Molecular modelling and simulation of the surface tension of real quadrupolar fluids

TL;DR

This study uses molecular modelling with force fields to predict the surface tension of 29 real quadrupolar fluids, achieving predictions within about 20% of experimental data, and suggests multi-criteria optimization for improvement.

Contribution

It demonstrates the predictive capability of two-centre Lennard-Jones plus quadrupole models for surface tension of various fluids using only vapor pressure and density data for parameterization.

Findings

Predictions deviate by about 20% from experimental data.

Models tend to overestimate surface tension.

Multi-criteria optimization can improve model accuracy.

Abstract

Molecular modelling and simulation of the surface tension of fluids with force fields is discussed. 29 real fluids are studied, including nitrogen, oxygen, carbon dioxide, carbon monoxide, fluorine, chlorine, bromine, iodine, ethane, ethylene, acetylene, propyne, propylene, propadiene, carbon disulfide, sulfur hexafluoride, and many refrigerants. The fluids are represented by two-centre Lennard-Jones plus point quadrupole models from the literature. These models were adjusted only to experimental data of the vapour pressure and saturated liquid density so that the results for the surface tension are predictions. The deviations between the predictions and experimental data for the surface tension are of the order of 20 percent. The surface tension is usually overestimated by the models. For further improvements, data on the surface tension can be included in the model development. A suitable strategy for this is multi-criteria optimization based on Pareto sets. This is demonstrated using the model for carbon dioxide as an example.