Molecular dynamics study of melting properties of gold nanorods

The melting properties of gold nanorods (AuNRs) are investigated by means of molecular dynamics simulations based on the Embedded-Atom-Method (EAM) potential. The diameters and lengths of the AuNRs are varied from 2.03 nm to 9.44 nm and from 19.43 nm to 93.04 nm, respectively. The premelting of AuNRs is characterized by studying the variation of the Lindemann index with temperature. The simulation results revealed that the melting of AuNR surface is an inhomogeneous, gradually occurring process. This behavior is discussed in the context of the surface atoms of AuNRs requiring different energy values to lose the solid ordering resulting from the fact that they are in contact with irregular number of nearest-neighbors. Furthermore, the ratio between the premelting temperature (Tsm) and melting temperature (Tpm) of the AuNR (also called premelting ratio (Tsm/Tpm)) is calculated for all sizes to provide a new insight into the size dependence of the premelting phenomenon. It is found that the AuNR premelting ratio increases as NP size decreases, thus suggesting that the premelting phenomenon is less pronounced in the smallest NPs.