Electronic and optical properties of nickel doped potassium titanate nanostructures: A DFT study

The electronic and optical properties of nickel doped potassium titanate (KTO) nanostructures are studied theoretically by using density functional theory (DFT). The crystal structure for the nickel doped potassium titanate nanostructures are compared with the undoped samples of the same which is used for calculating the band gap energies and optical spectra. The plane-wave-based density functional theory (DFT) calculations are performed using the Quantumwise ATK version 11.8.2 with local-density approximation(LDA), generalized gradient approximation (GGA) for both the undoped and nickel doped potassium titanate nanostrucrures. The band structure calculated for doped potassium titanate is found to be 0 eV for all the approximations. However, the band structure of undoped potassium titanate calculated by LDA, GGA is found to vary from 1.2 eV to 8 eV. Therefore, it can be said that the doping of Nickel in the pure sample causes a decrease in band gap energy of the materials. The optical spectra of doped and undoped potassium titanate nanostructures are obtained and it can be seen that the variation of band gap energy values derived from the optical spectra is similar to those calculated from the band structure. The calculations with GGA, LDA functional are also compared with the existing theoretical & experimental data which shows a reasonably good agreement with the values calculated by using other methods.