Variation of hydrogen occupation in LaNi4.78Sn0.22Dx along the P-C isotherms studied by in situ neutron powder diffraction

The full hydride LaNi4.78Sn0.22D6.1 has a P6mm structure with four hydrogen sites; 3c sites (O[La2Ni4]), 6e1 sites (T[La2Ni2]), 6e2 sites (T[La1Ni3]) and 2b sites (T[Ni4]) with occupancies of 0.98(2), 0.34(1), 0.168(9) and 0.24(2), respectively. The 3c site was fully occupied regardless of the total hydrogen content. Occupancies of the other three sites changed depending on the hydrogen content, with hysteresis between absorption and desorption in the two-phase region. The hydrogen occupation and the lattice parameters for the hydride phase varied even in the two-phase region during desorption.