Superheating of Ag Nanowires Studied by Molecular Dynamics Simulations

In this work, the superheating of Ag nanowires was studied by molecular dynamics (MD) simulations at the atomic level. The simulation results showed a superheating of about 193 K for Ag nanowires coated by Ni. This is because of the suppression on the melt nucleation and growth due to the epitaxial Ag/Ni interface. These computer experiments reveal a possibility to elevate the instability temperature against melting for nanowires of increasing microelectronic technological interest. Also, a thermodynamic model was constructed to describe the superheating mechanism of the Ag nanowires by considering the Ag/Ni interface free energy. It was found that the nucleation and growth of the melt phase are both suppressed by the low energy Ag/Ni interfaces in Ni-coated Ag wires. The suppression of melt growth is crucial and plays a major role in the process of melting. The thermodynamic analysis gives a quantitative relation of superheating with the Ag wire radius and the contact angle of melting.