Revisiting the Si-Te System: SiTe2 Finally Found by Means of Experimental and Quantum-Chemical Techniques.

Through explorations of the silicon-tellurium system we identified the extremely air-sensitive, red Si1.67(4)Te3≡Si1.11(3)Te2 that is a silicon-deficient relative of the previously reported Si2Te3. The crystal structure features hexagonal closest packed layers of tellurium atoms with disordered [Si2] dumbbells residing in about 50% of the octahedra of every second layer enclosed by the tellurium atoms. In addition to the determination of the crystal structure for this silicon telluride, we probed the opportunity of the existence of a SiTe2 adopting the Si2Te3-structure by means of quantum chemical techniques. The investigations of the electronic structures and a subsequent chemical bonding analysis based on the projected Crystal Orbital Hamilton Population (pCOHP) technique for two "SiTe2" models revealed a tendency to align the [Si2] dumbbells parallel to the c axis to maximize Si-Te bonding. However, the disorder of the [Si2] dumbbells appears to be a consequence of non-equilibrium condensation into the solid state.