Improved generator coordinate Hartree-Fock method for molecular systems: application to H-2, Li-2 and LiH

The improved generator coordinate Hartree-Fock (GCHF) method is extended to molecular systems. The Griffin-Hill-Wheeler-HF equations were solved by an integral discretization technique. The method is then implemented with the use of the GAMESS program and applied to the H-2, Li-2, and LiH molecules. For these molecules, sequences of basis sets of atom-centred Gaussian-type functions are employed to explore the accuracy achieved with our approach. For all systems studied, our ground-state HF total energies are better tha n those obtained with basis sets generated with the original GCHF method fo r molecules and larger even-tempered basis sets. For H-2, Li-2, and LIH, th e differences between our best energies and the corresponding numerical HF results are about 2 x 10(-2), 1, and 4 x 10(-1) mu hartree, respectively. T he dipole, quadrupole, and octupole moments at the center of mass and elect ric held, the electric field gradient, the electrostatic potential, and the electron density at the nuclei were evaluated and compared with results re ported in the literature.