  We have studied experimentally the phenomena of jump-to-contact (JC) and
jump-out-of-contact (JOC) in gold electrodes. JC can be observed at the first
contact when the two metals approach each other while JOC occurs in the last
contact before breaking. When the indentation depth between the electrodes is
limited to a certain value of conductance, a highly reproducible behaviour in
the evolution of the conductance can be obtained for hundreds of cycles of
formation and rupture. Molecular dynamics simulations of this process show how
the two metallic electrodes are shaped into tips of a well-defined
crystallographic structure formed through a mechanical annealing mechanism. We
report a detailed analysis of the atomic configurations obtained before contact
and rupture of these stable structures and obtained their conductance using
first-principlesquantum transport calculations. These results help us
understand the values of conductance obtained experimentally in the JC and JOC
phenomena and improve our understanding of atomic-sized contacts and the
evolution of their structural characteristics.
