THE 2ND-ORDER ENERGY CONTRIBUTION FROM THE SPIN ORBIT INTERACTION OPERATOR TO THE POTENTIAL-ENERGY CURVE OF CR-2

The second-order Rayleigh-Schrodinger energy correction to the Born-Oppenheimer potential energy due to the spin-orbit interaction can be expressed as a linear response function evaluated at zero frequency. We have calculated this energy contribution to the Cr2 singlet ground state-CHI-1-SIGMA(g)+ potential energy function for a multiconfiguration self-consistent field (MCSCF) wave function. The calculations show that the effect of spin-orbit interaction is small and of the same magnitude for the whole potential energy curve.