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A General Route to Include Pauli Repulsion and Quantum Dispersion Effects in QM/MM Approaches.

Research paper by Tommaso T Giovannini, Piero P Lafiosca, Chiara C Cappelli

Indexed on: 13 Sep '17Published on: 13 Sep '17Published in: Journal of Chemical Theory and Computation



Abstract

A methodology to account for non-electrostatic interactions in Quantum Mechanical (QM)/Molecular Mechanics(MM) approaches is developed. Formulations for Pauli repulsion and dispersion energy, explicitly depending on the QM density are derived. Such expressions are based on the definition of an auxiliary density on the MM portion and the Tkatchenko-Scheffler (TS) approach, respectively. The developed method is general enough to be applied to any QM/MM method and partition, provided an accurate tuning of a small number of parameters is obtained. The coupling of the method with both non-polarizable and the fully polarizable QM/Fluctuating Charges(FQ) approaches is reported and applied. A suitable parametrization for the aqueous solution, so that its most representative features are well reproduced, is outlined. Then, the obtained parametrization and method are applied to calculate the non-electrostatic (repulsion and dispersion) interaction energy of nicotine in aqueous solution.