Revisiting the composition dependence of the properties of water-dimethyl sulfoxide liquid mixtures. Molecular dynamics computer simulations

TL;DR

This study uses molecular dynamics simulations to analyze how the properties of water-DMSO mixtures depend on composition, focusing on structural, thermodynamic, and dynamic properties at room temperature and atmospheric pressure.

Contribution

It systematically evaluates different molecular models for water and DMSO to better understand mixture behaviors and identify potential model improvements.

Findings

Composition-dependent density, enthalpy, and volume trends identified.

Structural analysis reveals changes in hydrogen bonding with composition.

Model evaluations suggest pathways for more accurate simulations.

Abstract

We have revisited the composition dependence of principal properties of liquid water-DMSO mixtures by using the isobaric-isothermal molecular dynamics computer simulations. A set of non-polarizable semi-flexible models for the DMSO molecule combined with the TIP4P-2005 and TIP4P/$\varepsilon$ water models is considered. We restrict calculations to atmospheric pressure, 0.1013 MPa, and room temperature, 298.15 K. Composition trends of density, excess mixing volume and excess mixing enthalpy, partial molar volumes and partial molar enthalpies of species, apparent molar volumes are reported. Besides, we explore composition trends of the self-diffusion of species, the static dielectric constant and the surface tension. Evolution of the microscopic structure of the mixture with composition is analyzed in terms of radial distributions functions, coordination numbers and the fractions of hydrogen-bonded molecules. We intend to capture the peculiarities of mixing the species in the mixture upon the DMSO molar fraction and the anomalous behaviors, if manifested in each of the properties under study. The quality of several combinations of the models for species is evaluated in detail to establish the possibility of necessary improvements.