Semi-empirical defect calculations for the perovskite KNbO3

A new parametrization of the classical shell model for the cubic phase of t he perovskite KNbO3 has been derived and used to calculate the structural, elastic and dielectric properties of this material. Using this parametrizat ion, the defect formation and migration energies,as well as atomic displace ments, have been calculated. In parallel, the quantum mechanical method of the intermediate neglect of the differential overlap (INDO) has been applie d to the same problem. The migration energies for the O vacancy obtained by these quite different methods are reasonably close (0.68 eV and 0.79 eV, r espectively) and also agree with the only experimental estimate available o f approximately 1 eV. Atomic relaxations calculated by these two methods ag ree quite well.