Unoccupied electronic states of stishovite: X-ray absorption fine structure theoretical analysis

Previously observed core level near edge spectra (Si K-and Si L2,3 XANES, and O K-edge EELS) for the high-pressure SiO2 polymorph stishovite have been calculated using “ab initio” full multiple-scattering theory. Good agreement between theory and experiment has been obtained. The distribution of the unoccupied projected silicon s, and d antibonding states and oxygen p antibonding states has been established. Interactions between these states in the bottom part of the conduction band of stishovite have been studied. A special kind of hybridization has been found. It has been shown that as a result of the interaction between Si s and p states and O p states, O p states are “squeezed out” of the energy region of the Si s and p antibonding states.