Spin-Adapted Formulation and Implementation of Density Cumulant Functional Theory with Density-Fitting Approximation: Application to Transition Metal Compounds.
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.
Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
Xiao
X
Wang
Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
Alexander Yu
AY
Sokolov
Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
Justin M
JM
Turney
Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
Henry F
HF
Schaefer