Effect of impurities on the breaking of Au nanowires Frederico D. Novaes a , E.Z. da Silva b, * , Ant ^ onio J.R. da Silva a,1 , A. Fazzio a,2 a Instituto de F  ısica, USP, CP 66318, 05315-970 Sao Paulo, SP, Brazil b Instituto de F  ısica ‘‘Gleb Wataghin’’, UNICAMP, CP 6165, 13083-970, Campinas, SP, Brazil Available online 19 June 2004 Abstract 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  A. Therefore, the experimentally observed large Au–Au bonds before the rupture of the nanowire (3.6  A) 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  A, whereas for B and O it is of the order of 4.1  A. On the other hand, for H this maximum distance before the rupture of the wire is approximately 3.6  A, 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. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Metallic surfaces; Gold; Computer simulations; Density functional calculations 1. Introduction Metallic nanowires (NWs), and in particular Au nanowires, have been the focus of many recent studies, the main motivations coming from their potential role in nanoelectronics, as well as from a fundamental attempt to understand the behavior of matter as the size of the system approaches the atomic limit. Au NWs show interesting and novel properties, such as quantized conductance, and the ability of evolution into linear gold chains [1–5], which display large, and stable, Au–Au inter- atomic distances before breaking [2,3,6,7]. Whereas the formation and evolution of Au NWs is theoretically well understood [1,8], these large distances have not yet been satisfactorily explained for pure nanowires, despite many at- tempts. The equilibrium Au–Au interatomic dis- tance in the diatomic molecule, is 2.48  A, and in the bulk f.c.c., it is 2.88  A. On Au nanowires under mechanical stress, however, Au–Au distances as large as 3.6–4.0  A have been reported [2]. From a theoretical viewpoint, no one has been able to reproduce the above mentioned large distances for clean NWs, the maximum obtained values being of the order of 3.0–3.1  A, results that are in agree- ment with recent experimental observations [9]. * Corresponding author. Tel.: +55-19-3788-5491; fax: +55- 19-3289-3137. E-mail addresses: zacarias@ifi.unicamp.br (E.Z. da Silva), ajrsilva@if.usp.br (A.J.R. da Silva), fazzio@if.usp.br (A. Faz- zio). 1 Tel.: +55-11-3091-6937; fax: +55-11-3091-6831. 2 Tel.: +55-11-3091-7039; fax: +55-11-3091-6831. 0039-6028/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.susc.2004.06.126 Surface Science 566–568 (2004) 367–371 www.elsevier.com/locate/susc