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

TL;DR

This study models how small amounts of solute affect the temperature of maximum density in water-like mixtures, revealing how solutes can act as structure makers or breakers based on their attraction strength.

Contribution

It introduces a minimal model using a two-length-scale potential to explain the density anomaly behavior in water-alcohol mixtures with varying solute attractions.

Findings

High attraction solutes increase TMD, acting as structure makers.

Low attraction solutes decrease TMD, acting as structure breakers.

The model captures the transition between structure maker and breaker behavior.

Abstract

We modeled the change in the temperature of maximum density (TMD) of a water-like 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 water-like 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.