Comparative high-pressure study and chemical bonding analysis of Rh3Bi14 and isostructural Rh3Bi12Br2

The binary compound Rh3Bi14 was synthesized from the elements. The compound is isostructural with Rh3Bi12Br2, crystallizes with the orthorhombic space group Fddd (no. 70) and lattice parameters a=6.8959(15) Å, b=17.379(3) Å, c=31.758(6) Å. The crystal structure consists of a three-dimensional (3D) framework of edge-sharing cubes and square antiprisms (RhBi8/2). It is closely related to the intermetallic compound RhBi4, in which two Y-like frameworks of antiprisms interpenetrate. In Rh3Bi14 and Rh3Bi12Br2, additional bismuth and bromine anions, respectively, fill the channels of the 3D polyhedral framework formed by covalently bonded rhodium and bismuth atoms. High-pressure X-ray powder diffraction data from synchrotron measurements of Rh3Bi14 and Rh3Bi12Br2 indicate a high stability of both compounds in the investigated range from ambient pressure to ca. 30 GPa at ambient temperature.