CASSCF/CI calculations of electronic states and potential energy surfaces of PtH2

Abstract

Complete active space MCSCF followed by MRSDCI (multireference singles and doubles configuration interaction) calculations are carried out on the electronic states of PtH2. Spin–orbit interaction is introduced using a relativistic configuration interaction scheme on PtH+ whose d orbital Mulliken population is close to that of the d population of PtH2 and thus enables calculation of spin–orbit splittings for the electronic states of PtH2. The bending potential energy surfaces of the 1A1 and 3A1 states are obtained. The 1A1 surface has a bent minimum and dissociates almost without a barrier into Pt(1S0) and H2, while the 3A1 state has a large (∼55 kcal/mol) barrier to dissociation into Pt(3D3)+H2. The ground state of PtH2 is a bent 1A1 state (θ=85°).