Shrinking nanowires by kinetically controlled electrooxidation.

Nanowires composed of antimony, gold, and bismuth telluride (Bi2Te3) were reduced in diameter by electrooxidation in aqueous solutions. When electrooxidation was carried out using low current densities (Jox < 150 microA cm(-2)), the mean wire diameter decreased in direct proportion to the oxidation time, as expected for a kinetically controlled process. Under these conditions, the diameter uniformity of nanowires remained constant as wires were shrunk from initial diameters of more than 120 nm to less than 40 nm, for Sb and Bi2Te3, and less than 60 nm for Au. Oxidized nanowires remained continuous for more than 100 microm. Electrooxidation at higher current densities rapidly introduced breaks into these nanowires. Electrochemical wire growth and shrinking by electrooxidation were integrated into a single electrochemical experiment that allowed the final mean diameter of nanowires to be specified with a precision of 5-10 nm.

Quantum tunneling using entangled classical trajectories.

In this Letter, we present a new method for simulating quantum processes in the context of classical molecular dynamics simulations. The approach is based on solving numerically the quantum Liouville equation in the Wigner representation using ensembles of classical trajectories. Quantum effects arise in this formulation as a breakdown of the statistical independence of the ensemble. New interaction forces between ensemble members are derived, which require the trajectory ensemble representing the state to evolve as an entangled, unified whole. The method is applied to the simulation of quantum tunneling in a one-dimensional model system, yielding excellent agreement with exact quantum calculations.