Empirical Pseudopotential Method for Electronic Band Structure Calculations in Insulators

摘要

Electronic band structures are calculated by the 'Empirical Pseudopotential Method' for three ionic crystals: MgO, NaCl and KCl. The pseudopotential form factors of the first two crystals are determined by assuming the potentials are local. For the case of KCl, an additional angular momentum dependent nonlocal pseudopotential is introduced. The imaginary part of the frequency dependent dielectric function, epsilon sub 2 (omega), calculated from the band structure is directly compared to the measured ultraviolet spectrum. Apart from the excitonic structure, the agreement of the epsilon sub 2 (omega) between theory and experiment for the position in energy of the prominent structure is within 0.1 eV for photon energy less than 14.0 eV, and 1.0 eV for higher photon energy. There exists discrepancy between the magnitudes of the calculated and the measured peaks and this is discussed. The complete critical point analysis enables one to identify all the prominent structure in the epsilon sub 2 (omega). (Author)