Density functionals for static, dynamical, and strong correlation

In this work, our exact-exchange-based static + dynamical correlation density functional [A. D. Becke, J. Chem. Phys. 122, 064101 (2005)]10.1063/1.1844493 is generalized to include “strong” correlation, i.e., accurate computations on dissociating chemical systems without breaking space or spin symmetries and without using multi-determinantal reference states. Also, we introduce a strong-correlation benchmark set composed of space- and spin-symmetrized open-shell atoms on which the generalized functional is tested. Initial results are very promising.