Premelting of thin wires

We have investigated the melting behavior of thin lead wires using molecular dynamics. We find that—in analogy with cluster melting—the melting temperature ${\mathit{T}}_{\mathit{m}}$(R) of a wire with radius R is lower than that of a bulk solid ${\mathit{T}}_{\mathit{m}}^{\mathit{b}}$ by ${\mathit{T}}_{\mathit{m}}$(R)=${\mathit{T}}_{\mathit{m}}^{\mathit{b}}$-c/R. Surface melting effects, with formation of a thin skin of highly diffusive atoms at the wire surface, are observed. The diffusivity is lower over (111)-oriented faces, and higher at (110) and (100) rounded areas. The possible relevance to recent results on nonrupturing thin necks between a scanning tunnel microscope tip and a warm surface is addressed.