Excited States in Metal Oxides by Configuration Interaction and Multireference Perturbation Theory

Abstract

In this paper we address the study of optical and magnetic properties of metal oxides based on the cluster model approach and ab initio quantum chemistry techniques. Two different multireference approaches are used to compute the wave functions of the ground and the excited electronic states involved in optical transitions and magnetic interactions. The Difference Dedicated Configuration Interaction (DDCI) approach is a variational method based on the direct computation of energy differences between states. The Complete Active Space Self-Consistent Field (CASSCF) followed by Complete Active Space Second-Order Perturbation Theory (CASPT2) approach combines the Configuration Interaction (CI) techniques and many-body perturbation theory to account for electron correlation effects. Both methods turn out to be very suitable to estimate the differential electronic correlation and compute excitation energies. To illustrate the suitability of both methods, four applications are presented in this work: the study of d-d transitions and magnetic interactions in fcc transitionmetal oxides, and the study of excitonic and vacancy states in MgO.