All-Electron Molecular Dirac-Hartree-Fock Calculations: The Group 4 Tetrahydrides Ch4, Sih4, Geh4, Snh4 and Pbh4

A basis-set-expansion Dirac-Hartree-Fock program for molecules is described. Bond lengths and harmonic frequencies are presented for the ground states of the group 4 tetrahydrides, CH4, SiH4, GeH4, SnH4, and PbH4. The results are compared with relativistic effective core potential (RECP) calculations, first-order perturbation theory (PT) calculations and with experimental data. The bond lengths are well predicted by first-order perturbation theory for all molecules, but non of the RECP's considered provides a consistent prediction. Perturbation theory overestimates the relativistic correction to the harmonic frequencies; the RECP calculations underestimate the correction. Dyall, Kenneth G. and Taylor, Peter R. and Faegri, Knut, Jr. and Partridge, Harry Ames Research Center NCC2-552; NCC2-371...