(659e) Formation of Polyhedral Structures in Elongated Gold Nanowires

The break structures formed by metallic nanowires under elongation have important implications in the areas of molecular- and nano-electronics. In particular, the observations of quantized conductance in single-atom wide break junctions has fueled much interest into understanding the underlying mechanisms. Gold nanowires have been demonstrated to form single-atom wide and helical chains when stretched. The temperature and rate of elongation strongly dictate the length of these chains, e.g. long chains are favored for low temperature systems with fast elongation rates [1]. Most of the previous work on gold nanowires has focused on the crystalline nature of the wire, however non-crystalline configurations may have important implications regarding the structural pathway and transport properties; for example, icosahedral structures have been observed in sodium nanowires under elongation [2]. In this work, we use molecular dynamics simulations of gold nanowires that utilize the tight-binding second-moment approximation potential (TB-SMA) to explore the elongation behavior of gold nanowires. We observe the widespread formation of polyhedral Z12 (i.e icosahedron) and Z14 structures and quantify their presence using the Rylm method based on spherical harmonics [3]. We propose that the formation of polyhedral structures is important to the elongation pathway, in particular, important to the formation of single-atom wide chains.

[1] Pu Q, Leng YS, Cummings PT, Rate-Dependent Energy Release Mechanism of Gold Nanowires under Elongation, JACS 130 (52), 2008

[2] R. Barnett and U. Landman, Cluster-derived structures and conductance fluctuations in nanowires, Nature 387, 788 (1997)

[3] Iacovella CR, Keys AS, Horsch MA, Glotzer SC, Icosahedral packing of polymer-tethered nanospheres and stabilization of the gyroid phase, PRE 75(4), 2007