D. Krause et M. Klobukowski, ON THE PERFORMANCE OF MOLECULAR-MODEL CORE POTENTIAL ORBITALS IN SPIN-ORBIT AND ELECTRON CORRELATION STUDIES, Canadian journal of chemistry, 74(6), 1996, pp. 1248-1252
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 effec
ts (in P-2, As-2, and Sb-2). An effective method of identifying and re
moving the intruder quasi-core orbitals from the virtual orbital space
was proposed in connection with the post-Hartree-Fock calculations. T
he 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 quasicore orbitals, even if left imbe
dded in the virtual space, have negligible effect on the values of the
electron correlation energy.