Effect of impurities on the breaking of Au nanowires

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 breaks at an Au–Au bond, with a maximum bond length between 3.0 and 3.1 Å. Therefore, the experimentally observed large Au–Au bonds before the rupture of the nanowire (≈3.6 Å) are probably due to the presence of light impurities (X) forming Au–X–Au bonds. We obtain that the maximum Au–Au distance, for X equals C or N, is of the order of 3.9 Å, whereas for B and O it is of the order of 4.1 Å. On the other hand, for H this maximum distance before the rupture of the wire is approximately 3.6 Å, being the best candidate to explain the experimental results. For both C and H impurities, we present a detailed analysis of the neck atoms electronic structures, and compare them with similar results for the pure nanowire.