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

Abstract

Water is an unique material with a long list of thermodynamic, dynamic and structural anomalies, which are usually attributed to the competition between two characteristic length scales in the intermolecular interaction. It has been argued that a potential liquid-liquid phase transition (LLPT) ending at a liquid-liquid critical point (LLCP) lies at the core of the anomalous behavior of water. This transition which has been evidenced in multiple simulation studies seems to be preempted experimentally by spontaneous crystallization. Here, in order to expose the connection between the spontaneous crystallization observed in the supercooled regime in the vicinity of the LLPT, and the density anomaly, we perform extensive Molecular Dynamics simulations of a model mixture of core-softened water and methanol. The pure water-like fluid exhibits a LLPT and a density anomaly. In contrast, our pure methanol-like model does have a LLPT but lacks the density anomaly. Our results illustrate the relation between the vanishing of the density anomaly and an increase in the temperature of the spontaneous crystallization: once this temperature surpasses the LLCP critical temperature, no density anomaly is observed. This peculiar feature illustrates how fine tuning the competitive interactions determine the anomalous behavior of water/alcohol mixtures.

References in corpus (6)

• Glass transition in biomolecules and the liquid-liquid critical point of water
• Water-like hierarchy of anomalies in a continuous spherical shouldered potential
• Free energy surface of ST2 water near the liquid-liquid phase transition
• Structural anomalies for a three dimensional isotropic core-softened potential
• Effects of nanopore and fluid structure on anomalies and phase transitions of confined core-softened fluids
• Molecular dynamics simulations of the properties of water-methanol mixtures. Effects of force fields

Cited by in corpus (5)

• Nanoconfined fluids: Uniqueness of water compared to other liquids
• Core-softened water-alcohol mixtures: the solute-size effects
• Solid-amorphous transition is related to the waterlike anomalies in a fluid without liquid-liquid phase transition
• Density anomaly in water-alcohol mixtures: minimum model for structure makers and breakers
• Phase classification using neural networks: application to supercooled, polymorphic core-softened mixtures