Ab initio calculations of the electronic structure and optical properties of ferroelectric tetragonal BaTiO3

The electronic structure, charge distribution, effective charge, and charge transfer in ferroelectric tetragonal BaTiO3 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 BaTiO3, obtained from the calculated electronic structure, are in good agreement with experimental results.