Structure of rubidium–ammonium hexachlorotellurate [Rb0.8(NH4)0.2]2TeCl6 at room and low temperatures

Abstract The crystal structure of rubidium–ammonium hexachlorotellurate [Rb 0.8 (NH 4 ) 0.2 ] 2 TeCl 6 , has been determined by X-ray single crystal analysis at room and low temperatures (260 K). The space group at both temperatures is Fm 3 m with a ≈10.2 A, Z =4. The refinement converged, at room and low temperatures to R =0.021 and 0.011, respectively. The title compound has an antifluorite-type arrangement of NH 4 + /Rb + and octahedral TeCl 6 2− anions. At room temperature, the H atoms belonging to ammonium group exhibit a six-fold disorder about [1 1 1]. Decreasing of temperature induces an ordering of NH 4 + , evidenced by a three-fold H-disorder and a decreasing of the equivalent thermal values. IR and Raman spectroscopic studies at room temperature were performed to confirm results of the X-ray diffraction.