Ab initio calculation of the core-hole effect in the electron energy-loss near-edge structure

A computational scheme to fully account for the core-hole relaxation effect in electron energy-loss near-edge structure has been successfully implemen ted. Results on alpha-Al2O3, MgO, and MgAl2O4 crystals have reproduced all experimental details in all 11 edges. This is achieved by including three e ssential elements in the calculation: (1) A correct description of the pres ence of the hole in the core state of the excited atom. (2) The interaction between the excited electron in the conduction band and the hole left behi nd. (3) Use of large supercell for the final-state calculation. To a lesser extent, the inclusion of dipole matrix elements between the initial ground state and the final core-hole state is also important for the relative int ensity of the structures. It is shown that the wave function of the excited electron in the conduction band in the presence of the core-hole state is localized to within the second-nearest-neighbor atoms, and is significantly different from the conduction-band wave function obtained from the ground- state calculation.