Electrostatic energy in the effective fragment potential method: Theory and application to benzene dimer

Abstract

Evaluation of the electrostatic energy within the effective fragment potential (EFP) method is presented.The performance of two variants of the distributed multipole analysis (DMA) together with two different models for estimating the charge penetration energies was studied using six homonuclear dimers. The importance of damping the higher order multipole terms, i.e. charge dipole, was also investigated. Damping corrections recover more than 70% of the charge penetration energy in all dimers, whereas higher order damping introduces only minor improvement. Electrostatic energies calculated by the numerical DMA are less accurate than those calculated by the analytic DMA. Analysis of bonding in the benzene dimer shows that EFP with inclusion of the electrostatic damping term performs very well compared to the high-level coupled cluster singles, doubles, and perturbative triples method. The largest error of 0.4 kcal/mol occurs for the sandwich dimer configuration. This error is about half the size of the corresponding error in second order perturbation theory. Thus, EFP in the current implementation is an accurate and computationally inexpensive method for calculating interaction energies in weakly bonded molecular complexes.

Modeling π–π Interactions with the Effective Fragment Potential Method: The Benzene Dimer and Substituents

“…45 Distributed multipoles on atoms and bond midpoints were generated using a numerical integration scheme. 48 The electrostatic charge-charge, charge-dipole, charge-quadrupole, and dipole-dipole energies were screened by charge-penetration damping functions, as described in ref 48.…”

“…Recently, EFP2 was shown to successfully model the π-π interactions in the unsubstituted benzene dimer. 48 An EFP2 study of benzene-water complexes is in progress. 58 The main goal of the present work is to further investigate the performance of EFP2 for systems with π-π interactions, to confidently model various biological systems (e.g., interactions in DNA base pairs) in future studies.…”

Coarse-Grained Intermolecular Potentials Derived From The Effective Fragment Potential: Application To Water, Benzene, And Carbon Tetrachloride

“…Thus, electrostatic interactions become too repulsive whereas the induction energy is too attractive if fragments approach each other too closely. In order to avoid this unphysical behavior, electrostatic and induction energy terms are modulated by exponential damping functions with parameters being obtained from fitting the damped multipole potential to the Hartree-Fock one [41,42]. In EFP2, the induction energy terms are damped in a similar way [43].…”

“…For example, calculation of the energy and gradient for a system of 64 waters with periodic boundary conditions (PBC) requires about 2 s on one Opteron 2600 MHz processor. Despite its low computational cost, the accuracy of EFP in predicting structures and binding energies in weakly-bonded complexes and liquids is very high and comparable with that of MP2 [42].…”

“…Compared to experiment, the EFP2 RDF features are slightly more pronounced, suggesting that EFP2 over-structures liquid benzene. This may be due to the fact that EFP2 slightly overestimates the interactions between benzene molecules [42]. The EFP1/MP2 oxygen-oxygen RDF for water is shown in Figure 8-6.…”