On the performance of molecular model core potential orbitals in spin-orbit and electron correlation studies

Abstract

The role of improved parametrization and accurate basis sets in model core potentials was studied in calculations of the spin-orbit coupling constants (in PH, AsH, and SbH) and of the electron correlation effects (in P2, As2, and Sb2). An effective method of identifying and removing the intruder quasi-core orbitals from the virtual orbital space was proposed in connection with the post-Hartree–Fock calculations. The results demonstrated that (a) the flexible valence basis sets allow evaluation of the spin-orbit effects without resorting to any scaling techniques and (b) the intruder quasi-core orbitals, even if left imbedded in the virtual space, have negligible effect on the values of the electron correlation energy. Key words: effective core potentials, basis sets, spin-orbit effects, electron correlation.