Molecular Dynamics Study of Melting of Nano Aluminum Particles

Abstract

Molecular dynamics simulations are performed using isobaric-isoenthalpic (NPH) ensembles to predict the melting of nano-sized aluminum particles in the range of 2-9 nm and to investigate the effect of charge development on the melting. Five different potential functions (i.e., the Lennard-Jones, Glue, Embedded Atom, Streitz-Mintmire, and SuttonChen potentials are employed, and the results are compared using the size dependence of melting phenomenon as a benchmark. A combination of structural and thermodynamic parameters such as the potential energy, Lindemann index, translational-order parameter, and radial-distribution functions are employed to characterize the melting process. Both bulk and particle melting are considered. The former is characterized by a sharp increase in structural and thermodynamic properties, whereas the latter involves surface pre-melting. The effect of surface charges on the melting point is found to be insignificant for nano-sized aluminum particles. The melting point of a nano particle increases monotonically with increasing size and approaches the bulk melting point at approximately 8 nm. Two-body potentials like the Lennard-Jones potential fail to capture the thermodynamic melting phenomenon. The Sutton-Chen potential, fitted to match structural properties, also fails to capture the size dependence of the particle melting point. Many-body potentials like the Glue and Streitz-Mintmire potentials result in accurate melting temperature as a function of particle size.