Ab initio calculations of electric field gradients for transition metal impurities in TiO2

We present ab initio calculations of EFGs at impurities in a TiO2 crystal. They are directly calculated from the self consistent charge distribution which is determined by the KKR method within the muffin-tin approximation and based on the local density approximation. Impurities in the crystal are simulated by the super-cell method. Considering the charge state of Sc, Ti, Nh, Cd, Ta impurities in the TiO2, the experimental values were well reproduced. The electronic structure of these impurities is discussed by analyzing the calculated density of states.