Universal behaviour in the final stage of the breaking process for metal nanowires

The gentle control of the nanometric distance between two materials has paved the way for the recent experimental studies on the formation and breaking of metal nanocontacts. In this work, the evolution of Al nanowires along the stretching process up to the final breaking is simulated with density functional calculations. This massive computational work involves the breaking of thick wires (with (111) and (100) orientations and 145 and 136 atoms respectively), and the influence of O, C and H impurities on their mechanical and electrical properties. These simulations show that, close to the breaking point, Al nanowires always develop a dimer geometry irrespective of the initial configuration, crystallographic orientation and the presence of point defects, explaining the universal behaviour of the force and the conductance found in the last stages of the stretching process in all the experiments.