Crystal chemistry peculiarities of Cs2Te4O12

The Raman and IR-absorption spectra of the Cs2Te4O12 lattice are first recorded and interpreted. Extraordinary features observed in the structure and Raman spectra of Cs2Te4O12 are analyzed by using ab initio and lattice-dynamical model calculations. This compound is specified as a caesium-tellurium tellurate Cs2TeIV(TeVIO4)3 in which TeIV atoms transfer their 5p electrons to [TeVIO4]36− tellurate anions, thus fulfilling (jointly with Cs atoms) the role of cations. The TeVI–O–TeVI bridge vibration Raman intensity is found abnormally weak, which is reproduced by model treatment including the Cs+ ion polarizability properties in consideration.