THEORETICAL-ANALYSIS OF X-RAY-ABSORPTION SPECTRA AT THE SILICON K ANDL(2,3) EDGES OF CRYSTALLINE AND AMORPHOUS SIO2

In this work we present the analysis of the x-ray-absorption spectra a t the silicon L(2,3) and K edges in amorphous SiO2 and alpha quartz. T his analysis consists in the comparison between experimental data and several calculations based on multiple scattering theory. An extensive discussion is presented concerning the role of the final state potent ial needed to reproduce the experimental data. In particular, the effe cts of the cluster-size, exchange-correlation potential and the role p layed by self-consistent-field potential are discussed. The remarkable agreement between the theoretical computations and the experimental d ata allows us to identify the origin of the different features in the x-ray-absorption near-edge structure spectra.