Bonding and electronic structure of sillenites

We performed first principles density functional theory calculations of Bi12GeO20, Bi12SiO20, and Bi12TiO20 sillenites compounds, in order to determine its bonding and electronic structure. Ultra-soft pseudopotential method based on GGA was used in order to relax the ion positions. Augmented Plane Wave (APW) method was used to investigate the electronic properties of three sillenites. We have compared the theoretical structure of the BiO7 polyhedron, and MO4 tetrahedra with the experimental data. The electron densities were used to analyze the lone pair from BiO7 polyhedron.