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  Kunkel, N.; Reichert, C.; Springborg, M.; Wallacher, D.; Kohlmann, H.: Hydrogenation properties of Li_xSr_1-xAlSi studied by quantum-chemical methods (0≤x≤1) and in-situ neutron powder diffraction (x=1). Journal of Solid State Chemistry 211 (2015), p. 318-324

10.1016/j.jssc.2014.10.021

Abstract:
In-situ neutron powder diffraction studies of the Half-Heusler phase LiAlSi under high deuterium pressures and first principle calculations of solid solutions of LixSr1−xAlSi and their hydrides LixSr1−xAlSiH were carried out. In contrast to an earlier study, there is no experimental evidence for hydrogen (deuterium) uptake up to gas pressures of 15 MPa and temperatures of 550 °C. Instead a slow decomposition reaction according to LiAlSi+1/2H2=LiH+Al+Si was found by in-situ neutron powder diffraction. Theoretical calculations by DFT methods on hypothetical solid solutions of LixSr1−xAlSi show the LiAlSi type to be the energetically most stable structure for 0.7<x and the SrAlSi type structure for lower values of x. Hydrides LixSr1−xAlSiH favor the SrAlSiH type for all values of x instead of the structure proposed earlier with hydrogen occupying tetrahedral voids in a LiAlSi structure. As an alternative for a cubic structure for LiAlSiH, we suggest the existence of LiAlSiH in the trigonal SrAlSiH type structure and it might be a candidate worthwhile to be considered for preparative work.