Temperature of maximum density and excess properties of short-chain alcohol aqueous solutions: A simplified model simulation study

Abstract

We perform an extensive computational study of binary mixtures of water and short-chain alcohols resorting to two-scale potential models to account for the singularities of hydrogen bonded liquids. Water molecules are represented by a well studied core softened potential which is known to qualitatively account for a large number of water's characteristic anomalies. Along the same lines, alcohol molecules are idealized by dimers in which the hydroxyl groups interact with each other and with water with a core softened potential as well. Interactions involving non-polar groups are all deemed purely repulsive. We find that the qualitative behavior of excess properties (excess volume, enthalpy and constant pressure heat capacity) agrees with that found experimentally for alcohols such as t-butanol in water. Moreover, we observe that our simple solute under certain conditions acts as an "structure-maker", in the sense that the temperature of maximum density of the bulk water model increases as the solute is added, i.e. the anomalous behavior of the solvent is enhanced by the solute. PACS numbers:1 arXiv:1701.08670v1 [cond-mat.soft]

Modeling the temperature of maximum density of aqueous tert-butanol solutions

“…In contrast, another two-length scale potential dimer model proposed in Ref. [36] displayed a behavior in accordance with the experimental data, but for artificially low densities. On the other hand, atomistic simulations using either united atom models OPLS for methanol [35], or the very recent simulation work for alcohol/water solutions using flexible all-atom models for methanol, ethanol, propanol, and tert-butanol together with TIP4P/2005f water [37], all fail to reproduce the enhancement of the density anomaly for small alcohol concentrations.…”

“…Since the original contributions of Wada and Umeda in the early sixties [19,20], a number of works have addressed the issue of the solute's influence on the TMD of water in the case of short chain alcohols [29][30][31][32][33][34][35][36]. Among these, it is worth mentioning the statistical me- mental data [38] and Kusalik models.…”

Competing interactions near the liquid-liquid phase transition of core-softened water/methanol mixtures

“…We have first analyzed the behavior of the temperature of maximum density (TMD) [62]. Previous studies using a different core-softened model [76] lead to TMDs appearing at too low temperatures and densities. For the methanol geometry, in Ref.…”

“…The competition between microscopic water structures induced by the first or the second length scale is directly related to the presence of anomalies -as the competition between two fluids structures in liquid water [41]. More recently, this core-softened approach has been extended to methanol [73,74] and water-metanol mixtures [75,76]. In these models the methanol is modeled as a dumbbell, with a CS site as the hydroxyl-like monomer and a standard Lennard-Jones (LJ) site as the methyllike monomer.…”

Phase classification using neural networks: application to supercooled, polymorphic core-softened mixtures

“…The motivation behind the studies of these particular systems lays on their wide range of application such as dispersion media [56], disinfectant [57], in the food [58] and medical [59] industries, among others. Many experimental and theoretical works have studied these short-chain alcohol/water mixtures [60,61,62,63,64,65,66]. In our recent works, we have performed Molecular Dynamics (MD) simulations with a coresoftened (CS) approach to investigate the behavior of methanol-water [67] and water mixtures with methanol, ethanol and 1-propanol [68].…”