Melting behaviour of a pentagonal Au nanotube

Molecular dynamics simulations have been employed to investigate the melting behaviour of an Au nanotube with pentagonal symmetry. The hollow pentagonal prism consists of five crystalline domains with (100) facets separated by grain boundaries. The atoms located at the edges, at the free surfaces, at the grain boundaries and in the bulk of the nanotube have different structural arrangement and therefore different thermal stability. A sequence of pre-melting transitions takes place progressively involving edges, surfaces and grain boundaries. Within a narrow temperature range, the molten phase forms a connected three-dimensional diffusion path permitting the exchange of atoms between external and internal surfaces. Bulk atoms finally melt at a temperature significantly lower than the equilibrium melting point.