Atomistic simulation of the structural and conductance evolution of Au break junctions

We present a first principles study on the formation of Au nanowires in a break junction under different initial conditions. Density functional theory (DFT) was used to perform structural relaxations on four systems to investigate the effects of varying the number of relaxed layers and the system cross-section on the evolution of the break junction during the elongation process. The effect on the structure evolution by the increment value used for elongation was considered; therefore, structural relaxations with four selected increment values were performed separately. Electron transport calculations using the non-equilibrium Green's function technique combined with DFT (NEGF-DFT) were also performed for each structure obtained from our relaxations. Even though the structures and junction stretching approaches were different, qualitatively similar results were found in all systems, including a single atomic chain and a conductance plateau with value of G ₀ near the breaking point. We also found that the breaking distance and the final structure of the broken junction are different when either the number of relaxed layers or the increment value is changed.