The true crystal structure of Li17M4 (M=Ge, Sn, Pb)–revised from Li22M5

Single crystal studies of the compounds Li17Ge4, Li17Sn4 and Li17Pb4, previously thought to be of stoichiometry Li22M5 (M=Ge, Sn, Pb) are presented. Their space group is F4̄3m, rather than the F23 previously reported for Sn and Pb, with a=18.756(2) Å, 19.690(2) Å and 19.842(1) Å for the Ge, Sn and Pb compounds, respectively, with very good refinements, particularly for the tin structure (R(F≥4σ(F))=1.85% for Ge, 1.91% for Sn and 2.3% for Pb). …