Atom-centered electric multipole moments dynamically generated from QM/MM MD simulations

TL;DR

This paper introduces xDRESP, an extension of the D-RESP method, to compute atom-centered multipoles from QM/MM MD simulations, improving electrostatic modeling and analysis of chemical systems.

Contribution

The paper presents a novel xDRESP method for dynamic multipole generation from QM/MM MD, enhancing electrostatic potential reproduction and chemical system analysis.

Findings

xDRESP outperforms fixed point-charge models in electrostatic potential accuracy.

Atomic multipoles reveal polarization effects and reaction dynamics.

xDRESP serves as an on-the-fly electron density analysis tool.

Abstract

Atom-centered electric multipole moments can be extremely useful in chemistry as they enable the systematic mapping of a complex electrostatic problem to a simpler model. However, since they do not correspond to physical observables, there is no unique way to define them. In this work, we present an extension of the dynamically generated RESP charges (D-RESP) method, referred to as xDRESP, where atom-centered multipoles are computed from mixed quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations. We compare the ability of xDRESP charges to reproduce the electrostatic potential, as well as molecular multipoles, against the performance of fixed point-charge models commonly used in force fields. Moreover, we highlight cases where DRESP atomic multipoles can provide valuable information about chemical systems, such as indicating when polarization plays a significant role, and chemical reactions, in which xDRESP atomic multipoles can be used as an on-the-fly analysis tool to track changes in electron density.