We present a dynamical correlation model for the variational two-electron reduced density matrix (v2RDM) driven complete active space self consistent field (CASSCF) method. The model is based on Pernal’s adiabatic connection (AC) for CASSCF that relies upon transition density matrices derived from an extended random phase approximation (ERPA). The RDMs that enter the ERPA and the AC can be obtained from v2RDM-CASSCF. We validate the AC-v2RDM-CASSCF method by computing potential energy curves for several small molecules. We explore the effects on the AC correlation energy of the N-representability of the RDMs used within the ERPA. We find that the AC-v2RDM-CASSCF recovers most of the dynamical correlation energy missing at the CASSCF level of theory, regardless of whether the RDMs satisfy only two-body or three-body N-representability conditions.

Dynamic correlation model for variational two-electron reduced density matrix driven complete active space self-consistent field methods

2019 Spring National Meeting

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