Premelting of Thin Wires

TL;DR

This study investigates the melting behavior of thin cylindrical lead wires, revealing size-dependent melting temperatures, surface melting effects, and atom diffusion variations, with implications for nanoscale metallic structures.

Contribution

It introduces a molecular dynamics analysis of thin wire melting, highlighting size effects and surface phenomena not previously detailed.

Findings

Melting temperature decreases with wire radius, following T_m(R) = T_m^b - c/R.

Surface melting involves a diffusive skin of atoms at the wire surface.

Diffusivity varies with surface orientation, being lower at flat (111) surfaces.

Abstract

Recent work has raised considerable interest on the nature of thin metallic wires. We have investigated the melting behavior of thin cylindrical Pb wires with the axis along a (110) direction, using molecular dynamics and a well-tested many-body potential. We find that---in analogy with cluster melting---the melting temperature $T_m (R)$ of a wire with radius $R$ is lower than that of a bulk solid, $T_m^b$, by $T_m (R) = T_m^b -c/R$. Surface melting effects, with formation of a thin skin of highly diffusive atoms at the wire surface, is observed. The diffusivity is lower where the wire surface has a flat, local (111) orientation, and higher at (110) and (100) rounded areas. The possible relevance to recent results on non-rupturing thin necks between an STM tip and a warm surface is addressed.