Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

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The electronic structure, charge distribution, effective charge, and charge transfer in ferroelectric tetragonal are carefully studied using a local density functional potential and a self-consistent ab initio LCAO (linear combination of atomic orbitals) method. It is shown that the band gap and low-energy conduction band can be calculated with a reasonable accuracy when the ab initio LCAO method is used with an optimum basis set of atomic orbitals. The calculated optical spectrum, band gap, and effective mass of , obtained from the calculated electronic structure, are in good agreement with experimental results.