docCombined computational and neutron powder diffraction studies of
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Combined computational and neutron powder diffraction studies of
ISIS TSII Oxford Chemistry Oxford RAL: ISIS & Diamond Combined computational and neutron powder diffraction studies of disordered hydride structures Bill David, ISIS Facility, Rutherford Appleton Laboratory, UK & Inorganic Chemistry Laboratory, University of Oxford, UK 95A Real Crystallography of Real Materials under Real Conditions CO2 sequestration hydrogen stores lithium batteries fuel cells pharmaceuticals turbine blades nanomaterials C60 in operando proteins superhard graphite pencil “lead” novel techniques microstructure tensile stress paracetamol 2016 | The centenary of powder diffraction Neutron powder diffraction Hugo Rietveld “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.” ECN Petten, Netherlands (1966) The Rietveld Method Rietveld refinement The Rietveld Method 2016 | The centenary of powder diffraction 2016 | The semicentenary R of the Rietveld Method quinquagenary golden jubilee LiNH2 / Li2NH mobility topology non-stoichiometry Li(NH3)4 expanded metal Li4BN3H10 LiNH2BH3 Hd+-HdH2 ↑ Li2BNH6 Hd+-Hd(H2 ↑ liquid) one-shot hydrogen stores complex molecular anions NH3BH3 Hd+-Hddihydrogen bonding NH4BH4 LiBH4 superionic LiBH4 Li(NH3)BH4 ammonia stores LiBH4 ↔ Li(NH3)BH4 ↔ Li(NH3)2BH4 ↔ Li(NH3)3BH4 ↔ Li(NH3)4BH4 7Li11BD ISIS 4 : order and disorder 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 Refined HT crystal structure (perhaps there is disorder!) ZnS | wurtzite | space group P63mc HT-LiBH4 | space group P63mc LiBH4 : a PDF study of disorder B-D 1.22Å D-D 1.97Å B-D 1.21Å D-D 1.95Å 7Li11BD 4 : GEM (ISIS) LT-LiBH4 : powder diffraction – a conundrum 110.1o 111.2o 108.6o 107.1o LiBD4 | space group Pnma HT-LiBD4 ADPs (10% probability) Refined HT crystal structure (wurtzite analogue is not the place to start) HT-LiBH4 | space group P63/mmc HT-LiBH4 | space group P63mc HT-LiBH4 : introducing golf balls HT-LiBH4: the golf ball – 37 symmetry-independent “atomlets” 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 Y53 = -0.4892383*(9cos(th)^2-1 )*sin(th)^3 cos(3ph) 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 q f occ = 0.010989 = 2/182 = Y00*avo prm prm prm prm prm !avo 0.038955 C20 -0.03219`_0.00409 C33 0.55600`_0.00212 C40 -0.27161`_0.00508 C53 -0.11408`_0.00696 = 0.2820947918*avo ; avo =0.010989/0.2820947918 = 0.038955 LiBH4: ADPs ADPs Li B 20 ADPs = anisotropic displacement parameters (10% probabilities) LiBH4: ADPs – DFT molecular dynamics + diffraction ensemble average ADPs Li B LiBH4 : DFT-MD PRL 108 095901 (2012) 21 ADPs = anisotropic displacement parameters (10% probabilities) LiBH4: MODF – DFT molecular dynamics + diffraction Hydrogen ODF in BH4 (DFT MD) Hydrogen ODF in BH4 (DFT MD) (ℓ = 5 spherical harmonic fit) c Hydrogen ODF in BH4 (neutron powder diffraction) (ℓ = 5 spherical harmonic fit) 22 LiBH4: NEMD-DFT verified by PDF + ADP + MODF ADP MODF LT – HT transition LiBH4: diffusion mechanisms 24 ISIS TSII Oxford Chemistry Oxford Acknowledgements RAL: ISIS & Diamond LiBH4 (GEM) Sam Callear (ISIS) LiBH4 (computational) Philippe Aeberhard (Oxford / ISIS) Stephen Williams (ANU) Denis Evans (ANU) Keith Refson (SCD, STFC) 2016 | The centenary of powder diffraction 2016 | The semicentenary R of the Rietveld Method quinquagenary golden jubilee
