Atomistic modelling of charge-induced deformation of gold nanowires

Experimental studies have shown that electrolyte-emerged nanoporous metals with nano-wire-resembling ligaments as building blocks can undergo considerable dimensional changes when a potential difference is applied. The primary actuation mechanism is the electric double-layer charging of the internal surface. To study the fundamental physical mechanism, we explore the charge-induced deformation of a gold nanowire using atomistic simulations. The excess charge is taken into account by modifying the embedding function of the surface embedded atom method as informed by density functional theory calculations. Our atomistic simulations indicate that the charge-induced deformation increases considerably for reduced cross-sectional dimensions of the wire, and depends sensitively on the crystallographic orientation. We found that anisotropy-driven surface distortions play an important role in transducing the atomistic charge-induced forces into dimensional changes. To capture the fundamental mechanisms, we present a simple analytical model for the charge-induced strain of gold nanowires that is found to be in excellent agreement with the atomistic simulations. (paper)