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 a ll-electron calculations, a recently developed atomic mean-field spin- orbit code succeeded in reproducing spectroscopic data with high accur acy. We propose a new way to combine these approaches in order to bene fit from their conceptual and computational advantages. We present app lications on two experimentally and/or theoretically well-known atomic systems, platinum and thallium, to prove the validity and precision o f this new ansatz. (C) 1998 Elsevier Science B.V.