Atomic structure at the nanoscale: a 21 st century materials challenge 25 September 2009 Emil S....
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Transcript of Atomic structure at the nanoscale: a 21 st century materials challenge 25 September 2009 Emil S....
Atomic structure at the nanoscale: a 21st century materials challenge
25 September 2009
Emil S. Bozin
Applied Physics and Applied Mathematics Department, Columbia UniversityCondensed Matter Physics and Material Science Department, BNL
Workshop on Characterization of Advanced Materials under Extreme Environments for Next Generation Energy Systems
September 25-26, 2009
Pb (s.g. Fm-3m)
3.479
4.920
6.026
6.958
Complex nanostructured materials
Images: Igor Levin/Tom Pinnavaia/Sandra Rosenthal
Nanoporous (mesoporous) materials
NanoparticlesNanostructured bulk crystals
INT
RO
- Complex bulk systems with interesting physical properties are often inhomogeneous on a nanometer lengthscale
high-temperature superconductors, colossal magnetoresistive materials,
high performance thermoelectric materials …
- Nano-particles, nano-tubes, nano-wires etc. important for applications optoelectronics, nanosensors, programmed release drug delivery systems…
Physical properties often critically depend on the nano-scale structure, rather than the long-range structure!
Crystallography gives average structureR
OU
TIN
E
Figures: J.S.O. Evans et al.
and M. Tucker et al.
Bragg peak info ONLY
Rietveld method
in powders
Example: Ho2(Ti2‑xHox)O7-x/2 ”stuffed spin ice” 300K neutron diffraction patterns (GPPD, IPNS, Argonne)
x=0.00x=0.30x=0.50x=0.67
pyrochlore fluorite
x=0.3
Crystallography challenged: materials w/ disorderC
HA
LLE
NG
E
Rietveld approach assumption: crystals are perfectly periodic…
…but this is not always the case!
Crystallography challenged: nano-crystalsC
HA
LLE
NG
E
Figures: J.S.O. Evans et al.
and M. Tucker et al.
Bragg peak info ONLY
Rietveld method
in powders
Global ApproachF
UT
UR
E
• Add complementary information– Extra experimental data– Theoretical constraints
Science, 316, 561 (2007).
What is PDF?
5.11Å4.92Å
4.26Å
3.76Å
2.84Å
2.46Å
1.42Å
Pair distribution function (PDF) gives the probability of finding an atom at a distance “r” from a given atom.
AP
PR
OA
CH
Pair Distribution Function Method: Applicability
- Originally: short range order in liquids and glasses
- Since late 1980’s: disorder in crystalline materials
- Recently: nanocrystalline materials
Lanthanum Aluminate glass
J. Du and L.R. Corales, J. Non-Cryst. Solids (2007)
AP
PR
OA
CH
Th. Proffen et al, Los Alamos Science (2006)
Gold: bulk vs nanoparticle
Raw data
Structure function
QrdQQSQrG sin]1)([2
)(0
Pair Distribution Function from total scattering experimentsA
PP
RO
AC
H
Bragg intensity → long range order
Diffuse intensity →short range order
How can we get short range structural information?
0
)sin(]1)([2
)( dQQrQSQrG
Pair Distribution Function from total scattering experimentsA
PP
RO
AC
H
short range informationintermediate range information
Strength of the Pair Distribution Function
Pair Distribution Function: info on different lengthscalesA
PP
RO
AC
H
Rapid Acquisition PDF (RAPDF) at a synchrotoron: Measuring PDFs in a few seconds
P. Chupas et al, J. Appl. Cryst. 36, 1342-1347 (2003).
Pair Distribution Function: rapid data collection modeA
PP
RO
AC
H
Time-resolved PDF measurements:
Reduction of PtIV Pt0
P. Chupas et al, J. Appl. Cryst. 40, 463-470 (2007).
Application of a large-area, high-sensitivity, fast readout, flat-panel GE detector based on an amorphous silicon
Nickel data, 0.03s collection time, Qmax 28 Å-1
Pair Distribution Function: rapid data collection modeA
PP
RO
AC
H
Ni300K Ni data from GPPD at IPNS, ANL
data
difference
model
PDF Programs
PDFgetX1
PDFgetN1
PDFgui2 (PDFfit)1 http://nirt.pa.msu.edu2 http://www.diffpy.org/
Pair Distribution Function: modelingA
PP
RO
AC
H
Nanometer scale structure of CuIr2S4
Local structural aspects of the metal-insulator transition
in CuIr2S4
- X-ray total scattering study -
Collaboration with: J.F. Mitchell, MSD, Argonne Nat. Lab.
