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. © 1994 John Wiley & Sons, Inc.