Dissipative particle dynamics simulations identify structural properties and molecular clustering of alcohol-water mixtures

Abstract

Modeling liquid structures of water and alcohol mixtures via coarse-grained simulations has been a challenge due to the loss of atomistic detail that are required to model the prevailing intermolecular interactions. Moreover, simulating the intrinsic structural ordering and inhomogeneities at mesoscopic-level has also been difficult due to the absence of these interactions. On the other hand, simulating these mixtures at a coarse-grained level is important since these liquids act as solvent in so many different applications. Therefore, in this work we strive to perform coarse-grained dissipative particle dynamics simulations (DPD) to model and simulate alcohol and water liquid mixtures. By using a recently developed DPD parameterization, we characterize their molecular-level structural inhomogeneity by quantifying the molecular clustering. In addition, the results regarding the structure by means of radial distribution functions, three-body angular distributions, and clustering behavior regarding maximum cluster size as a function of distance, cluster distance distribution function clearly show different levels of structural ordering for different mixtures. Moreover, we find that there is a significant difference between alcohol and water clustering behavior. For example, the distance at which clustering occurs in water molecules increases as the concentration of water decreases relative to alcohol. In addition, our results indicate that water and alcohol molecules at different concentrations display inhomogeneity, which agrees well with the literature and all-atom molecular dynamics simulations that are performed within the scope of this work. Hence, the prediction of the structural anomalies in alcohol-water mixtures shows that the employed DPD approach is able to capture the essential molecular structure of water and alcohols. The computational approach can be extended to study other hydrogen bonding soft matter to mimic their experimental structure in complex environments such as biological or synthetic solutions.