Relativistic coupled cluster theory based on the no-pair dirac-coulomb-breit hamiltonian: Relativistic pair correlation energies of the xe atom

Relativistic pair correlation energies of Xe were computed by employing a recently developed relativistic coupled cluster theory based on the no-pair Dirac–Coulomb–Breit Hamiltonian. The matrix Dirac–Fock–Breit SCF and relativistic coupled cluster calculations were performed by means of expansion in basis sets of well-tempered Gaussian spinors. A detailed study of the pair correlation energies in Xe is performed, in order to investigate the effects of the low-frequency Breit interaction on the correlation energies of Xe. Nonadditivity of correlation and relativistic (particularly Breit) effects is discussed.