Abstract
A recently proposed "DFT + dispersion" treatment (Rajchel et al., Phys. Rev. Lett., 2010, 104, 163001) is described in detail and illustrated by more examples. The formalism derives the dispersion-free density functional theory (DFT) interaction energy and combines it with the dispersion energy from separate DFT calculations. It consists of the self-consistent polarization of DFT monomers restrained by the exclusion principle via the Pauli blockade technique. Within the monomers a complete exchange-correlation potential should be used, but between them only the exact exchange operates. The application to a wide range of molecular complexes from rare-gas dimers to hydrogen-bonds to π-electron interactions shows good agreement with benchmark values.
Highlights
Density Functional Theory (DFT)-based methods provide the most important viable approach to large systems of nano- and biotechnological relevance
Treatment of weak non-covalent interactions by DFT remains plagued by spurious and erratic results. This is a consequence of the fact that stabilization in these complexes is determined by dispersion interaction, not accounted for in standard DFT functionals.[5,6]
In many practical applications remarkable progress has been achieved by using a posteriori dispersion corrections, model and/or semi-empirical, added on the top of regular DFT calculations (DFT+D)[8] in the spirit of the classic SCF+dispersion model of Ahlrichs et al.[14] and Wu et al.[6]
Summary
Density Functional Theory (DFT)-based methods provide the most important viable approach to large systems of nano- and biotechnological relevance. A rigorous approach requires a DFT interaction energy that a priori neglects non-local long-range interaction energy terms (dispersion) but allows for accurate mutual exchange and mutual polarization effects — an analogue of the SCF interaction energy at the DFT level of theory Such a DFT interaction energy could be confidently and rigorously supplemented with a dispersion component obtained at the DFT level of theory using SAPT18,19 or other formalisms.[7,8,16] The goal of this work has been to define an accurate DFT+dispersion treatment which is based the derivation of ”dispersion-free” interaction energy arising between DFT monomers to which a posteriori DFT dispersion energy is added. In Sec III we report numerical results of our method for representative van der Waals and Hbonded systems, and discuss the overall performance of the method
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