Conductance and Mechanical Properties of Atomic-Size Metallic Contacts: A Simple Model

We present a simple model for the evolution of atomic-scale metallic contacts together with exact free-electron calculations of the conductance during an elongation-contraction process. The critical pressure that the neck can sustain before yielding is constant. Shortly before the neck breaks the pressure gradually increases up to a maximum for a single-atom contact. In force microscopy experiments this maximum value also depends on the cantilever constant. Conductance histograms show clear peaks at integer multiples of 2e²/h slightly shifted to lower values.