Ab initio study of evolution of mechanical and transport properties of clean and contaminated Au nanowires along the deformation path

We present a first-principles study of the evolution of the mechanical and transport properties of clean and contaminated Au nanowires during the whole breaking process. We combine density functional theory total energy calculations and Keldysh Green's function methods in order to determine the changes in the structure and conductance induced by the presence of hydrogen and oxygen atomic impurities. Our simulations show how atomic oxygen is incorporated into the nanowire, forming long monoatomic chains, in good agreement with the experimental observation. The presence of adsorbed atomic impurities introduces significant changes in the conductance, providing a quantitative explanation for the new peaks found in the conductance histograms recorded in the presence of the corresponding molecular species. The exothermic character of the dissociation process in the nanowire found in our study provides a sound basis for the presence of these atomic impurities, although the problem of finding a low-activation energy path for the oxygen molecule remains open. This enhanced chemical reactivity can be traced back, through the analysis of the local density of states, to both the reduced coordination and the applied tensile strain.