Calculation of molecular geometries by SCF perturbation theory

An SCF perturbation method for investigating the effects of an arbitrary change in nuclear configuration on the electronic structure of a molecule is reported. Illustrative calculations for CO2 and CH3OH are presented. It is found that, when taken to second order, the error in the calculated change in energy which results from a change in nuclear configuration is typically in the range of 0.1 to 7%.