Spin-Adapted Formulation and Implementation of Density Cumulant Functional Theory with Density-Fitting Approximation: Application to Transition Metal Compounds

Xiao Wang; Alexander Yu Sokolov; Justin M Turney; Henry F Schaefer

doi:10.1021/acs.jctc.6b00589

Spin-Adapted Formulation and Implementation of Density Cumulant Functional Theory with Density-Fitting Approximation: Application to Transition Metal Compounds

J Chem Theory Comput. 2016 Oct 11;12(10):4833-4842. doi: 10.1021/acs.jctc.6b00589. Epub 2016 Sep 21.

Authors

Xiao Wang¹, Alexander Yu Sokolov², Justin M Turney¹, Henry F Schaefer¹

Affiliations

¹ Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
² Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.

PMID: 27606799
DOI: 10.1021/acs.jctc.6b00589

Abstract

Density cumulant functional theory (DCT) has recently emerged as an attractive ab initio approach for the treatment of electron correlation. In its orbital-optimized formulation (ODC-12) [J. Chem. Phys. 139, 204110 (2013)], DCT has been shown to provide reliable results for a variety of challenging chemical systems. Among the attractive properties of DCT are its size-consistency and size-extensivity, as well as the efficient computation of the molecular properties and analytic gradients. In this work, we present a new formulation and implementation of DCT that takes advantage of spin adaptation and the density-fitting approximation (DF-ODC-12). Our new spin-adapted DF-ODC-12 implementation is more efficient than the previous ODC-12 implementation with up to a ∼12-fold speed-up. We demonstrate the capabilities of DF-ODC-12 with a study of transition metal compounds, which require high levels of electron correlation treatment. For transition metal carbonyl complexes [Fe(CO)₅, Cr(CO)₆] and the ferrocene molecule [Fe(Cp)₂], the DF-ODC-12 equilibrium parameters and bond dissociation energies extrapolated to the complete basis set limit are in very good agreement with reference data derived from experiment.