Using ab initio Density Functional Theory total energy calculations, we study the influence of H, B, C, N, O, and S in the rupture of a gold nanowire. In particular, using an as realistic as possible model for a suspended gold nanowire under stress, we observe that the Au wire always break at an Au-Au bond, with a maximum bond length between 3.0 and 3.1 A. Therefore, the experimentally observed large Au-Au bonds before the rupture of the nanowire (≈ 3.6 A) is probably due to the presence of light impurities (X) forming Au-X-Au bonds. We obtain that the Au-Au maximum distance for X equals C or N is of the order of 3.9 A, whereas for B and O it is of the order of 4.1 A. On the other hand, H this maximum distance before the rupture of the wire is approximately 3.6 A, being the best candidate to explain the experimental results. An experimentally observed very large Au-Au bond of 4.8 A is probably caused by an Au-S-Au structure, since we obtain for this configuration an Au-Au distance of ≈4.7 A.
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