Synthesis and Structural Characterization of the New Clathrates K8Cd4Ge42, Rb8Cd4Ge42, and Cs8Cd4Ge42

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) Ge-42.23, Rb8Cd3.65(7) Ge-42.35, and Cs-7.80(1) Cd-3.65(6) Ge-42.35. The three compounds represent rare examples of clathrates of germanium with the alkali metals, where a d(10) 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.