Dispersion Correction Derived from First Principles for Density Functional Theory and Hartreeâ‹TMFock Theory

The modeling of dispersion interactions in density functional theory (DFT) is commonly performed using an energy correction that involves empirically fitted parameters for all atom pairs of the system investigated. In this study, the first-principles-derived dispersion energy from the effective fragment potential (EFP) method is implemented for the density functional theory (DFT-D(EFP)) and Hartree−Fock (HF-D(EFP)) energies. Overall, DFT-D(EFP) performs similarly to the semiempirical DFT-D corrections for the test cases investigated in this work. HF-D(EFP) tends to underestimate binding energies and overestimate intermolecular equilibrium distances, relative to coupled cluster theory, most likely due to incomplete accounting for electron correlation. Overall, this firstprinciples dispersion correction yields results that are in good agreement with coupledcluster calculations at a low computational cost. ■ INTRODUCTION Intermolecular dispersion forces arise from the interaction between induced multipoles. These forces are at the origin of many chemical and biological processes such as protein folding, molecular recognition, and DNA base pair stacking. The modeling of dispersion interactions has been the subject of many investigations. Density functional theory (DFT) is frequently used to model molecular systems that contain on the order of hundreds of atoms. However, most commonly used density functionals (as well as Hartree− Fock (HF) theory) cannot account for dispersion interactions. Certain density functionals such as MPWB1K, M06-2X, M08-HX, M08-SO, and M11 developed by Truhlar and co-workers correctly capture attractive noncovalent interactions where intermolecular overlap is nonnegligible (at the van der Waals minima). In addition, other functionals such as the van der Waals nonlocal correlation functionals (vdW-DF) include dispersion. In order to enable popular density functionals (GGAs, hybrids, ...) to account for dispersive interactions, Grimme and co-workers introduced a series of empirical corrections, collectively referred to here as “-D”. In DFT-D, the -D dispersion interaction energy correction is added to the Kohn−Sham energy. In general, the dispersion interaction between two molecules A and B can be expressed as