Energy decomposition in molecular complexes: Implications for the treatment of polarization in molecular simulations

Abstract

This study examines the contribution of electrostatic and polarization to the interaction energy in a variety of molecular complexes. The results obtained from the Kitaura-Morokuma (KM) energy decomposition analysis at the HF/6-31G(d) level indicate that, for intermolecular distances around the equilibrium geometries, the polarization energy can be determined as the addition of the polarization energies of interacting blocks, as the mixed polarization term is typically negligible. Comparison of KM and QM/MM results shows that the electrostatic energy determined in the KM method is underestimated (in absolute value) by QM/MM methods. The reason of such underestimation can be attributed to the simplified representation of treating the interaction between overlapping charge distribution by the interaction of a QM molecule with a set of point charges. Nevertheless, the polarization energies calculated by KM and QM/MM methods are in close agreement. Finally, a consistent, automated strategy to derive charge distributions that include implicitly polarization effects in pairwise, additive force fields is presented. The strategy relies in the simultaneous fitting of electrostatic and polarization energies computed by placing a suitable perturbing particle at selected points around the molecule. The suitability of these charges to describe molecular interactions is discussed.

Calculation of electrostatic interaction energies in molecular dimers from atomic multipole moments obtained by different methods of electron density partitioning

“…Strong exchange repulsion forces (55–133 kJ/mol) are observed in all other dimers, yet the sum of E es and E oi outweighs the repulsion and the total interaction character in these dimers is attractive. These results are in qualitative agreement with the previously performed studies of the energy decomposition in DNA bases69 using Morokuma–Ziegler energy decomposition and with a number of small molecule organic dimers with the Kitaura–Morokuma approach 70. In the first study the reported absolute values of E es , E Pauli , and E oi were smaller and the E es values were consistently closer to E int (within 6–18 kJ/mol) compared to the energies in this study.…”

Analysis of polarization in QM/MM modelling of biologically relevant hydrogen bonds

“…These results can be related to energy decomposition analyses of Curutchet et al (2003). For a set of hydrogen-bonded systems similar to that studied here, they found that, for systems consisting of neutral monomers, the polarization energy amounts to only 10 per cent of the electrostatic energy, but that in cases with charged monomers this proportion rises to approximately 40 per cent.…”

“…Modification of MM atomic charges on neighbouring (bonded) groups is also often recommended (Field et al 1990;Mulholland & Richards 1997). However, no systematic investigation has been performed to find the extent of polarization effects at the QM/MM boundary due to the point charges of MM atoms, except one by Curutchet et al (2003) employing Kitaura-Morokuma ( KM) energy decomposition analysis (Kitaura & Morokuma 1976) at the HF/ 6-31G(d) level for a set of hydrogen-bonded systems.…”

Pair interaction energy decomposition analysis

“…[6][7][8] It also served as a basis to a great number of further improvements and development. [9][10][11][12][13] The original method applied to the analysis of binding between two units (e.g., molecules), and it was extended into a general case of an arbitrary number of units by Chen and Gordon 14 (whose practical implementation was limited to at most 10 units).…”