Spin-Orbit Splittings in the Third-Row Transition Elements: Comparison of Effective Nuclear Charge and Full Breit-Pauli Calculations

The spin−orbit splittings of low-lying states in third-row transition elements were calculated using both an effective core potential (ECP) method within the one-electron (Zeff) approximation and all-electron (AE) methods using three different approaches. The wave functions were obtained using the multiconfiguration self consistent field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations. All calculated results, except for the ones on atomic Ir, are in reasonable agreement with the corresponding experimental observations. The unsatisfactory results for atomic Ir are attributed to the poor theoretical prediction of the adiabatic energy gap between the lowest two 4F states. This gap has an incorrect sign in AE calculations without scalar relativistic corrections, but the gap can be reproduced qualitatively if these corrections are added using the newly developed RESC (relativistic elimination of small components) scheme. As a result, the AE calculations with the RESC approximation give spin−orbit splittings similar to those obtained by the ECP calculations with the Zeff approximation. Disciplines Chemistry Comments Reprinted (adapted) with permission from Journal of Physical Chemistry A 105 (2001): 8262, doi:10.1021/ jp011677r. Copyright 2001 American Chemical Society. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/chem_pubs/389 Spin-Orbit Splittings in the Third-Row Transition Elements: Comparison of Effective Nuclear Charge and Full Breit-Pauli Calculations Shiro Koseki,*,† Dmitri G. Fedorov,‡,§ Michael W. Schmidt,‡,| and Mark S. Gordon*,‡ Chemistry Department for Materials, Faculty of Engineering, Mie UniVersity, Tsu 514-8507, Japan, and Department of Chemistry, Iowa State UniVersity, Ames, Iowa 50011 ReceiVed: May 3, 2001 The spin-orbit splittings of low-lying states in third-row transition elements were calculated using both an effective core potential (ECP) method within the one-electron (Zeff) approximation and all-electron (AE) methods using three different approaches. The wave functions were obtained using the multiconfiguration self consistent field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations. All calculated results, except for the ones on atomic Ir, are in reasonable agreement with the corresponding experimental observations. The unsatisfactory results for atomic Ir are attributed to the poor theoretical prediction of the adiabatic energy gap between the lowest two 4F states. This gap has an incorrect sign in AE calculations without scalar relativistic corrections, but the gap can be reproduced qualitatively if these corrections are added using the newly developed RESC (relativistic elimination of small components) scheme. As a result, the AE calculations with the RESC approximation give spin-orbit splittings similar to those obtained by the ECP calculations with the Zeff approximation.