Bill David, ISIS Facility, Rutherford Appleton Laboratory, UK & Inorganic Chemistry Laboratory, University of Oxford, UK

Combined computational and neutron powder diffraction studies of disordered hydride structures

RAL: ISIS & Diamond

ISIS TSII Oxford Chemistry Oxford

95A

Real Crystallography of Real Materials under Real Conditions Real Crystallography of Real Materials under Real Conditions

superhard graphite pencil “lead” proteins in operando

C60 pharmaceuticals turbine blades nanomaterials

lithium batteries hydrogen stores fuel cells CO2 sequestration

tensile stress paracetamol novel techniques microstructure

2016 | The centenary of powder diffraction

ECN Petten, Netherlands (1966)

Neutron powder diffraction

“A structure refinement method is described which does not use integrated neutron powder intensities, single or overlapping, but employs directly the profile intensities obtained from step-scanning measurements of the powder diagram. Nuclear as well as magnetic structures can be refined, the latter only when their magnetic unit cell is equal to, or a multiple of, the nuclear cell. The least-squares refinement procedure allows, with a simple code, the introduction of linear or quadratic constraints between the parameters.”

Hugo Rietveld

The Rietveld Method

Rietveld refinement

The Rietveld Method

R 2016 | The semicentenary of the Rietveld Method

2016 | The centenary of powder diffraction

quinquagenary

golden jubilee

LiBH4

LiNH2 / Li2NH

mobility

topology

non-stoichiometry

Li4BN3H10

Hd+-Hd-

H2 ↑

Li2BNH6

Hd+-Hd-

(H2 ↑ liquid)

ammonia stores LiBH4 Li(NH3)BH4

superionic

NH3BH3

NH4BH4

Hd+-Hd-

dihydrogen

bonding

Li(NH3)4 expanded metal

LiBH4 ↔ Li(NH3)BH4 ↔ Li(NH3)2BH4 ↔ Li(NH3)3BH4 ↔ Li(NH3)4BH4

LiNH2BH3

one-shot hydrogen stores

complex molecular anions

7Li11BD4 : order and disorder 7Li11BD4 : order and disorder

ISIS

LiBD4 : a superionic conductor LiBD4 : a superionic conductor

Matsuo et al., Appl. Phys. Lett. 91, 224103 (2007) Refined HT crystal structure (perhaps there is disorder!)

HT-LiBH4 | space group P63mc

LiBD4 : a superionic conductor LiBD4 : a superionic conductor

Refined HT crystal structure (perhaps there is disorder!)

HT-LiBH4 | space group P63mc ZnS | wurtzite | space group P63mc

LiBH4 : a PDF study of disorder LiBH4 : a PDF study of disorder 7Li11BD4 : GEM (ISIS)

B-D 1.21Å

D-D 1.95Å

B-D 1.22Å

D-D 1.97Å

LT-LiBH4 : powder diffraction – a conundrum LT-LiBH4 : powder diffraction – a conundrum

110.1o 111.2o

108.6o 107.1o

LiBD4 | space group Pnma

HT-LiBD4 HT-LiBD4

HT-LiBH4 | space group P63mc

Refined HT crystal structure (wurtzite analogue is not the place to start)

HT-LiBH4 | space group P63/mmc

ADPs (10% probability)

HT-LiBH4 : introducing golf balls HT-LiBH4 : introducing golf balls

q

f

prm Occ_H1_010_030 = avo*(Y00 + C20*Y20_010_030 + C33*Y33_010_030 + C40*Y40_010_030 + C53*Y53_010_030 ; : 0.02347`_0.00012

prm !Y53_010_030 = -0.4892383*(9*Cos(0.017453*060)^2-1) *Sin(0.017453*060)^3*Cos(3*0.017453*010); : -0.34400

Y53 = -0.4892383*(9cos(th)^2-1 )*sin(th)^3 cos(3ph)

prm !avo 0.038955 prm C20 -0.03219`_0.00409 prm C33 0.55600`_0.00212 prm C40 -0.27161`_0.00508 prm C53 -0.11408`_0.00696

occ = 0.010989 = 2/182 = Y00*avo = 0.2820947918*avo ; avo =0.010989/0.2820947918 = 0.038955

HT-LiBH4: the golf ball – 37 symmetry-independent “atomlets” HT-LiBH4: the golf ball – 37 symmetry-independent “atomlets”

20

LiBH4: ADPs LiBH4: ADPs

ADPs = anisotropic displacement parameters (10% probabilities)

ADPs

Li

B

21

LiBH4: ADPs – DFT molecular dynamics + diffraction LiBH4: ADPs – DFT molecular dynamics + diffraction

Li

B

LiBH4 : DFT-MD PRL 108 095901 (2012)

ADPs = anisotropic displacement parameters (10% probabilities)

ADPs ensemble average

22

LiBH4: MODF – DFT molecular dynamics + diffraction LiBH4: MODF – DFT molecular dynamics + diffraction

Hydrogen ODF in BH4 (DFT MD) (ℓ = 5 spherical harmonic fit)

Hydrogen ODF in BH4 (DFT MD)

Hydrogen ODF in BH4 (neutron powder diffraction) (ℓ = 5 spherical harmonic fit)

c

LiBH4: NEMD-DFT verified by PDF + ADP + MODF LiBH4: NEMD-DFT verified by PDF + ADP + MODF

ADP

MODF LT – HT transition

24

LiBH4: diffusion mechanisms LiBH4: diffusion mechanisms

Acknowledgements

LiBH4 (GEM) Sam Callear (ISIS) LiBH4 (computational) Philippe Aeberhard (Oxford / ISIS) Stephen Williams (ANU) Denis Evans (ANU) Keith Refson (SCD, STFC)

RAL: ISIS & Diamond

ISIS TSII Oxford Chemistry Oxford

R 2016 | The semicentenary of the Rietveld Method

2016 | The centenary of powder diffraction

quinquagenary

golden jubilee