Spectroscopic and ab initio Quantum Chemical Investigations of Molecules and Complex Ions in the Molten System CsCl-NbCl5-NbOCl3. Inorganic Chemistry 1995, 34 (17), 4360-4369. Ischenko, A. A.; Strand, T. G.; Demidov, A. V.; Spiridonov, V. P., Molecular structures, vibrational assignments and barriers to pseudorotation of gaseous niobium pentachloride and tantalum pentachloride from electron diffraction data. Journal of Molecular Structure 1978, 43 (2), 227-243.

NbCl5

D3h


(angle º)


Cl(2)-Nb(1)-Cl(3) 120.0 120.0

Cl(2)-Nb(1)-Cl(4) 90.0 90.0

Cl(2)-Nb(1)-Cl(5) 120.0 120.0

Cl(2)-Nb(1)-Cl(6) 90.0 90.0

Cl(3)-Nb(1)-Cl(4) 90.0 90.0

Cl(3)-Nb(1)-Cl(5) 120.0 120.0

Cl(3)-Nb(1)-Cl(6) 90.0 90.0

Cl(4)-Nb(1)-Cl(5) 90.0 90.0

Cl(4)-Nb(1)-Cl(6) 180.0 180.0

Cl(5)-Nb(1)-Cl(6) 90.0 90.0

55

Vibrational frequencies and structural parameters of Nb2Cl10. In the structure, niobium is dark green and chorine is green.

Nb2Cl10 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

C1

1 44.0 46.42 57.5 49.73 61.1 50.34 63.0 53.15 78.1 93.36 97.3 95.67 103.8 97.08 106.9 100.39 120.8 115.3

10 123.8 115.411 135.2 125.112 152.6 143.013 154.3 147.614 165.6 157.315 168.7 161.216 172.4 162.517 185.0 176.618 196.9 187.719 212.2 216.720 219.8 227.721 238.7 250.322 245.4 252.623 354.4 338.724 355.5 339.525 367.6 371.326 405.4 374.327 406.1 383.828 406.7 384.629 418.3 400.830 427.2 403.2

56

Nb2Cl10

C1


(Å)


(Å) Nb(1)-Cl(5)

2.605 2.577

Nb(2)-Cl(5)

2.604 2.577

Cl(8)-Nb(1)

2.604 2.577

Cl(8)-Nb(2)

2.605 2.577

Cl(12)-Nb(1)

2.259 2.284

Cl(11)-Nb(1)

2.259 2.284

Cl(10)-Nb(2)

2.259 2.284

Cl(9)-Nb(2)

2.259 2.284

Cl(7)-Nb(2)

2.307 2.320

Cl(6)-Nb(2)

2.307 2.320

Cl(4)-Nb(1)

2.307 2.320

Cl(3)-Nb(1)

2.307 2.320

57

Nb2Cl10 C1


(angle, º)

Computational CC2 (WFT) (angle, º)

Nb(1)-Cl(5)-Nb(2) 101.556 101.311 Cl(6)-Nb(2)-Cl(7) 165.193 167.517 Cl(6)-Nb(2)-Cl(9) 94.598 93.906 Cl(6)-Nb(2)-Cl(10) 94.577 93.895 Cl(6)-Nb(2)-Cl(8) 84.262 85.175 Cl(6)-Nb(2)-Cl(5) 84.281 85.181 Cl(7)-Nb(2)-Cl(9) 94.598 93.906 Cl(7)-Nb(2)-Cl(10) 94.574 93.894 Cl(7)-Nb(2)-Cl(8) 84.266 85.172 Cl(7)-Nb(2)-Cl(5) 84.274 85.179 Cl(9)-Nb(2)-Cl(10) 103.280 102.539 Cl(9)-Nb(2)-Cl(8) 167.609 168.091 Cl(9)-Nb(2)-Cl(5) 89.167 89.403 Cl(10)-Nb(2)-Cl(8) 89.110 89.369 Cl(10)-Nb(2)-Cl(5) 167.552 168.057 Cl(8)-Nb(2)-Cl(5) 78.442 78.688 Nb(2)-Cl(8)-Nb(1) 101.556 101.311 Cl(3)-Nb(1)-Cl(4) 165.199 167.519 Cl(3)-Nb(1)-Cl(11) 94.575 93.895 Cl(3)-Nb(1)-Cl(12) 94.596 93.906 Cl(3)-Nb(1)-Cl(5) 84.264 85.176 Cl(3)-Nb(1)-Cl(8) 84.284 85.182 Cl(4)-Nb(1)-Cl(11) 94.572 93.894 Cl(4)-Nb(1)-Cl(12) 94.597 93.905 Cl(4)-Nb(1)-Cl(5) 84.268 85.173 Cl(4)-Nb(1)-Cl(8) 84.277 85.179

