# Molecular dynamics simulations of the properties of water-methanol mixtures. Effects of force fields

## TL;DR

This study uses molecular dynamics simulations to evaluate how different force field combinations predict the structural and thermodynamic properties of water-methanol mixtures, comparing results with experimental data.

## Contribution

It systematically assesses the accuracy of various force field combinations in predicting key properties of water-methanol mixtures.

## Key findings

- Force field choice significantly affects property predictions.
- Simulations accurately reproduce experimental density and surface tension.
- Hydrogen bonding patterns vary with composition and force field.

## Abstract

Isothermal-isobaric molecular dynamics simulations are used to examine the microscopic structure and some properties of water-methanol liquid mixture. The TIP4P/2005 and SPC/E water models are combined with the united atom TraPPE and the all-atom force field model for methanol. Our principal focus is to evaluate the quality of predictions of different combinations of model force fields concerning the composition dependence of basic properties of this system. Specifically, we explored the composition effects on density, excess molar volume and excess entropy, as well as on the surface tension and static dielectric constant. In addition, the structural properties are described in terms of the coordination numbers and the average number of hydrogen bonds between molecules of constituent species. Finally, the composition dependence of self-diffusion coefficients of the species is evaluated. All theoretical predictions are tested with respect to experimental data.