Melting of a two-dimensional monodisperse cluster crystal to a cluster liquid.

Wang, Wenlong; Díaz-Méndez, Rogelio; Wallin, Mats; Lidmar, Jack; Babaev, Egor · Phys Rev E · 2019

basic_science · Level V

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Abstract

Monodisperse ensembles of particles that have cluster crystalline phases at low temperatures can model a number of physical systems, such as vortices in type-1.5 superconductors, colloidal suspensions, and cold atoms. In this work, we study a two-dimensional cluster-forming particle system interacting via an ultrasoft potential. We present a simple mean-field characterization of the cluster-crystal ground state, corroborating with Monte Carlo simulations for a wide range of densities. The efficiency of several Monte Carlo algorithms is compared, and the challenges of thermal equilibrium sampling are identified. We demonstrate that the liquid to cluster-crystal phase transition is of first order and occurs in a single step, and the liquid phase is a cluster liquid.