High-pressure synthesis and crystal structure of Sr2MgH6

Abstract

Abstract Sr 2 MgH 6 has been prepared by subjecting binary SrH 2 and MgH 2 in a 2:1 molar ratio by solid state reaction at T =870 K under quasi-hydrostatic pressure of 35 kbar during 200 minutes, and investigated by neutron powder diffraction on its deuteride. It crystallises with the K 2 GeF 6 -type structure (space group P3m1 , Z =1; cell parameters at 293 K for the hydride a =5.5610(6), c =4.1708(5) A, V =111.7 A 3 , and the deuteride a =5.5458(2), c =4.1630(2) A, V =110.9 A 3 ). Magnesium has a nearly octahedral deuterium coordination with bond distances Mg−D=2.03 A, and strontium a twinned cuboctahedral deuterium coordination with bond distances in the range Sr–D=2.50–2.78 A. It decomposes at about 650 K and 5 bar deuterium pressure into SrD 2 and Mg.