Showing papers by "Fernando Flores published in 2014"

The role of charge transfer in the energy level alignment at the pentacene/C60 interface

Abstract: Understanding the mechanism of energy level alignment at organic–organic interfaces is a crucial line of research to optimize applications in organic electronics. We address this problem for the C60–pentacene interface by performing local-orbital Density Functional Theory (DFT) calculations, including the effect of the charging energies on the energy gap of both organic materials. The results are analyzed within the induced density of interface states (IDIS) model. We find that the induced interface potential is in the range of 0.06–0.10 eV, in good agreement with the experimental evidence, and that such potential is mainly induced by the small, but non-negligible, charge transfer between the two compounds and the multipolar contribution associated with pentacene. We also suggest that an appropriate external intercompound potential could create an insulator–metal transition at the interface.

Statistical analysis of stretched aluminum nanowires

Abstract: We present a statistical analysis of the mechanical and transport properties of stretched Al nanowires. A molecular dynamics density functional theory is used in combination with annealing techniques to analyze a large amount of stretching processes and new realistic geometries. From these calculations, we generate a conductance histogram that is compared with the experimental evidence. New particular geometries appear frequently, and a correlation between these new structures and the peaks in the conductance histogram can be fairly established. In particular, at the first stages of the nanowire elongation, we find a configuration with Al–Al bonds oriented along the stretching direction that is related to the peak appearing at 3 G 0 in the conductance histogram. Besides, an Al–Al dimer is found in most of the cases at the nanowire neck in the last stage of the nanowire stretching, just before the breaking point; this configuration is reflected in the peak found in the conductance histogram at 1 G 0.

Electron transport signature of H2 dissociation on atomic gold wires

Abstract: Nonequilibrium Green's functions calculations based on density functional theory show a direct link between the initial stages of ${\mathrm{H}}_{2}$ dissociation on a gold atomic wire and the electronic current supported by the gold wire. The simulations reveal that for biases below the stability threshold of the wire, the minimum-energy path for ${\mathrm{H}}_{2}$ dissociation is not affected. However, the electronic current presents a dramatic drop when the molecule initiates its dissociation. This current drop is traced back to quantum interference between electron paths when the molecule starts interacting with the gold wire.