Cl(11)-Nb(1)-Cl(12) 103.279 102.539 Cl(11)-Nb(1)-Cl(5) 89.111 89.368 Cl(11)-Nb(1)-Cl(8) 167.556 168.057 Cl(12)-Nb(1)-Cl(5) 167.610 168.093 Cl(12)-Nb(1)-Cl(8) 89.165 89.404 Cl(5)-Nb(1)-Cl(8) 78.445 78.689

58

Vibrational frequencies and structural parameters of FeCl3. In the structure, iron is orange and chorine is green.

FeCl3 Mode Experimental

Frequency

(ν /cm-1)


( ν /cm-1)


( ν /cm-1)

∆νerror

DFT –

Exp. (cm-1)

∆νerror

WFT –

Exp. (cm-1)

D3h

1 A’’2 116.0 107.15 79.21 -8.85 -36.79

2 E’ 102.0 111.92 97.41 9.92 -4.59

3 A’1 367.0 372.88 354.14 5.88 -12.86

4 E’ 464.8 475.51 469.73 10.71 4.93


59

Varga, Z.; Kolonits, M.; Hargittai, M., Gas-phase structures of iron trihalides: a computational study of all iron trihalides and an electron diffraction study of iron trichloride.(Report). Inorganic Chemistry 2010, 49 (3), 1039-1045. Givan, A.; Loewenschuss, A., Matrix isolation Raman spectra of FeCl3 and Fe2Cl6. Journal of Raman Spectroscopy 1977, 6 (2), 84-88.

Vibrational frequencies and structural parameters of Fe2Cl6. In the structure, iron is orange and chorine is green.

FeCl3

D3h

Experimental (Å)


(Å)


(Å)

Difference (Å)

DFT– Exp.

Difference (Å)

WFT – Exp.

Fe – Cl 2.136 2.156 2.132 0.020 -0.004

FeCl3

D3h



( angle , º)



DFT– Exp.


º) WFT –

Exp. Fe – Cl 116.6 120.0 120.0 3.4 3.4

60

Fe2Cl6 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

C1

1 32.1 14.12 58.6 52.73 80.3 68.04 84.8 72.25 87.8 74.36 109.3 91.87 110.3 95.38 119.9 101.49 139.9 111.310 158.8 133.111 239.0 226.212 287.7 254.713 312.8 294.714 330.9 318.715 405.9 385.116 427.3 398.717 465.6 433.718 472.2 437.1

Fe2Cl6

C1


(Å)


(Å) Cl(8)-Fe(2) 2.154 2.134Cl(7)-Fe(1) 2.154 2.136 Cl(6)-Fe(1) 2.154 2.134 Cl(5)-Fe(2) 2.374 2.324Cl(5)-Fe(1) 2.374 2.324 Cl(4)-Fe(2) 2.374 2.324Cl(4)-Fe(1) 2.374 2.324 Cl(3)-Fe(2) 2.154 2.136

61

Fe2Cl6

C1


(angle, º)


(angle, º) Fe(2)-Cl(5)-Fe(1) 88.404 83.038 Fe(2)-Cl(4)-Fe(1) 88.404 83.038 Cl(3)-Fe(2)-Cl(8) 118.846 113.753 Cl(3)-Fe(2)-Cl(5) 110.277 110.732 Cl(3)-Fe(2)-Cl(4) 110.277 110.731 Cl(8)-Fe(2)-Cl(5) 111.689 112.660 Cl(8)-Fe(2)-Cl(4) 111.689 112.658 Cl(5)-Fe(2)-Cl(4) 90.501 94.834 Cl(6)-Fe(1)-Cl(7) 118.846 113.754 Cl(6)-Fe(1)-Cl(5) 111.689 112.660 Cl(6)-Fe(1)-Cl(4) 111.689 112.657 Cl(7)-Fe(1)-Cl(5) 110.277 110.732 Cl(7)-Fe(1)-Cl(4) 110.277 110.730 Cl(5)-Fe(1)-Cl(4) 90.501 94.834

62

Vibrational frequencies and structural parameters of ZrFeCl7 (triple chloride bridge). In the structure, zirconium is blue, iron is orange and chorine is green.

