The mechanical elongation of a finite gold nanowire has been studied by molecular dynamics simulations using different semiempirical potentials for transition metals. These potentials have been widely used to study the mechanical properties of finite metal clusters. Combining with density functional theory calculations along several atomic-configuration trajectories predicted by different semiempirical potentials, the authors conclude that the second-moment approximation of the tight-binding scheme (TB-SMA) potential is the most suitable one to describe the energetics of finite Au clusters. They find that for the selected geometries of Au wires studied in this work, the ductile elongation of Au nanowires along the [001] direction predicted by the TB-SMA potential is largely independent of temperature in the range of 0.01-298 K. The elongation leads to the formation of monatomic chains, as has been observed experimentally. The calculated force-versus-elongation curve is remarkably consistent with available experimental results.

The mechanism of the formation of different junction structures of gold nanowires under stretching has been studied by comprehensive molecular dynamics (MD) simulations using the second-moment approximation of the tight-binding (TB-SMA) potential. The simulations (540 MD runs in total) reveal that there is an inherent rate-dependent energy release law that unifies the effects of the system size, the temperature, and elongation rate on the dynamic elongations of gold nanowires.

The bonding geometry at the metal-molecule interface plays an important role in determining the conductance behavior of metal-molecule-metal junctions. This bonding geometry has to be determined a priori in quantum mechanical current-voltage (I-V) calculations. To identify the detailed metal-molecule bonding configurations, we perform classical molecular simulations by combining grand canonical Monte Carlo (GCMC) sampling with molecular dynamics (MD) to explore the dynamic elongations of gold nanowires in the presence of benzenedithiol (BDT) molecules. A specific multitime-scale double reversible reference system propagator algorithm (double-RESPA) has been designed for the metal-organic complex in MD simulations to improve the simulation efficiency. We investigate the variations of bonding sites and bonding angles of BDT molecules on a stretched Au nanowire at a constant chemical potential. The density of BDT and the number of bonded and nonbonded BDT molecules in the simulation box is monitored during the entire elongation process. Simulation results show that BDT molecules can form a denser monolayer on Au nanowires than at the Au (111) surface, owing to the many atomic steps on curved surfaces. Moreover, the chemical bonding of BDT on the Au nanowire significantly effect the elongation behavior of Au nanowires compared with those in vacuum. Our present results will be valuable to the understanding of the broken junction mechanism in molecular electronics conductance measurements.