A comparative study of aqueous DMSO mixtures by computer simulations and integral equation theories

TL;DR

This study compares computer simulations and integral equation theories to understand water-DMSO mixtures, highlighting the importance of water bridge diagrams and analyzing the ability of theories to replicate experimental and simulation features.

Contribution

It demonstrates the necessity of including water bridge diagrams in integral equation theories to accurately reproduce water-water correlations in aqueous DMSO mixtures.

Findings

Integral equation theories require water bridge diagrams for accurate correlation reproduction.

Theories poorly reproduce atom-atom distribution functions but match Kirkwood-Buff integrals.

X-ray scattering data does not show the cluster pre-peak observed in simulations.

Abstract

Several computer simulation studies of aqueous dimethylsulfoxyde with different force field models, and conducted by different authors, point out to an anomalous depressing of second and third neighbour correlations of the water-water radial distribution functions. This seemingly universal feature can be interpreted as the formation of linear water clusters. We test here the ability of liquid state integral equation theories to reproduce this feature. It is found that the incorporation of the water bridge diagram function is required to reproduce this feature. These theories are generally unable to properly reproduce atom-atom distribution functions. However, the near-ideal Kirkwood-Buff integrals are relatively well reproduced. We compute the Xray scattering function and compare with available experimental results, with the particular focus to explain why this data does not reproduce the cluster pre-peak observed in the water-water structure factor.