Towards near-exact solutions of molecular electronic structure: Full coupled-cluster reduction with a second-order perturbative correction

Abstract

We introduce a new augmented adaptation of the recently developed full coupled-cluster reduction (FCCR) with a second-order perturbative correction, abbreviated as FCCR(2). FCCR is a selected coupled-cluster expansion aimed at optimally reducing the excitation manifold and commutator expansions for high-rank excitations to obtain accurate solutions of the electronic Schrodinger equation in a size-extensive manner. The present FCCR(2) enables the estimation of the residual correlation of FCCR by the second-order perturbative correction $E^{(2)}$ from the complementary space of the FCCR projection manifold. The linear relationship between $E^{(2)}$ and the energy of FCCR(2) allows accurate estimates of near-exact energies for a wide variety of molecules with strong electron correlations. The potential of the method is demonstrated using challenging cases, such as the ground state electronic energy of the benzene molecule in equilibrium and stretched geometries, and the isomerization energy of the transition metal complex, [Cu(NH${}_3$)]${}_2$O${}_2$${}^{2+}$.

6 pages, 3 figures, Supporting Information as an ancillary file

References in corpus (3)

• Heat-bath Configuration Interaction: An efficient selected CI algorithm inspired by heat-bath sampling
• Unbiasing the initiator approximation in Full Configuration Interaction Quantum Monte Carlo
• Efficient and Stochastic Multireference Perturbation Theory for Large Active Spaces within a Full Configuration Interaction Quantum Monte Carlo Framework

Cited by in corpus (5)

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• Nonunitary projective transcorrelation theory inspired by the F12 ansatz
• Further Development of iCIPT2 for Strongly Correlated Electrons