Performance of the AMOEBA Water Model in the Vicinity of QM Solutes: A Diagnosis Using Energy Decomposition Analysis

Abstract

The importance of incorporating solvent polarization effects into the modeling of solvation processes has been well-recognized, and therefore a new generation of hybrid quantum mechanics/molecular mechanics (QM/MM) approaches that accounts for this effect is desirable. We present a fully self-consistent, mutually polarizable QM/MM scheme using the AMOEBA force field, in which the total energy of the system is variationally minimized with respect to both the QM electronic density and the MM induced dipoles. This QM/AMOEBA model is implemented through the Q-Chem/LibEFP code interface and then applied to the evaluation of solute-solvent interaction energies for various systems ranging from the water dimer to neutral and ionic solutes (NH 3 , NH

Computational optimization of electric fields for better catalysis design

“…This is likely why modified Poisson Boltzmann treatments/DFT 58 and classical/quantum DFT approaches 56 and recent hybrid and double hybrid functionals which incorporate some percentage of exact exchange, are addressing better QM accuracy 61 , and new approaches have been introduced that incorporate true many-body polarization effects across the QM/MM boundary. 62,63 This line of research has allowed for accurate rate constant prediction for molecule-surface reactions 64 , while Piccini et al showed how energy barriers for large systems like zeolites (over 1000 atoms) could be calculated within chemical accuracy (within 4 kJ/mol) using Density Functional Theory (DFT) methods. 65 But there are still significant difficulties for metal catalysts, for example metalloenzymes, where there may be multiple reactive sites requiring a QM description 66 , and for which errors in relative free energies do not generally fall below 20 kJ/mol due to poor accounting of strong correlation using DFT 67 .…”

Assessing many-body contributions to intermolecular interactions of the AMOEBA force field using energy decomposition analysis of electronic structure calculations

“…This is probably for the trivial reason that the AMOEBA force field is now imbalanced with the introduction of the new physics that essentially assumes a wholly different charge distribution than the one assumed by Thole damping, and a total reparameterization would have to be undertaken to account for the different charge distribution. Furthermore, it is known that separating the nuclear and electron charges and smearing only the latter makes the issue of the missing exchange effect in polarization more pronounced, 91 which could otherwise curb the overpolarization observed in the short range. The main conclusion from the charge penetration analysis is that we can proceed with the analysis of the AMOEBA polarization against the ALMO-EDA polarization using the original Thole prescription for charge distribution, since the error in the permanent electrostatic field arising from point multipoles does not dominate the polarization errors.…”

A Comparison of QM/MM Simulations with and without the Drude Oscillator Model Based on Hydration Free Energies of Simple Solutes

“…Our recent work [ 133 ] analytically showed that significant additional computational costs can be justified in multi-scale free energy simulations, if the sampling method exhibits a higher phase space overlap with the target QM Hamiltonian. Thus, it can be expected that polarizable force fields and, ultimately, quantum-mechanical methods will play an increasing role in free energy calculations [ 134 , 135 , 136 , 137 , 138 , 139 ].…”