CORE-HOLE EFFECT ON THE XAS SI K-EDGE SHAPE IN ALPHA-QUARTZ

The role of the core hole effect on the Si K X-ray absorption spectrum of alpha-quartz is established thanks to two electronic structure calculations: 1. a self-consistent band structure approach at ambient pressure and under hydrostatic pressure, that accounts for the gap and the valence band shape, and that provides the empty density of states of alpha-quartz, is shown to be unable to reproduce the experimental Si K edge shape; 2. on the opposite, a self-consistent embedded cluster calculation, which allows to include the effect of the core hole yields a local p density of states on an excited silicon atom which compares satisfactorily with the experimental spectrum.