Calculation of XANES/ELNES Spectra of All Edges in Si3N4 and Si2N2O

Abstract

Using a recently developed first-principles supercell method that includes the electron and core-hole interaction, the XANES/ELNES spectra of Si-L 2,3 , Si-K, and N-K edges in α-Si 3 N 4 , β-Si 3 N 4 , spinel c-Si 3 N 4 , and Si 2 N 2 O were calculated and compared. The difference in total energies between the initial ground state and the final core-hole state provides the transition energy. The calculated spectra are found to be in good agreement with the experimental measurements on β-Si 3 N 4 and c-Si 3 N 4 . The differences in the XANES/ELNES spectra for the same element in different crystals are explained in terms of differences in local bonding. The use of orbital-decomposed local density of states to explain the measured spectra is shown to be inadequate. These results reaffirm the importance of including the core-hole effect in any XANES/ ELNES spectral calculation.