Dimension-induced structural stability transition: The stable and metastable phases of nanowires

The energy along the epitaxial Bain paths (EBP's) was calculated for [001] oriented rectangular Ag, Cu, Ni nanowires as well as for bulk crystals using the second-nearest-neighbor modified embedded atom method (2NN-MEAM). Interestingly, it seemed that the stable phases (c/a=1) and metastable phases (c/a≈0.6) of bulk crystals exchanged with each other when the wire width was reduced down to about several atom layers. The fct lattice with c/a≈0.6, which cannot exist stably in bulk form, becomes possible in this dimension scale. During the top-down preparation processes, nanowires may transform from the metastable phases to the stable phases spontaneously driven by surface effect.