How universal is the Lindemann criteria in melting of Lennard-Jones polydisperse solids?

TL;DR

This study investigates the applicability of the Lindemann criterion in melting of polydisperse Lennard-Jones solids through extensive molecular dynamics simulations, revealing size-dependent melting behavior and confirming first-order phase transition at moderate dispersity.

Contribution

It demonstrates that the Lindemann criterion varies with particle size in polydisperse Lennard-Jones solids and confirms first-order melting at moderate dispersity levels.

Findings

Particles of different sizes have different Lindemann ratios at melting.

Melting remains first order at 5-10% size dispersity.

Size dispersion affects the MSD threshold at melting.

Abstract

It is commonly believed that melting occurs when mean square displacement (MSD) of a particle of crystalline solid exceeds a threshold value. This is known as the Lindemann criterion, first introduced in the year of 1910 by Lindemann. However, Chakravarty et al. demonstrated that this common wisdom is inadequate because the MSD at melting can be temperature dependent when pressure is also allowed to vary along the coexistence line of the phase diagram [Chakravarty C, Debenedetti P G and Stillinger F H 2007 J. Chem. Phys.126 204508]. We show here by extensive molecular dynamics simulation of both two and three dimensional polydisperse Lennard-Jones solids that particles on the small and large limits of size distribution exhibit substantially different Lindemann ratio at melting. Despite all the dispersion in MSD, melting is found to be first order in both the dimensions at 5-10% dispersity in size.