Influence of random pinning on melting scenario of two-dimensional core-softened potential system

TL;DR

This study uses molecular dynamics simulations to explore how random pinning affects the melting behavior of a two-dimensional core-softened potential system, revealing that disorder can alter transition types but not the overall melting scenario.

Contribution

It demonstrates that quenched disorder from random pinning can modify the melting transitions in 2D core-softened systems, especially transforming single first-order transitions into multiple transitions.

Findings

Random pinning widens the hexatic phase.

In systems with larger repulsive steps, disorder changes a single first-order transition into two separate transitions.

The overall melting scenario remains consistent despite the presence of disorder.

Abstract

The random disorder can drastically change the melting scenario of two-dimensional systems and has to be taken into account in the interpretation of the experimental results. We present the results of the molecular dynamics simulations of the two dimensional system with the core-softened potentials with two repulsive steps in which a small fraction of the particles is pinned, inducing quenched disorder. It is shown that without the quenched disorder the system with small repulsive shoulder, which is close in the shape to the soft disks, melts in accordance with the melting scenario proposed in Refs. [30,31,33] (first-order liquid-hexatic and continuous hexatic-solid transitions). Random pinning widens the hexatic phase, but leaves the melting scenario unchanged. For the system with larger repulsive step at high densities the conventional first-order transition takes place without random pinning. However, in the presence of disorder the single first-order transition transforms into two transitions, one of them (solid-hexatic) is the continuous KTHNY-like transition, while the hexatic to isotropic liquid transition occurs as the first order transition.