Theoretical calculation of oxygen K electron-energy-loss near-edge structures of Si-doped MgO

Maximum solubility of Si in MgO has been reported to be 9.0 at.%. The local environment of the Si solute is of great interest. In order to foresee the difference of the O K-edge electron-energy-loss near-edge structure (ELNES) or x-ray absorption near-edge structure (XANES) due to the presence of the Si solute, first-principles molecular orbital calculations are performed using model clusters composed of 27 and 125 atoms that include a core hole. Extra peaks are found in the theoretical O K-edge photoabsorption cross section (PACS) of the Si-doped cluster. Their positions are found to depend strongly on the Si-O bond length. A realistic model cluster for the Si-doped MgO is constructed by total energy minimization using interatomic potentials. An Mg vacancy is included to keep the charge neutrality. The extra feature in the O K-edge PACS due to the presence of Si is then expected to be located mainly at the higher-energy shoulder of the main peak of the undoped MgO.