Natural surface oxidation consideration in first principles modeling of the X-ray absorption near edge fine structure of silicon

•Si surface covered by natural oxide electronic structure first principles calculation.•High resolution XANES modeling of Si surface covered by natural oxide.•A significant effect of Si surface natural oxidation on surface electronic structure. First-principles calculations of the electronic structure of crystalline silicon and its dioxide were performed on the basis of the density functional theory. The full-potential linearized augmented plane waves method was used with the generalized gradient approximation for the exchange-correlation potential with Perdew, Burke and Ernzerhof functional. X-ray absorption near edge structure of silicon L3 spectra for these materials were calculated with the use of core-hole approach and supercells. These calculated spectra were used as reference for modeling the X-ray absorption L3 spectrum of a real silicon sample covered with a layer of natural SiO2 oxide. Comparison of the spectra obtained by the first principles calculations with the results of a high-resolution synchrotron experiments and the suggested approach to their modeling demonstrated the possibility of a complex silicon-oxygen system prospective materials and structures detailed study.