1 Structural Studies of Metal-Hydrogen Interactions in Solid-State Metal Hydrides SINQ Users’ Meeting PSI, 27 Jan 2005 Yaroslav Filinchuk on behalf of the Laboratory of Crystallography University of Geneva

2 LaD 2+x Refined average D-atom displacements (  ) in octahedral interstices as a function of refined composition LaD 2+x Calculated atom relaxations (Å) around tetrahedral hydrogen vacancy in La 32 H 95 HRPT Renaudin et al., 2004 HRPT Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005

3 HRPT,  ~ 1.15 Å ErNi 3 : HRPT,  ~ 1.15 Å R-3m centro Single-crysal-like refinement from powder data ! Filinchuk et al., 2004

4 Deuteration on site, or in-situ R3m non-centro HRPT,  ~ 1.49 Å  1-ErNi 3 D 1.23(1) : HRPT,  ~ 1.49 Å Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Filinchuk et al., 2004

5 Alloy ErNi 3 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Filinchuk et al., 2004 HRPT

6  -deuteride ErNi 3 D 1.23 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Anisotropic cell expansion along c AB 2 block is filled with deuterium Filinchuk et al., 2004 Symmetry loss

7  -deuteride ErNi 3 D 1.97 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Isotropic cell expansion AB 5 block is partially filled with D Filinchuk et al., 2004 Trigonal prism [NiD 3 ]

8  -deuteride ErNi 3 D 3.75 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Anisotropic cell expansion along a AB 5 block is filled with deuterium Filinchuk et al., 2004 Tetrahedral [NiD 4 ] : similar to LaMg 2 NiD 7 & Mg 2 NiD 4 different from ErCo 3 D x & YCo 3 D x

9 LaNi 3 B LaNi 3 B → LaNi 3 BD Imma, oI20 → Cmcm, oC80 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Filinchuk et al., 2004

10 The unit cell is doubled along a and b LaNi 3 BH 2.7 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 HRPT

11 Two dimentional framework Ni-D D-Ni bond-valence sums are equal to 1 for each of 4 D-atom sites La 3+ B 0 [Ni 3 D 3 ] 3– Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Filinchuk et al., 2004 HRPT

12 DMC Temperature dependence of the cubic cell parameter and of deuterium occupancies in ZrTi 2 D 4.3 (from DMC data) Tokaychuk et al., 2004 Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 ZrTi 3 Zr 2 Ti 2 Fd-3m

13 Energy difference between the two deuterium sites in ZrTi 2 D x Dynamical hydrogen disorder 127 meV Metal to hydrogen interactions are important (!) Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005

14 Phase transitions in alkali borohydrides DMC Renaudin et al., 2004 DMC Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 Ordering of BD 4 - anion: Fm - 3 m to P4 2 /nmc Badger’s rule

15 ErCo 3 -D 2 : in-situ NPD, 60°C, 0-16 bar Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 DMC Filinchuk et al., 2004 DMC Conditions vacuum4.978(2) (18) 520.0(5) Little portions of D 2 let in 4.979(4) 24.25(3) 520.8(9)4.9837(16) (17) 547.7(4) 1.07(4) (9) (10) 551.7(2) 1.14(3) (8) (9) 553.3(2) 1.20(3) (9) (9) 557.0(2) 1.27(3) (9) (8) 560.1(2) 1.36(3) (9) (8) 561.3(2) 1.38(4) (10) (9) 561.7(2) 1.38(3)5.217(9) 26.21(9) 617(3) 2.5 bar D (10) (9) 561.5(3) 1.37(3)5.213(5) 26.16(4) 616(1) 2.5 bar D (13) (11) 561.2(3) 1.35(4)5.210(3) 26.14(3) 614.5(8) 3.0 bar D (4) 25.94(3) 560.7(10) (2) 26.07(2) 613.2(5) bar D (8) (7) 614.3(2) 3.84(6) 6 bar D (8) (7) 616.4(2) 3.91(6) 9 bar D (8) (7) 617.7(2) 4.13(5) 12 bar D (7) (6) 618.6(2) 4.17(5) 16 bar D (8) (7) 619.5(2) 4.20(6) 16 bar, 25°C (7) (6) 622.0(2) 4.30(5) phase diagram cell expansion deuterium content ErCo 3 ErCo 3 D 1.6 ErCo 3 D 4.0 Accurate structures from HRPT HRPT data DMC Magnetic structures: DMC ( K) Co-Co exchange interactions are correlated with Co-D bonding

16 Techniques used to study Metal-Hydrogen Interactions Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005 HRPT detailed investigation of complex structures in-situ NPD (tiny structural changes)DMC structure dynamics (hydrogen motion) in-situ NPD (complex phase diagrams) magnetic structures (M-M interactions) high-resolution NPD (phase transitions) Diffraction at SINQ Complementary Synchrotron powder & single crystal diffraction INS & Raman spectrosc. magnetic & el. properties ab-initio calculations

17 This work has been partially performed at the Swiss Spallation Neutron Source SINQ, Paul Scherrer Institute, Villigen, Switzerland We acknowledge the help of Denis Sheptyakov, Aziz Daoud-Aladine and Lukas Keller Y. Filinchuk SINQ Users’ Meeting, 27 Jan 2005