Quantum chemical modelling of perovskite solid solutions

In line with our previous study (Eglitis R I et al 1998 J. Phys.: Condens. Matter 10 6271) for a single Nb impurity and Nb clusters in KTaO3 we presen t here the results of calculations for a series of perovskite KNbxTa1-xO3 ( KTN) solid solutions (x = 0, 0.125, 0.25, 0.75, and 1). The quantum chemica l method of the intermediate neglect of the differential overlap (INDO) com bined with the large unit cell (LUC) periodic model is used. According to t he INDO calculations, Nh impurity becomes off-centre in KTaO3 already at th e lowest studied Nb concentration. Its off-centre displacement is in a good agreement with XAFS measurements. We compare our results with previous FP- LMTO calculations.