Calculations of radiation-induced point defects, polarons and excitons in ferroelectric perovskites

We review results of our recent large-scale computer simulations of radiation-induced point defects, excitons and polarons in ABO₃ perovskite crystals, focusing mostly on KNbO₃ and KTaO₃ as representative examples. We have calculated the atomic and electronic structure of defects, their optical absorption, defect-induced electron density redistribution, and activation energies for defect migration. The majority of our results were obtained using the quantum-chemical method of the intermediate neglect of differential overlap (INDO) based on the Hartree-Fock formalism, as well as the shell model (SM). The main findings are compared with those obtained by means of ab initio density functional theory (FP-LMTO) first-principles calculations.