Hubbard U calculations on optical properties of 3d transition metal oxide TiO2

The optical properties of titanium dioxide (TiO2) in rutile, anatase and brookite phases were investigated via density functional theory (DFT) framework. The Hubbard U term in Ti 3d electrons of the TiO2 phases was introduced to observe the optical behavior with the effect of U parameter. The calculated structural parameters from the optimized TiO2 are in good agreement with the previous experimental and theoretical data. The values of static dielectric constant and refractive index from exchange-correlation functional in standard DFT are slightly higher than the DFT + U method. The energy peaks of reflectivity and loss function spectra show the good match with each other. The TiO2 with rutile, anatase and brookite phases have optical absorption in the ultraviolet (UV) light region. Thus, the inclusion of U parameters turn out to shift the wavelength photon towards the low region. Furthermore, this work provides a good theoretical understanding of the optical properties of TiO2 which helpful in a technological application such as photocatalysis and photovoltaics. (C) 2016 The Authors. Published by Elsevier B.V.