The role of carbon contamination in metallic nanowires

metallic nanowires have attracted much attention in the last years due to new phenomena such as quantum conductance and the existence of unexpected long interatomic distances attaining 0.3-0.5 nm. these large distances represented a challenge for physical interpretation. in this work we present experimental data from high-resolution transmission electron microscopy and results from ab initio calculations for suspended gold chains and show that these large distances can be easily explained by the presence of carbon atoms as contaminants. in principle the present conclusions can be also applied to other metallic nanowires (such as ag and pt) whose structures also present large interatomic distances.