A Computationally Feasible DFT/CCSD(T) Correction Scheme for the Description of Weakly Interacting Systems

A computationally feasible DFT/CCSD(T) correction scheme is proposed for precise calculations (close to the CCSD(T) accuracy) of weakly interacting molecular clusters. This approach formally falls within the DFTD class of methods (empirically corrected DFT methods), however, there are several important differences between the DFT/CCSD(T) scheme proposed here and a standard DFTD approach: (i) it is parameter free, (ii) it does not use any damping functions, and (iii) the error of DFT is assumed to be anisotropic in general. In addition, the proposed DFT/CCSD(T) correction scheme allows the analysis of assumptions commonly used in the DFTD calculations. Application of this method on the ethylene-benzene and benzene-benzene complexes leads to the conclusion that interaction energies obtained with the DFT/CCSD(T) correction scheme can be obtained with a near reference level accuracy with an error not exceeding 0.1 kcal/mol. A proper choice of a reference set is shown to be more important than the anisotropy of the DFT/CCSD(T) correction.