A COULOMB HOLE APPROACH TO THE BINDING IN CR-2

The binding in Cr-2 is discussed from a semi-quantitative perspective. The static correlation contributions are accounted for by means of re stricted active space self-consistent held calculations. The short bon d distance in Cr-2 is understood to result mainly from near-degeneraci es due to states that include the binding 4d(pi) and 4d(delta) orbital s. A Coulomb hole expression is employed to estimate the remaining dyn amic correlation contributions. Connections are made with aspects of d ensity functional theory, the MGVB method, and recent CAS-PT2 studies.