On the combination of ECP-based CI calculations with all-electron spin-orbit mean-field integrals

Spin-orbit interaction in ab initio calculations using effective core potentials is usually treated with pseudo-spin-orbit-op erators, which are fitted on relativistic all-electron data. This procedure has been applied successfully for many systems. However, in combination with all-electron calculations, a recently developed atomic mean-field spin-orbit code succeeded in reproducing spectroscopic data with high accuracy. We propose a new way to combine these approaches in order to benefit from their conceptual and computational advantages. We present applications on two experimentally and/or theoretically well-known atomic systems, platinum and thallium, to prove the validity and precision of this new ansatz. (C) 1998 Elsevier Science B.V.