Synthesis and structural characterization of the new clathrates K8Cd4Ge42, Rb8Cd4Ge42, and Cs8Cd4Ge42

Abstract

This paper presents results from our exploratory work in the systems K-Cd-Ge, Rb-Cd-Ge, and Cs-Cd-Ge, which yielded the novel type-I clathrates with refined compositions K8Cd3.77(7)Ge42.23, Rb8Cd3.65(7)Ge42.35, and Cs7.80(1)Cd3.65(6)Ge42.35. The three compounds represent rare examples of clathrates of germanium with the alkali metals, where a d10 element substitutes a group 14 element. The three structures, established by single-crystal X-ray diffraction, indicate that the framework-building Ge atoms are randomly substituted by Cd atoms on only one of the three possible crystallographic sites. This and several other details of the crystal chemistry are elaborated.