Simple SCF method with spin-orbit interaction: SOSCF method

An equivalence restricted open-shell self-consistent field (SCF) method has been extended to include spin-orbit (SO) interaction for the variational calculation of individual SO sublevels both in the LS- and jj-coupling schemes. The method can be applied to simple atomic and molecular systems within an abelian point group with higher symmetry; e.g., C_2v, D₂, or D2_2h, in which the three rotational symmetries of R_x, R_y, and R₂ belong to distinct irreducible representations. Test calculations with relativistic effective core potentials (RECPs) by Christiansen and Ermler et al. are performed for most main-group p-block elements except for group 15, and for diatomic hydrides of group 14 and 16 elements, and the results are compared with previous theoretical and experimental data. In spite of the simplicity, our results are in reasonable agreement with the experimental data for most group 13 and 17 elements and for lighter group 14 and 16 elements. For heavier group 14 and 16 elements, however, the results in LS coupling become poorer due to the significant second-order SO effect. In such cases, the jj-coupling scheme yields better results, and the turning point between LS and jj preference was found between the fourth- and fifth-row elements.