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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