ZrFeCl7 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

Three Chloride Bridge

C1

1 51.7 54.42 61.0 60.03 64.0 60.64 74.6 77.75 77.7 78.66 109.6 106.27 114.4 111.08 116.4 111.39 135.2 138.210 139.7 138.511 153.6 153.912 157.4 154.113 164.7 159.614 216.5 215.815 327.1 329.316 335.2 339.317 340.0 339.518 385.9 382.119 393.3 394.820 396.3 395.021 476.0 462.1

63

ZrFeCl7

3 Clbridge C1


(Å)


(Å) Cl(3)-Zr(1) 2.803 2.758 Cl(6)-Zr(1) 2.801 2.759 Cl(5)-Zr(1) 2.783 2.757 Cl(9)-Zr(1) 2.323 2.333 Cl(8)-Zr(1) 2.322 2.333 Cl(7)-Fe(2) 2.145 2.130 Cl(6)-Fe(2) 2.280 2.260 Cl(5)-Fe(2) 2.286 2.261 Cl(4)-Zr(1) 2.324 2.333 Cl(3)-Fe(2) 2.282 2.260

64

ZrFeCl7

3 Clbridge C1


(angle, º)


(angle, º) Zr(1)-Cl(6)-Fe(2) 79.222 78.212Zr(1)-Cl(3)-Fe(2) 79.132 78.218Cl(7)-Fe(2)-Cl(3) 123.039 122.164Cl(7)-Fe(2)-Cl(5) 122.576 122.148Cl(7)-Fe(2)-Cl(6) 122.445 122.175Cl(3)-Fe(2)-Cl(5) 93.280 94.287Cl(3)-Fe(2)-Cl(6) 93.795 94.317Cl(5)-Fe(2)-Cl(6) 93.679 94.292Zr(1)-Cl(5)-Fe(2) 79.506 78.240Cl(4)-Zr(1)-Cl(8) 103.563 102.877Cl(4)-Zr(1)-Cl(9) 103.298 102.887Cl(4)-Zr(1)-Cl(5) 89.452 89.810 Cl(4)-Zr(1)-Cl(6) 159.017 159.415 Cl(4)-Zr(1)-Cl(3) 90.967 89.798 Cl(8)-Zr(1)-Cl(9) 103.958 102.876 Cl(8)-Zr(1)-Cl(5) 157.496 159.365 Cl(8)-Zr(1)-Cl(6) 89.642 89.756 Cl(8)-Zr(1)-Cl(3) 88.350 89.758 Cl(9)-Zr(1)-Cl(5) 90.480 89.798 Cl(9)-Zr(1)-Cl(6) 88.906 89.783 Cl(9)-Zr(1)-Cl(3) 158.134 159.401 Cl(5)-Zr(1)-Cl(6) 73.222 73.874 Cl(5)-Zr(1)-Cl(3) 72.935 73.878 Cl(6)-Zr(1)-Cl(3) 72.932 73.866

65

Vibrational frequencies and structural parameters of ZrFeCl7 (double chloride bridge). In the structure, zirconium is blue, iron is orange and chorine is green.

66

ZrFeCl7 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

Two Chloride Bridge

C1

1 18.5 12.5 2 32.6 22.3 3 69.5 64.9 4 76.9 74.6 5 85.5 81.7 6 87.4 87.8 7 99.8 89.9 8 115.6 110.3 9 116.8 117.4

10 130.6 124.2 11 135.3 125.2 12 156.5 144.9 13 196.5 202.4 14 261.7 267.8 15 299.3 294.3 16 318.7 310.2 17 384.3 380.8 18 388.3 392.3 19 411.8 405.1 20 419.2 410.0 21 462.2 449.1

ZrFeCl7

2 Clbridge C1


(Å)


(Å) Cl(9)-Fe(2) 2.158 2.145Cl(8)-Zr(1) 2.328 2.340 Cl(7)-Fe(2) 2.160 2.145 Cl(6)-Zr(1) 2.333 2.325Cl(5)-Fe(2) 2.359 2.301 Cl(5)-Zr(1) 2.623 2.661Cl(4)-Zr(1) 2.304 2.327 Cl(3)-Fe(2) 2.343 2.347 Cl(3)-Zr(1) 2.653 2.568

