Reactive Molecular Dynamics Investigation of Toluene Oxidation under Electrostatic Fields: Effect of the Modeling of Local Charge Distribution

Abstract

A reactive Molecular Dynamics (MD) study of toluene oxidation at high temperatures under externally applied electrostatic fields has been performed. The impact of the modeling of local charge distribution has been investigated by comparing the widely used Charge Equilibration (QEq) method with the Charge Transfer with Polarization Current Equalization (QTPIE) method, which shields charge transfers up to atomic orbitals and introduces molecular polarization. Using the latter method, it is possible to improve the computation of the atomic charges, which are a critical aspect for the numerical study of electric fields, and to capture important effects of the electric field on rotational and vibrational energies of the toluene molecule. Results show that a more comprehensive treatment of inter- and intramolecular charge distribution achieved through the QTPIE method leads to substantially different applied forces and oxidation rates of toluene compared to the QEq method. Using the QTPIE method, no significant effects of the electrostatic field on the toluene oxidation rate were observed for the range of temperatures and pressures studied here, which is in disagreement with the results obtained with the QEq method where a clear impact of the electrostatic field on the average oxidation rate was found. Therefore, when studying electric field effects with MD simulations, the choice of the method used for the charge equilibration is a key modeling assumption whose impact should be carefully evaluated.

The role of electric field on decomposition of CL‐20/HMX cocrystal: A reactive molecular dynamics study

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Optimized SQE atomic charges for peptides accessible via a web application

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Water in an External Electric Field: Comparing Charge Distribution Methods Using ReaxFF Simulations

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“…Aside from the QEq studies, a few recent studies apply the charge transfer with polarization current equalization (QTPIE) method to study the effect of an external electric field within the ReaxFF framework. − The QTPIE method is an extension of the QEq method that introduces a charge-transfer cutoff that, in principle, addresses the primary global charge-transfer shortcoming of QEq. The primary drawback of the QTPIE method is that it is formulated based on physical intuition rather than rigorously derived; a distance-dependent function is introduced by which long-range charge transfer is penalized.…”