ABSTRACT
: We have studied experimentally jump-to-contact (JC) and jump-out-of-contact (JOC) phenomena in gold electrodes. JC can be observed at first contact when 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-principles quantum 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.
ABSTRACT
Molecular dynamics simulations of fused silica at shock pressures reproduce the experimental equation of state of this material and explain its characteristic shape. We demonstrate that shock waves modify the medium-range order of this amorphous system, producing changes that are only clearly revealed by its ring size distribution. The ring size distribution remains practically unchanged during elastic compression but varies continuously after the transition to the plastic regime.
