On the Absence of Doubly Bonded Te=O Groups in TeO2 Glass

Tellurium oxide clusters (TeO2)(6) were investigated through density functional theory to gain information on the structure of TeO2 glass. Among a large number of stable conformers studied, a cyclic, nonsymmetric structure was optimized without terminal Te=O double bonds. The dimer of this structure, (TeO2)(12), gives calculated Raman and infrared spectra in very good agreement with the experimental ones, with its total pair distribution function being also in agreement with results of neutron and high-energy X-ray diffraction studies. The (TeO2)(12) cluster consists mainly of TeO4 units connected by asymmetric and nearly symmetric Te-O-Te bridges as in gamma-TeO2 and involves also edge-sharing through double-oxygen Te-O-2-Te bridges as in the beta-TeO2 polymorph. The optimized cluster structure is slightly unstable compared to the calculated global minimum structure, suggesting a kinetically stable product similar to its corresponding experimental TeO2 glass.