Molecular Dynamics Study of Two-Component Systems:  The Shape and Surface Structure of Water/Ethanol Droplets

Abstract

Molecular dynamics simulations have been performed at T = 260 K on three different sized ethanol/water droplets with a mole fraction of ethanol x = 12%. The calculations were initiated from near spherical configurations taken from simulations of the bulk mixture with the same composition. The results are discussed in comparison to the microphysical models used in nucleation theories. For the droplet having a comparable size to the so-called “critical” cluster, all the ethanol molecules repartition to the surface. The shapes and surface structure of the droplets have been characterized and exhibit increasing fluctuations with decreasing size. These two observations may help explain the present discrepancy between the predicted and calculated rates of nucleation for ethanol/water droplets.

Surfactant Effects and an Order-Disorder Transition in Binary Gas-Liquid Nucleation

“…The density profiles of the critical nuclei at low dimer activities (Fig. 4) resemble those obtained by Tarek and Klein [13] in their molecular dynamics study of waterethanol droplets.…”

Molecular dynamics analysis on wetting and interfacial properties of water-alcohol mixture droplets on a solid surface

“…These mixing rules are used widely in MD simulations, and are applied to water-alcohol mixtures in numerous works. 10,11,[17][18][19] The (111) surface of an fcc crystal consisting of three layers is assumed as the solid wall. The inter-atomic potential between wall particles is expressed by the following harmonic potential for nearest neighbors:…”

“…has not been clearly understood yet, although some preliminary work has been done on investigating water-alcohol mixtures. [10][11][12] In this study, we have performed MD simulations of water-methanol (CH 3 -OH) and water-IPA (isopropylalcohol: (CH 3 ) 2 CH-OH) droplets of various mixture ratios on a solid surface in order to investigate the effects of alcohol additives on droplet wettability. Specific values of each interfacial tension were also investigated by using separate quasione-dimensional systems.…”

Experimental evidence for internal structure in aqueous–organic nanodroplets

“…1,2 Furthermore, the rate at which new particles form is sensitive to the surface free energy, and thus, to the composition and structure of the nanometre sized critical clusters. 3 Evidence for structure in nanodroplets includes the partitioning of ethanol to the surface of ethanol-water clusters in Monte Carlo 3 and molecular dynamics simulations 4 and the scaling with size observed for the organic carbon content in atmospheric aerosols. 5 Direct experimental evidence for a core-shell structure in nanodroplets, however, has been lacking until now.…”