Can random pinning change the 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 disorder-induced changes in melting scenarios.

Contribution

It demonstrates how quenched disorder from random pinning alters the melting transitions in 2D systems with water-like anomalies, especially transforming first-order transitions into continuous ones.

Findings

Disorder widens the hexatic phase at low densities.

At high densities, pinning converts first-order melting into two separate transitions.

Random pinning induces a KTHNY-like continuous transition at high densities.

Abstract

In experiments the two-dimensional systems are realized mainly on solid substrates which introduce quenched disorder due to some inherent defects. The defects of substrates influence the melting scenario of the systems and have 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 potential in which a small fraction of the particles is pinned, inducing quenched disorder.The potentials of this type are widely used for the qualitative description of the systems with the water-like anomalies. In our previous publications it was shown that the system demonstrates an anomalous melting scenario: at low densities the system melts through two continuous transition in accordance with the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory with the intermediate hexatic phase, while at high densities the conventional first order melting transition takes place. We find that the well-known disorder-induced widening of the hexatic phase occurs at low densities, while at high density part of the phase diagram random pinning transforms the first-order melting into two transitions: the continuous KTHNY-like solid-hexatic transition and first-order hexatic-isotropic liquid transition.