On the consistent definition of spin-orbit effects calculated by relativistic effective core potentials with one-electron spin-orbit operators: Comparison of spin-orbit effects for Tl, TlH, TlH3, PbH2, and PbH4

The spin-orbit effects for Tl, TlH, TlH3, PbH2, and PbH4 are evaluated by t wo-component calculations using several relativistic effective core potenti als (RECP) with one-electron spin-orbit operators. The used RECPs are shape -consistent RECPs derived by Wildman et al. [J. Chem. Phys. 107, 9975 (1997 )] and three sets of energy-consistent (or adjusted) RECPs published by Sch werdtfeger et al. [Phys. Scr. 36, 453 (1987); J. Chem. Phys. 90, 762 (1989) ], Kuchle et al. [Mol. Phys. 74, 1245 (1991)], and Leininger et al. [Chem. Phys. 217, 19 (1997)]. The shape-consistent RECP results are in very good a greement with the Kuchle et al. energy-consistent RECP results for all the molecules studied here and all-electron results for TlH. The RECPs of Schwe rdtfeger et al. and Leininger et al. seem to provide qualitatively differen t spin-orbit effects. If one defines spin-free RECP as the potential averag e of the corresponding two-component RECP, all RECPs give very similar spin -orbit effects for all the cases. Most of the discrepancies of molecular sp in-orbit effects among various RECPs reported in the literature may origina te from different definitions of RECPs with or without a spin-orbit term an d not from the inherent difference in spin-orbit operators. (C) 1999 Americ an Institute of Physics. [S0021-9606(99)30219-1].