Reduced Density Matrix-Driven Complete Active Apace Self-Consistent Field Corrected for Dynamic Correlation from the Adiabatic Connection

摘要

The recently proposed multireference adiabatic connection (AC) formalism [ Pernal , Phys. Rev. Lett. 120 , 013001 (2018)] is applied to recover dynamic electron correlation effects lacking in variational two-electron reduced density matrix (v2RDM)-driven complete active space self-consistent field theory (CASSCF). The AC approach is validated by computing potential energy curves for the dissociation of molecular nitrogen and the symmetric double dissociation of H_(2)O while enforcing two sets of approximate N -representability conditions in the underlying v2RDM-driven CASSCF calculations (either two-particle or two-particle plus partial three-particle conditions). The AC yields smaller absolute errors than second-order N -electron perturbation theory (NEVPT2) at all molecular geometries for both sets of the N -representability conditions considered. The efficacy of the approach for thermochemistry is also assessed for a set of 31 small-molecule reactions. When imposing partial three-particle N -representability conditions, mean and maximum unsigned errors in reaction energies from the AC are superior to those from NEVPT2.