Regular approximated scalar relativistic correlated ab initio schemes: applications to rare gas dimers

The ab initio scalar ZORA approach, which was previously tested within the context of numerical and basis set SCF calculations, is generalized to include electron correlation. The technical details of the method are investigated in calculations on the systems Ne2, Ar2, Kr2 and Xe2. For the weakly bonded rare gas dimers we calculated the bond lengths and well depths using the non-relativistic ZORA and scaled ZORA MP2 method. The relativistic effect on the potential energy minimum, obtained with the most accurate method (scaled ZORA) is shown to be very close to that of the Dirac-Fock MP2 method.