First principles calculation of optical properties of BaWO4: A study by full potential method

We report on the first principles calculations of electronic and optical properties of barium–tungstate (BaWO4) crystal. The frequency dependence of optical properties has been calculated using a full potential linearized augmented plane wave (FP-LAPW) method as embodied in the Wien2k code in the frame work of density functional theory (DFT). The calculations suggest BaWO4 to be a negative crystal having a birefringence of about 0.15. Uniaxial anisotropy and plasmon energy for the crystal were calculated as 0.0624 and 13.5 eV, respectively. The calculations also show BaWO4 to be a direct band gap crystal having less dispersive valence and conduction bands and in contrast to other Scheelites crystals like PbWO4, the cationic states do not contribute to the main part of the valence/conduction bands. The experimentally measured energy band gap (4.9 eV) matches well with the calculated value 4.1 eV of the present work. A detailed analysis clearly revealed the differences in the optical properties of BaWO4 crystal as compared with other Scheelites.