Credits: Y.S. Hor, A.S. Masadeh, H.J. Kim, P. Juhas, S.J.L. Billinge
HIG
HLI
GH
T
HIG
HLI
GH
T
The role of lattice geometry – frustrationSpinel structure: AB2X4
Crystallizes in the cubic (isometric) crystal system
B-sublattice – pyrochlore – corner-shared tetrahedra
This sublattice promotes frustration, interesting physics arises in spin (AF
interactions) and charge (half-integer valence) sectors!
MgAl2O4
X sitesB octahedral sites
A tetrahedral sites
Thiospinel CuIr2S4 properties: structural transition
- in-situ TEM micrographs
W. Sun et al., J. Phys.l Soc. Jpn., 70, 2817 (2001).
- Electron diffraction
- TS226K
Tetragonal I41/amd
Cubic Fd-3m
HIG
HLI
GH
T
Thiospinel CuIr2S4 properties
- Metallic at high T- Insulating at low T
- TMI226K
PES, NMR, LDA:
Cu1+ Ir3.5+ (half-integer!)
PES of the insulating phase:
~0.1 eV gap near EF
Ir 5d DOS strongly distorted
T. Furubayashi et al., Solid State Comm. 126, 617 (2003).
S. Nagata et al., Physica B. 194, 1077 (1994).
J. Matsuno et al., Phys. Rev. B. 55, R15979 (1997).
HIG
HLI
GH
T
Thiospinel CuIr2S4 properties
- High T: Pauli paramagnetic- Low T: nonmagnetic
(NMR, Mössbauer, magnetic susceptibility)
T. Furuyabashi et al., J. Phys. Soc. Japan. 63, 3333 (1994).
Ir8S24 octamer
HIG
HLI
GH
T
CuIr2S4: background information
D.I. Khomskii and T. Mizokawa,
PRL 94, 156402 (2005).
Low-T structureRed octahedra Ir3+
Blue octahedra Ir4+
P.G. Radaelli et al.,
Nature 416, 155 (2002).
- Metal at high temperature (Ir is nominally 3.5+)- Insulator at low temperature (Ir’s are 3+ AND 4+)
- T-induced Metal-Insulator transition at ~226K
- Charge ordering and spin dimerization at low-T - Long range charge ordered patterns of isomorphic
octamers- Associated structural change (Peierls distortion)- Ir4+: short Ir-Ir distances appear (~3.0Å) - DIMER- Ir3+: no short Ir-Ir distances (~3.5Å)
HIG
HLI
GH
T
Reduced dimensionality due to specifics of xy-orbitals
CuIr2S4
D.I. Khomskii, Physica Scripta 72, CC8-14 (2005)
HIG
HLI
GH
T
CuIr2S4: effect of x-ray irradiation
V. Kiryukhin et al.,
PRL 97, 225503 (2006).
Cubic Fd-3m
Triclinic P-1
Tetragonal I41/amd
Long range ordered dimersIC C
Insulator Metal
Tetragonal I41/amd
- Incommensurate (IC) short range state below ~40K
- Commensurate (C) short range state 40K<T<~100K
Melting of LRO dimers at low T!
HIG
HLI
GH
T
CuIr2S4: effect of x-ray irradiation
T. Furubayashi et al., Solid State Comm. 126, 617 (2003).
V. Kiryukhin et al.,
PRL 97, 225503 (2006).
Cubic Fd-3m
Triclinic P-1
Tetragonal I41/amd
Long range ordered dimers
When x-ray irradiatedno long range ordered
dimersIC C
Insulator Metal
- Incommensurate (IC) short range state below ~40K
- Commensurate (C) short range state 40K<T<~100K
HIG
HLI
GH
T
CuIr2S4: local structure view of Metal-Insulator transition
Issues:Do the dimers survive locally when the
long range order is removed by:
(1) temperature(2) Cr-doping (3) x-ray irradiation
Total Scattering Approach:• Crystallography – sensitive
to long range ordered dimers• Atomic PDF – sensitive to
presence of dimers
Cubic Fd-3m
Triclinic P-1
Tetragonal I41/amd
Long range ordereddimers
no long range ordereddimers
IC C
Insulator Metal
HIG
HLI
GH
T
CuIr2S4: T-driven Metal-Insulator transition
30s
Dramatic changes observed in the local structure, consistent with crystallography (T=10K)R. Endoh et al.,
PRB 68, 115106 (2003).
