ON THE EFFICIENCY OF AN EFFECTIVE HAMILTONIAN IN SPIN-ORBIT CI CALCULATIONS

All-electron spin-orbit-CI calculations based on the pseudo relativist ic no-pair formalism have proven to give an adequate description of th e non-additive spin-orbit and correlation effects. Although methodolog ical and computational improvements have been achieved, the lack of si ze consistency and the dimension of the Hamilton matrix were found to be limitations for obtaining higher accuracy on compounds with heavy e lements. The use of an effective Hamiltonian at the pseudopotential le vel has been proposed to take account of dynamic correlation effects a t the spin-free level and to transfer this information to the iterativ e spin-orbit CI scheme. We have implemented this approach into a direc t all-electron SO-CI code. Applications to the platinum atom and to TI H have been carried out. (C) 1998 Elsevier Science B.V.