The ab initio model potential method with the spin-free relativistic scheme by eliminating small components Hamiltonian

A relativistic ab initio model potential (AIMP) for Pt, Au, and Hg atoms ha s been developed using a relativistic scheme by eliminating small component s (RESC) in which the 5p, 5d, and 6s electrons are treated explicitly. The quality of new RESC-AIMP has been tested by calculating the spectroscopic p roperties of the hydrides of these elements using the Hartree-Fock and coup led cluster with singles and doubles (CCSD) methods. The agreement with ref erence all-electron RESC calculations is excellent. The RESC-AIMP method is applied successfully in the investigation of the spectroscopic constants o f Au-2 and Hg-2 using the CCSD method with a perturbative estimate of the c ontributions of triples. The ground state of Pt-2 is also determined by RES C-AIMP with the second-order complete active space perturbation method. The results show that scalar relativistic effects on the valence properties ar e well described by the RESC-AIMP method. The effect on the basis set super position error on the spectroscopic constants is also examined. (C) 2001 Am erican Institute of Physics.