Size-dependent multilayer relaxation of nanowires and additional effect of surface stresses

A theoretical investigation was carried out on multilayer relaxation, surface energy and surface stress in [001] oriented rectangular f.c.c metal nanowires using the modified embedded atom method. Surprisingly, the multilayer relaxation behavior depends on the wire sizes in absolutely distinct trends for inward-relaxation metals Ag, Cu, and for outward-relaxation metals Ir and Ni. Specifically, the outmost interlayer relaxation |Δd12| increases with decreasing cross-section areas for Ag, Cu nanowires, while it decreases for Ir, Ni nanowires. This is due to the additional effect of surface stress, which, with the surface energy, increases with decreasing wire width monotonically.