First-principles Calculation of Transition-metal L_2,3-edge Electron-energy-loss Near-edge structures Based on Direct Diagonalization of the Many-electron Hamiltonian

Abstract

First-principles relativistic configuration-interaction (CI) calculations of cation L_2,3-edge electron-energy-loss near-edge structures (ELNES) of SrTiO₃, NiO and CaF₂ have been carried out based on the direct approach where the ground state (GS) configuration and the excited state (ES) configuration were calculated simultaneously by direct diagonalization of the many-electron Hamiltonian. The obtained theoretical spectra were compared with our recent results based on the indirect approach where the GS configuration and the ES configuration were calculated separately and their energy separation was adjusted to the value predicted by the Slater’s transition-state calculation. Although both approaches well reproduced the overall features of the experimental spectra, the direct approach tend to slightly overestimate the absolute transition energies. In the case of Ti L_2,3-edge of SrTiO₃, however, the absolute transition energies calculated by the direct approach were comparable to those by the indirect approach and were also in good agreement with experimental values, indicating sufficient inclusion of electron correlations through pure configuration interactions.