Extension and application of calculation method utilizing relativistic effective core potentials

Abstract

We implemented two-component effective core potential integrals based on ARGOS routine on the DIRAC program. This introduces an alternative way of including spin-orbit effects via valence-only Hamiltionian and extends the horizon of effective core potential calculation. As a test, we calculated the hydrogen halides. Calculations were also carried out at higher levels of theory such as second order MØller-Plesset theory (MP2), coupled-cluster single and double excitations (CCSD), and CCSD with perturbatively triple excitations (CCSD(T)). Comparisions are made with previously obtained values from various different methods and experiments. After establishing the reliability of the methods through test calculations, we extended the calculations to hydrogen bihalide systems to estimate geometries and binding energies