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 crys tal. They are directly calculated from the self consistent charge dist ribution which is determined by the KKR method within the muffin-tin a pproximation 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 experi mental values were well reproduced. The electronic structure of these impurities is discussed by analyzing the calculated density of states.