Ab initio study of the ground and lower-lying excited electronic states of CoF2, CoCl2, CoBr2 and CoI2

Abstract

The ground and lower-lying excited electronic states of CoX2 (X = F, Cl, Br, I) were investigated systematically by ab initio methods. The complete active space self-consistent field (CASSCF) and multiconfigurational quasi-degenerate second-order perturbation (MCQDPT2) levels of theory were employed. It was concluded that the dynamic electron correlation has to be taken into account in the prediction of the properties for such molecules. According to the results of the MCQDPT2 calculations, all investigated molecules have the linear equilibrium configuration and the 4Δg ground state. The equilibrium bond lengths r e(Co−X), force constants and harmonic vibrational frequencies were calculated for the ground and lower-lying excited electronic states. The Renner effect of bending vibrations was estimated to be very small.