FORCE CONSTANTS AND DIPOLE MOMENT DERIVATIVES OF MOLECULES FROM PERTURBED HARTREE-FOCK CALCULATIONS

Author Institution: Department of Chemistry, Harvard University; Department of Chemistry, University of ReadingThe accuracy of the Hartree-Fock wave function for a closed shell molecule is not confined to one-electron properties only, but also includes force constants (and all other second order properties arising from one-electron perturbations to the Hamiltonian). A general perturbed Hartree-Fock theory has been developed which makes possible the calculation of force constants and dipole moment derivatives directly from extended basis set SCF-MO wave functions. Essentially one calculates the quantities $\partial \phi/\partial R^{\alpha}_{J}$, the first derivative of an MO with respect to a nuclear coordinate. The theory has been applied to simple limited basis set SCF-MO wave functions for LiH, BH, and HF, and the results show that the calculations are indeed technically feasible, and give physically meaningful results even for such simple wave functions