title: Communication: Two-determinant mixing with a strong-correlation density functional.
abstract: In recent papers [A. D. Becke, J. Chem. Phys. 138, 074109 (2013); ibid. 138, 161101 (2013)], a density functional for strong correlations in quantum chemistry was introduced. The functional is designed to capture molecular dissociation limits using symmetry-restricted orbitals. Here we demonstrate that the functional describes, with good accuracy, two-determinant multi-reference states. The examples of this work involve 50∕50 mixing of symmetry-equivalent Slater determinants at avoided crossings. We employ exactly-computed exchange and fractional spin-orbital occupancies. The connection with dissociated systems and single-determinant reference states is explained.
authors.affiliation: Department of Chemistry, Dalhousie University, 6274 Coburg Rd., P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada. axel.becke@dal.ca
authors.forename: Axel D
authors.initials: AD
authors.lastname: Becke