Hexatic phase in the two-dimensional Gaussian-core model

TL;DR

This study uses Monte Carlo simulations to explore the phase behavior of 2D particles with Gaussian repulsion, revealing a continuous melting transition with an intermediate hexatic phase consistent with Kosterlitz-Thouless theory.

Contribution

It demonstrates the existence of a hexatic phase and continuous melting in the 2D Gaussian-core model, extending understanding of phase transitions in soft-core particle systems.

Findings

Reentrant melting transition observed upon compression.

Presence of a stable hexatic phase during melting.

Evidence supports the Kosterlitz-Thouless-Halperin-Nelson-Young scenario.

Abstract

We present a Monte Carlo simulation study of the phase behavior of two-dimensional classical particles repelling each other through an isotropic Gaussian potential. As in the analogous three-dimensional case, a reentrant-melting transition occurs upon compression for not too high temperatures, along with a spectrum of water-like anomalies in the fluid phase. However, in two dimensions melting is a continuous two-stage transition, with an intermediate hexatic phase which becomes increasingly more definite as pressure grows. All available evidence supports the Kosterlitz-Thouless-Halperin-Nelson-Young scenario for this melting transition. We expect that such a phenomenology can be checked in confined monolayers of charge-stabilized colloids with a softened core.