Density anomaly in water-alcohol mixtures: Minimum model for structure makers and breakers

Abstract

We modeled the change in the temperature of maximum density (TMD) of a waterlike solvent when small amounts of solute are added to the mixture. The solvent is modeled as a two length scales potential, which is known to exhibit waterlike characteristic anomalies, while the solute is chosen to have an attractive interaction with the solvent which is tuned from small to large attractive potential. We show that if the solute exhibits high attraction with the solvent it behaves as a structure maker and the TMD increases with the addition of solute, while if the solute shows a low attraction with the solvent the TMD decreases, with the solute behaving as a structure breaker.

The temperature of maximum density for aqueous solutions

“…The effect of non-polar solutes over TMD has also been studied using molecular simulation. Habitzreuter and Barbosa 16 modeled water with a softened-core potential with two length scales and the non-polar solute with the Lennard-Jones potential. Solute-solute interactions were represented by the Weeks-Chandler-Andersen potential.…”

“…Using these computational tools, a detailed study of the effect of the solutes in the water structure could be carried out, allowing reaching to deeper and more rigorous conclusions about the microscopic origins underlying the TMD behavior. [16][17][18][19] In this Perspective, we show the theoretical thermodynamic framework that relates TMD to other physical properties, we summarize the experimental data of TMD for a wide class of solutes, and we try to expose the most significant results, mainly based on molecular simulation data, that link the TMD behavior with changes in the water structure. Finally, the main conclusions about the TMD work over the years are drawn out, and future researching lines for a better understanding of TMD are proposed.…”