Structural changes during the formation of gold single-atom chains: Stability criteria and electronic structure

Under tensile deformation, Au nanowires (NWs) elongate to form single atom chains via a series of intermediate structural transformations. These intermediate structures are investigated using static density-functional theory, with particular attention paid to their behavior under load. The accessibility of these structures and their stability under load are found to be key factors governing the morphological evolution of the NW, while the ground-state energy of the unstrained structures does not correlate well with the observed behavior. Reverse loading conditions are also studied, where a NW is first deformed in tension and then deformed in compression. Again, accessibility and stability under load are the key criteria for predicting the evolution of the NW. Finally, electronic structure studies show abrupt opening and closing of small band gaps during tensile deformation, possibly explaining conductance oscillations observed experimentally. An analysis of the orbital interactions responsible for this unusual band-gap behavior is presented.