67

ZrFeCl7

2 Clbridge C1


(angle, º)


(angle, º) Fe(2)-Cl(5)-Zr(1) 95.824 95.187 Fe(2)-Cl(3)-Zr(1) 95.405 96.577 Cl(7)-Fe(2)-Cl(9) 118.576 118.278 Cl(7)-Fe(2)-Cl(5) 109.982 112.350 Cl(7)-Fe(2)-Cl(3) 111.191 110.153 Cl(9)-Fe(2)-Cl(5) 112.249 112.286 Cl(9)-Fe(2)-Cl(3) 112.536 110.044 Cl(5)-Fe(2)-Cl(3) 88.308 90.182 Cl(4)-Zr(1)-Cl(6) 105.224 111.280 Cl(4)-Zr(1)-Cl(8) 108.438 99.816 Cl(4)-Zr(1)-Cl(5) 106.593 88.465 Cl(4)-Zr(1)-Cl(3) 97.964 124.809 Cl(6)-Zr(1)-Cl(8) 98.835 100.416 Cl(6)-Zr(1)-Cl(5) 84.826 89.541 Cl(6)-Zr(1)-Cl(3) 153.725 121.668 Cl(8)-Zr(1)-Cl(5) 142.343 163.604 Cl(8)-Zr(1)-Cl(3) 85.123 85.665 Cl(5)-Zr(1)-Cl(3) 76.748 78.006

68

Vibrational frequencies and structural parameters of NbOCl3. In the structure, niobium is dark green, oxygen is red and chorine is green.

Giricheva, N. I.; Girichev, G. V., Molecular structure of niobium tetra- and oxytrihalides. Journal of Molecular Structure 1999, 484 (1), 1-9.

NbOCl3

C3v



( angle , º)



DFT– Exp.


º) WFT –

Exp. O = Nb -

Cl 107.5 106.8 105.5 -0.7 -2.0

Cl – Nb - Cl

111.3 112.1 113.1 0.8 1.8

NbOCl3

C3v

Experimental (Å)


(Å)


(Å)

Difference (Å)

DFT– Exp.

Difference (Å)

WFT – Exp.

Nb – Cl 2.276 2.285 2.301 0.009 0.025

Nb = O 1.682 1.664 1.755 -0.018 0.073

69

NbOCl3 Mode Exp.



( ν /cm-1)


( ν /cm-1)

∆νerror

DFT –

Exp. (cm-1)

∆νerror

WFT –

Exp. (cm-1)

C3v

E 106 108.5 96.6 2.5 -9.4A1 133 131.3 117.4 -1.7 -15.6 E 225 236.4 196.3 11.4 -28.7 A1 395 389.7 369.4 -5.3 -25.6E 448 435.2 422.5 -12.8 -25.5 A1 997 1078.7 730.8 81.7 -266.2


70

Vibrational frequencies and structural parameters of Nb2O2Cl6. In the structure, niobium is dark green, oxygen is red and chorine is green.

71

Nb2O2Cl6

C1


(Å)


(Å) O(5)-Nb(7) 2.292 2.458

O(4)-Nb(1) 2.292 2.458

Cl(10)-Nb(7) 2.290 2.306

Cl(9)-Nb(7) 2.290 2.306

Cl(8)-Nb(7) 2.280 2.286

Nb(7)-O(4) 1.736 1.774

Cl(6)-Nb(1) 2.280 2.286

O(5)-Nb(1) 1.736 1.774

Cl(3)-Nb(1) 2.290 2.306

Cl(2)-Nb(1) 2.290 2.306

Nb2O2Cl6 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

C1

1 49.7 31.62 58.9 47.63 67.0 48.64 75.6 54.45 105.8 70.76 115.5 102.97 127.9 107.78 129.2 111.89 131.8 115.3

10 146.4 124.911 155.7 132.212 179.5 145.213 219.6 203.414 296.1 218.615 300.8 244.716 382.3 328.517 394.9 370.818 399.1 373.419 417.9 402.220 428.0 408.321 448.5 417.722 471.1 429.123 890.3 758.924 942.9 762.8

72

Nb2O2Cl6

C1


(angle, º)