Compare the case where the MI
transition is not crossed! (T=10K)
HIG
HLI
GH
T
Structure of LaMnO3 across the JT-transition at 720 K
30s
Distortions persist locally!
700 K data (blue) vs 750 K data (red)
LaMnO3: utilizing intuitiveness of PDF - simplicity
HIG
HLI
GH
T
CuIr2S4: T-driven Metal-Insulator transition
30s
Dramatic changes observed in the local structure, consistent with crystallography (T=10K)R. Endoh et al.,
PRB 68, 115106 (2003).
Compare the case where the MI
transition is not crossed! (T=10K)
HIG
HLI
GH
T
CuIr2S4: Hysteretic structural behavior observed
Phase 2: Triclinic P-1 @180 K
Phase 1: Cubic Fd-3m @230 K
Fraction of dimerized sample from 2-phase fit
R. Endoh et al.,
PRB 68, 115106 (2003).HIG
HLI
GH
T
CuIr2S4: Cr-doping driven Metal-Insulator transition (5% Cr-doping)
30s
Dimers disappear locally when Insulator-Metal transition is invoked by Cr-doping at 200K
R. Endoh et al.,
PRB 68, 115106 (2003).
HIG
HLI
GH
T
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays
0.5s 1s
30s0.5s
MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s
HIG
HLI
GH
T
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays
0.5s 1s
30s0.5s
MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s
HIG
HLI
GH
T
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays
0.5s 1s
30s0.5s
MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s
HIG
HLI
GH
T
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays
0.5s 1s
30s0.5s
MAR345 exposures: 0.5s, 1s, 30s, ~2 minute break in exposing, 0.5s
HIG
HLI
GH
T
30s0.5s
Melting observed in present study is approximately order of magnitude “faster” than that in the earlier reports
H. Ishibashi et al., PRB 66, 144424 (2002).
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays
HIG
HLI
GH
T
15s
30s0.5s
Cumulative
Data
Collection
exposure
collection
Continuous
Exposure
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays – local aspects
HIG
HLI
GH
T
15s
30s0.5s
Collection: 250 msec snapshot
Exposure: continuous 23 sec
Snapshot
Data
Collection
exposure
collection
23 sec
Differences due to statistics only,
the underlying local structures are the same!
CuIr2S4: Melting the long range ordered dimerization pattern by x-rays – local aspects
HIG
HLI
GH
T
Diffraction
patterns
(long range order)
profiles
(short range order)
Temperature Doping Irradiation
CuIr2S4: Melting the long range ordered dimerization pattern – overview
HIG
HLI
GH
T
CuIr2S4 thiospinel: Summary
Do the dimers survive locally when the long range order is removed by:
1. Temperature: NO: the local dimers are destroyed Fraction of the sample that is dimerized has been mapped out through the
hysteretic phase transition2. Cr-doping: NO: the local dimers are destroyed3. x-ray irradiation: YES: the local dimers survive
98keV x-rays also melt the long range order but the melting is faster than previous reportsLong range order recovers quickly at 100K as previously observed
Total Scattering Approach:• Crystallography – sensitive to long range order dimers• Atomic PDF – sensitive to presence of dimers• Dimer peaks clearly resolved and visible
HIG
HLI
GH
T
Acknowledgements• People:Simon Billinge
(Columbia/BNL)
Adam DeConinck (MSU)
Pavol Juhas (Columbia)
Xiangyun Qiu (MSU, now at NIH)
Marek Schmidt (MSU/ISIS, now at Polish Academy of Sciences)
Hyunjeong Kim (LANSCE)
Ahmad Masadeh (MSU, now at University of Jordan)
Gianluca Paglia (MSU, now in industry, Australia)
Thomas Proffen (LANSCE, Los Alamos)
John Mitchell (MSD, Argonne)
Tapan Chatterji (ILL, Grenoble, FR)
Paolo Radaelli (ISIS, UK)
Peter Chupas, Douglas Robinson (APS, Argonne)
• Facilities:Advanced Photon Source, ArgonneIntense Pulsed Neutron Source, ArgonneLos Alamos Neutron Scattering CenterISIS, Rutherford Appleton Laboratory
• Funding: NSF DMR 0304349, DOE DE-AC02-06CH11375, DOE DE-AC52-06NA25396, DOE DE-AC02-98CH10886.