Nanowires: Size evolution, reversibility, and one-atom contacts

Size-evolutionary patterns of mechanical and electronic transport properties in junctions are discussed, showing formation of nanowires upon narrowing, regardless of the initial dimensions of the junctions. Mechanical and conductance reversibility of such nanowires in elongation and compression cycles is studied. Ab-initio local-spin-density functional based molecular dynamics simulations show formation of a stable ''one-atom'' contact in a sodium wire at 189K, with the atomic structure near the apex of the nanowire correlated to that of two pentagonal pyramidal Na-7 clusters joined by the apex atom. The average electronic conductance through the one-atom contact, at 189 K, is estimated to be similar to 4.5 (2e(2)/h).