Accurate ab initio potential energy curve of F2. II. Core-valence correlations, relativistic contributions, and long-range interactions.

The nonrelativistic, valence-shell-only-correlated ab initio potential energy curve of the F(2) molecule, which was reported in the preceding paper, is complemented by determining the energy contributions that arise from the electron correlations that involve the core electrons as well as the contributions that are due to spin-orbit coupling and scalar relativistic effects. The dissociation curve rises rather steeply toward the energy of the dissociated atoms because, at larger distances, the atomic quadrupole-quadrupole repulsion and spin-orbit coupling counteract the attractive contributions from incipient covalent binding and correlation forces including dispersion.