Prediction of enthalpy of vaporization for particulate matter through molecular dynamics using OPLS force field

Abstract

Chemical pollutant molecules dispersed in the atmosphere in the form of particulate matter are harmful to humans. Accurate data sets on the volatility of particulate matter components are required to address the ongoing issues of air pollution, as volatility determines the distribution of particulate components between gas and particle phases. Herein, we estimate the volatility for representative components of particulate matter by calculating the enthalpy of vaporization using molecular dynamics simulations. Compared with conventional static prediction methods such as Hansen solubility parameter and conductor-like screening model methods, the molecular dynamics method proves to effectively and accurately predict enthalpies of vaporization for a wide range of particulate matter components without additional parameter optimization. Using the molecular dynamics approach, we calculate enthalpies of vaporization for 71 representative organic species that could be primary particulate matter sources. The predicted enthalpy of vaporization values can be used as a fundamental data set for future air quality modeling and scientific understanding of the formation of particulate matter. Given the limitations in experimentally characterizing the volatility of various components in particulate matter, we envisage that our dynamical method based on the evaluation of intermolecular interactions can also be used to study the dynamics associated with the formation of particulate matter in addition to providing thermodynamic data.