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

## TL;DR

This study uses simplified two-scale potential models to simulate water-alcohol mixtures, successfully reproducing key experimental anomalies and revealing that certain alcohols can enhance water's density maximum behavior.

## Contribution

It introduces a simplified model simulation approach that captures the anomalies of water-alcohol mixtures and demonstrates the structure-making effect of alcohol solutes.

## Key findings

- Qualitative agreement with experimental excess properties
- Alcohol acts as a structure-maker increasing water's density maximum
- Model reproduces anomalies of water-alcohol solutions

## 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.