On the Melting and Freezing of Au-Pt Nanoparticles Confined in Single-Walled Carbon Nanotubes

A MD simulation method is used to simulate the melting and freezing of Au-Pt nanoparticles confined in armchair single-walled carbon tubes ((n,n)-SWNTs), applying the second-moment approximation of the tight-binding potentials for metal metal interactions and Lennard-Jones potential for the metal carbon interactions. The carbon atoms on the SWNTs are taken to be fixed. The structures, total energies, Lindemman indices, and radial and axial density distributions are used to examine the behaviors of melting and freezing for Au-Pt nanoparticles confined in (n,n)-SWNTs. The nucleation analysis is carried out in terms of classical nucleation theory. The simulation results demonstrate that the solid Au-Pt dusters confined within (n,n)-SWNTs have multishell structures, even in a melted cluster. In addition, for the confined Au-Pt nanoparticles, Pt atoms tend to stay at the position close to the SWNT wall, which is different from free Au-Pt nanoparticles. Simulation results reveal that SWNTs and compositions of nanoparticles have significant effects on the structures and physical properties of the confined Au-Pt nanoparticles. On the other hand, some important thermodynamic and dynamic parameters are estimated based on MD simulations and compared with available theoretical and experimental results.