Intermolecular dispersion energies from coupled exact-exchange Kohn-Sham excitation energies and vectors

We present two different schemes to reduce the high computational cost for calculating the excitation energies and vectors of the monomers to be used to compute the dispersion energies via the TDDFT method. This is achieved by a decoupling of the occupied-virtual orbital product basis functions which are associated with single-particle excitations belonging to large and small oscillator strengths. It will be shown that this approach can lead to large speedups of 90% and more compared to a full diagonalisation of the hessian, while the fully coupled dispersion energies can be reproduced with a reasonable accuracy. We also investigate the role of the dispersion energy for the description of σ - and π -stacking interactions and discuss various dispersion energy approximations, including the D3 model by Grimme. Graphical abstract

Source: Computational and Theoretical Chemistry - March 2, 2018 Category: Chemistry Source Type: research