Melting and Freezing of Au Nanoparticles Confined in Armchair Single-Walled Carbon Nanotubes

Abstract

The structure, phase transition, and nucleation of Au nanoparticles confined within armchair single-walled carbon nanotubes ((n,n)-SWNTs) are investigated using molecular dynamics (MD) simulation technique. The Au−Au interactions are described by the TB-SMA potentials and the Au-SWNT interactions are represented by Lennard-Jones potential. SWNTs are approximately considered to be rigid. The total energies, structures, Lindemman indices, and radial density distributions are used to reveal the feature of phase transition for Au nanoparticles confined in (n,n)-SWNTs. The classical nucleation theory is applied to perform nucleation analysis. Results demonstrate that confined AuN exhibit multishell structures. The order−disorder transformation of atoms in each layer is an important structure feature of phase transition. Interestingly, the melting starts from the innermost layer and freezing starts from outermost layer for confined Au nanoparticles. SWNTs have a significant effect on the structures and stabilities of the confined Au nanoparticles. On the other hand, some important thermodynamic and dynamic parameters are estimated and compared with available experimental and calculated results. This work provides the primary physical insights into the phase transition and nucleation process of confined Au nanoparticles.