Ab initio calculation of chain structures in chalcohalide glasses

Local structure of Te3X2 (X = Cl, Br) chalcohalide glasses were studied using ab initio molecular orbital (MO) theory. The calculation results were compared with Mössbauer spectroscopic parameters in terms of electric-field gradient and electron density at each Te site. In addition, the existence of terminal bond –Te–X was examined. The MO analysis of Te-chain and Te-chain with Cl atoms within a picture of the frontier orbital theory elucidated that the localized orbital at –TeCl2– site is important to form tellurium halide glass.