Diffusion and Relaxation Dynamics in Cluster Crystals

TL;DR

This paper investigates the unique diffusion and relaxation behaviors in cluster crystals formed by ultrasoft particles, revealing hopping mechanisms that enable particle mobility while maintaining crystal structure.

Contribution

It introduces detailed insights into the dynamic mechanisms, such as hopping and decoupling, in cluster crystals with density-independent lattice constants.

Findings

Particles diffuse via activated hopping between lattice sites.

Finite diffusivity and full relaxation of density correlations are observed.

A localization transition is avoided through hopping mechanisms.

Abstract

For a large class of fluids exhibiting ultrasoft bounded pair potentials, particles form crystals consisting of clusters located in the lattice sites, with a density-independent lattice constant. Here we present an investigation on the dynamic features of a representative example of this class. It is found that particles can diffuse between lattice sites, maintaining the lattice structure, through an activated hopping mechanism. This feature yields finite values for the diffusivity and full relaxation of density correlation functions. Simulations suggest the existence of a localization transition which is avoided by hopping, and a dynamic decoupling between self- and collective correlations.