Bonding and Electronic Properties of Cs₃Te₂₂

The compound Cs3Te22 is well-known for its interesting structural features. It contains both a unique 2,3-connected defect square Te sheet and Te8 rings. For a better understanding of the structure and bonding, the band structure of Cs3Te22 is examined by means of the ab initio tight-binding linear muffin-tin orbital (TB-LMTO) method, which is based upon density functional theory (DFT). The calculations are complemented by an analysis of the electronic density topology with the electron localization function (ELF) and a traditional orbital analysis using the projected density of states (DOS) and the crystal orbital Hamiltonian population (COHP). Our study indicates that the short Te-Te contacts between Te₈ rings and the defect Te₆^3- sheet in this compound have a direct influence upon the properties of this material. The presence of this interaction perturbs the electronic density relative to that which one obtains from analysis of the isolated defect sheet and leads to favorable conditions for an insulator state.