Structural behavior of a two length scale core-softened fluid in two dimensions

TL;DR

This study uses Langevin Dynamics simulations to explore the complex phase behavior of a two length scale core-softened fluid in two dimensions, revealing three waterlike anomalous regions and their relation to solid phases and re-entrant melting.

Contribution

It uncovers an additional anomalous region in the phase diagram and links it to re-entrant melting and particle conformations, extending previous findings on waterlike anomalies.

Findings

Three anomalous regions identified, including a new one.

Anomalies linked to competition between length scales and particle conformations.

Insights into the relation between solid phases and waterlike anomalies.

Abstract

2D competitive systems shows a large variety of solid and aggregate patterns, re-entrant fluid phase, a continuous melting as predicted by the KTHNY theory and, in some cases, waterlike anomalies. In this paper, we employ Langevin Dynamics simulations of a ramp-like core-softened fluid that have two characteristic length scales and all the features mentioned above. Analyzing the fluid phase of this system, Bordin and Barbosa [Phys. Rev. E 97, 022604 (2018)] reported the existence of two waterlike anomalous region. Now, we revisit this problem focusing in the low temperature regime and a larger range of densities looking for a relation between the origin of the anomalous behavior, the solid phases and the re-entrant melting. Now, not two, but three anomalous regions were observed. The extra anomalous regions are related to the re-entrant melting of a amorphous solid to a cluster fluid. They are ruled not only by the competition between the characteristic length scales in the potential, but also by extra competitions induced by the variety of particles conformations. These competitions extends from the solid to the fluid phase, reflecting in the structural waterlike anomaly. Our results shade some light in the complex behavior of two length scales competitive potential, and helps to elucidate the relation between the large number of solid phases and the existence of more than one waterlike anomalies region in these systems.