Phase diagram and water-like anomalies in core-softened shoulder-dumbbells system

TL;DR

This study uses molecular dynamics to explore how anisotropy in core-softened shoulder-dumbbells affects phase boundaries and water-like anomalies, revealing that small anisotropy enlarges anomalous regions while larger anisotropy shrinks them.

Contribution

It demonstrates that small anisotropy increases anomalous regions in the phase diagram, and introduces a kinetic energy decoupling approach to understand this behavior.

Findings

Small anisotropy enlarges anomalous regions.

Large anisotropy reduces anomalous regions.

Decoupling kinetic energies explains the anomaly behavior.

Abstract

Using molecular dynamics we studied the role of the anisotropy on the phase boundary and on the anomalous behavior of 250 dimeric particles interacting by a core-softened potential. This study led us to an unexpected result: the introduction of a rather small anisotropy, quantified by the distance between the particles inside each dimer, leads to the increase of the size of the regions in the pressure-temperature phase diagram of anomalies when compared to the isotropic monomeric case. However, as the anisotropy increases beyond a threshold the anomalous regions shrinks. We found that this behavior can be understood by decoupling the translational and non-translational kinetic energy components into different translational and non-translational temperatures.