The Dirac equation in the algebraic approximation. VI. Molecular self-consistent field studies using basis sets of Gaussian-type functions

Abstract

The matrix Dirac-Hartree-Fock equations are presented for molecular systems of arbitrary symmetry. The advantages of using basis sets of Gaussian-type functions in relativistic self-consistent field calculations are described. Prototype calculations for the ground state of the HCl molecule at three geometries close to the experimentally determined equilibrium geometry are presented and discussed. Relativistic energies are compared with basis set truncation effects and non-relativistic electron correlation energies and their geometry dependence is analysed. The accuracy with which the non-relativistic limit can be approached by multiplying the speed of light c by a scalar p and allowing lambda =pc to become large is investigated. Dipole moments are calculated.