(angle, º) Nb(7)-O(5)-Nb(1) 104.910 105.086

Cl(8)-Nb(7)-Cl(9) 98.071 101.594

Cl(8)-Nb(7)-Cl(10) 98.033 101.593

Cl(8)-Nb(7)-O(5) 177.448 177.909

Cl(8)-Nb(7)-O(4) 102.358 102.994

Cl(9)-Nb(7)-Cl(10) 124.383 125.948

Cl(9)-Nb(7)-O(5) 83.127 79.283

Cl(9)-Nb(7)-O(4) 113.843 110.604

Cl(10)-Nb(7)-O(5) 83.075 79.283

Cl(10)-Nb(7)-O(4) 113.903 110.604

O(5)-Nb(7)-O(4) 75.090 74.914

Nb(7)-O(4)-Nb(1) 104.910 105.086

Cl(2)-Nb(1)-Cl(3) 124.382 125.948

Cl(2)-Nb(1)-Cl(6) 98.033 101.593

Cl(2)-Nb(1)-O(5) 113.903 110.605

Cl(2)-Nb(1)-O(4) 83.076 79.283

Cl(3)-Nb(1)-Cl(6) 98.070 101.594

Cl(3)-Nb(1)-O(5) 113.844 110.604

Cl(3)-Nb(1)-O(4) 83.127 79.283

Cl(6)-Nb(1)-O(5) 102.358 102.994

Cl(6)-Nb(1)-O(4) 177.448 177.908

O(5)-Nb(1)-O(4) 75.090 74.914

73

Vibrational frequencies and structural parameters of ZrNbOCl7. In the structure, zirconium is blue, niobium is dark green, oxygen is red and chorine is green.

74

ZrNbOCl7 Mode Computational M06-2X (DFT)

( ν /cm-1)


( ν /cm-1)

C1

1 18.6 6.62 26.4 24.73 51.6 40.14 75.6 74.95 85.0 81.46 85.7 84.57 99.7 97.68 115.5 106.59 119.3 113.3

10 134.5 125.411 142.3 132.412 155.4 147.613 225.7 198.014 233.0 202.015 236.7 235.416 255.5 239.317 285.0 289.618 298.5 294.019 391.9 378.120 394.7 381.821 404.9 391.822 414.0 400.223 416.8 411.024 1097.2 699.7

ZrNbOCl7

C1


(Å)


(Å) Nb(10)-Cl(2) 2.563 2.551

Nb(10)-Cl(3) 2.563 2.551

Nb(10)-Cl(5) 2.298 2.311

Nb(10)-O(1) 1.656 1.759

Nb(10)-Cl(4) 2.298 2.311

Cl(9)-Zr(6) 2.332 2.343

Cl(8)-Zr(6) 2.332 2.343

Cl(7)-Zr(6) 2.307 2.318

Zr(6)-Cl(2) 2.616 2.582

Zr(6)-Cl(3) 2.615 2.581

75

ZrNbOCl7

C1


(angle, º)


(angle, º) Cl(4)-Nb(10)-O(1) 104.994 103.765 Cl(4)-Nb(10)-Cl(5) 99.793 100.717 Cl(4)-Nb(10)-Cl(2) 150.815 152.578 Cl(4)-Nb(10)-Cl(3) 86.230 86.511 O(1)-Nb(10)-Cl(5) 104.993 103.763 O(1)-Nb(10)-Cl(2) 100.848 100.028 O(1)-Nb(10)-Cl(3) 100.849 100.009 Cl(5)-Nb(10)-Cl(2) 86.233 86.516 Cl(5)-Nb(10)-Cl(3) 150.817 152.600 Cl(2)-Nb(10)-Cl(3) 75.712 76.034 Cl(7)-Zr(6)-Cl(8) 107.245 107.362 Cl(7)-Zr(6)-Cl(9) 107.237 107.343 Cl(7)-Zr(6)-Cl(2) 103.726 101.930 Cl(7)-Zr(6)-Cl(3) 103.740 101.978 Cl(8)-Zr(6)-Cl(9) 98.813 98.131 Cl(8)-Zr(6)-Cl(2) 85.122 85.716 Cl(8)-Zr(6)-Cl(3) 145.901 147.623

Cl(9)-Zr(6)-Cl(2) 145.923 147.687

Cl(9)-Zr(6)-Cl(3) 85.124 85.715

Cl(2)-Zr(6)-Cl(3) 73.927 74.977

Nb(10)-Cl(3)-Zr(6) 101.320 99.492

Nb(10)-Cl(2)-Zr(6) 101.320 99.491

Purification of Zirconium Tetrachloride from UNF Cladding Reports/FY 2015/15... · 2019-01-03 ·...

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