A classical reactive potential for molecular clusters of sulphuric acid and water

TL;DR

This paper introduces a two-state empirical valence bond potential for modeling sulphuric acid-water interactions, enabling classical simulations of proton transfer relevant to atmospheric aerosol formation.

Contribution

It develops and parametrizes a new EVB potential for sulphuric acid and water clusters, validated against DFT data, to study proton transfer in atmospheric aerosols.

Findings

A single sulphuric acid molecule donates a proton when clustered with four water molecules at 300 K.

The EVB model shows good agreement with DFT calculations.

Proton transfer threshold depends on temperature.

Abstract

We present a two-state empirical valence bond (EVB) potential describing interactions between sulphuric acid and water molecules and designed to model proton transfer between them within a classical dynamical framework. The potential has been developed in order to study the properties of molecular clusters of these species, which are thought to be relevant to atmospheric aerosol nucleation. The particle swarm optimisation method has been used to fit the parameters of the EVB model to density functional theory (DFT) calculations. Features of the parametrised model and DFT data are compared and found to be in satisfactory agreement. In particular, it is found that a single sulphuric acid molecule will donate a proton when clustered with four water molecules at 300 K and that this threshold is temperature dependent.