Size-dependent structural phase transition of face-centered-cubic metal nanowires

Taking Au as an example, we have investigated the epitaxial bain paths of (001) oriented face-centered-cubic metal nanowires. It demonstrates that there are one stable and one metastable phase, having the lattice constant ratio c/a of about 0.6 and 1.0, respectively. Even without any external stimuli, the surface-tension-induced intrinsic stress in the interior may drive the nanowires to phase transform spontaneously for surface-energy minimization. However, this structural transition depends on the feature sizes of the nanowires. Specifically, only when the cross-section areas are reduced to 4.147 nm² or so can the surface energy and the intrinsic stress satisfy the thermodynamic and kinetic conditions simultaneously.