Molecular dynamics simulation of melting of fcc Lennard-Jones nanoparticles

Abstract

Melting of fcc Lennard-Jones (LJ) nanoparticles is studied by heating up models from low temperature toward liquid phase using molecular dynamics (MD) simulation. Atomic mechanism of melting is analyzed via temperature dependence of potential energy, heat capacity, analysis of the spatio-temporal arrangements of liquidlike atoms occurred during the heating process. Moreover, radial distribution function (RDF), mean-squared displacement (MSD) of atoms and radial density profile are also used for deeper analyzing melting. Surface melting is under much attention. We also analyze the evolution of structure of nanoparticles upon heating via the global order parameter Q ₆ and Honeycutt-Andersen (HA) analysis. We find previously unreported information as follows. At temperature far below a melting point, a quasi-liquid layer containing both liquidlike and solidlike atoms occurs in the surface shell of nanoparticles unlike that thought in the past. Further heating leads to the formation of a purely liquid layer at the surface and homogeneous occurrence/growth of liquidlike atoms throughout the interior of nanoparticles. Melting proceeds further via two different mechanisms: homogeneous one in the interior and propagation of liquid front from the surface into the core leading to fast collapse of crystalline matrix.