Coupled effect of size, strain rate, and temperature on the shape memory of a pentagonal Cu nanowire

A body-centered pentagonal nanobridge structure with lattice constants c = 2.35 and a = 2.53 angstrom has been observed under high strain rate tensile loading on an initially constrained < 100 >/{100} Cu nanowire at various temperatures. Extensive molecular dynamics (MD) simulations have been performed using the embedded atom method (EAM) for cross-sectional dimensions ranging from 0.723 x 0.723 to 2.169 x 2.169 nm(2), temperature ranging from 10 to 600 K, and strain rates of 10(9)-10(7) s(-1). Formations of such pentagonal nanowire are observed for a temperature range 200-600 K for particular cross-sectional dimensions and strain rates. A large inelastic deformation of similar to 50% is obtained under both isothermal loading and adiabatic loading. With very high degree of repeatability of such pentagonal nanowire formation, the present findings indicate that the interesting stability property and high strength of elongated nanowires have various potential applications in nanomechanical and nanoelectronic devices. Further, we demonstrate a novel thermomechanical unloading mechanism by which it is possible to impart recovery from a pentagonal nanowire following a hysteresis loop: < 100 >/{100} -> pentagonal -> 110/{111} -> < 100 >/{100}.