A b i n i t i o effective core potentials including relativistic effects. V. SCF calculations with ω–ω coupling including results for Au2+, TlH, PbS, and PbSe

Abstract

Ab initio self‐consistent field calculations are reported for a series of diatomic molecules using relativistic effective core potentials (REP) and basis sets appropriate for ω–ω coupling. The molecular orbitals are expressed as linear combinations of two‐component analogs of Dirac spinors. The unique feature of the present approach is the retention of the spin–orbit operator in the generation of the REP’s and the propagation of its effects into the molecular wave functions in a totally consistent fashion. The nature of bonding in the molecules Au₂⁺, TlH, PbSe, and PbS is discussed with consideration of the orbital energies, spectroscopic constants, and population analyses. Comparisons with recently obtained photoelectron spectra of PbSe and PbS are made. It is noted that 6p_1/2 and 6p_3/2 orbitals exhibits bonding characteristics that are different from the nonrelativistic pσ and pπ molecular orbitals.