Atomic and multi-scale modeling of non-equilibrium dynamics at metal–metal contacts

摘要

A coarse graining method that introduces Joule heating and improves heat transport in a classical molecular dynamics simulation is reviewed, and two example sets of simulations, opening of gold–gold nano-asperity contacts and nano-asperity sliding at loaded copper–aluminum interfaces are discussed. For the gold contact, dislocations nucleate from the edges of where the asperity contacts the substrates and move along the close-packed planes, resulting in stacking faults that form two subsurface Thompson tetrahedra. For a nullvoltage, a nanowire with a diameter much smaller than the initial contact area is created when the two tetrahedra are completed, and as the wire yieldsthe partial dislocations retreat to the surface. Opening with Joule heating enhances dislocation mobility and intransient subsurface plasticity. Constant current simulations show melting and boiling of the nanowires depending on the voltage cap. Sliding of an aluminum asperity on copper with a null voltage shows dislocation formation in the copper and aluminum, while heating from an applied voltage eliminates damage in the copper. Sliding with a copper asperity enhances plastic damage in the copper substrate compared with the aluminum asperity, while Joule heating enhances aluminum pile-up in front of the copper asperity due to plowing.