  Many experiments have shown that the conductance histograms of metallic
atomic-sized contacts exhibit a peak structure, which is characteristic of the
corresponding material. The origin of these peaks still remains as an open
problem. In order to shed some light on this issue, we present a theoretical
analysis of the conductance histograms of Au atomic contacts. We have combined
classical molecular dynamics simulations of the breaking of nanocontacts with
conductance calculations based on a tight-binding model. This combination gives
us access to crucial information such as contact geometries, forces, minimum
cross-section, total conductance and transmission coefficients of the
individual conduction channels. The ensemble of our results suggests that the
low temperature Au conductance histograms are a consequence of a subtle
interplay between mechanical and electrical properties of these nanocontacts.
At variance with other suggestions in the literature, our results indicate that
the peaks in the Au conductance histograms are not a simple consequence of
conductance quantization or the existence of exceptionally stable radii. We
show that the main peak in the histogram close to one quantum of conductance is
due to the formation of single-atom contacts and chains of gold atoms.
Moreover, we present a detailed comparison with experimental results on Au
atomic contacts where the individual channel transmissions have been
determined.
