engleski

Conductance of a phenylene-vinylene molecular wire

The conductance of certain classes of pi-conjugated molecules: phenyl ethylene oligomers (Tour wires), phenylene vinylene oligomers (OPV) and polyynes between gold contacts has been investigated. The influence of the contact gap geometry on the transport has been studied for elongated and contracted gaps, as well as various molecular conformations. The calculated current-voltage characteristics show an unusual increase in the low bias conductance with the contact separation. In contrast, for compressed junctions the conductance displays only a very weak dependence on both the separation and related molecular conformation. With the dominant transport contribution arising from the π system of the frontier junction orbitals, all the predicted increases in the conductance arise from the better band alignment between relevant frontier orbitals at the non-equilibrium geometries at the expense of weaker coupling with the contacts. The results also show that pi-conjugated molecules show good molecular wire properties, with the metallic-like conductance in polyynes, which controllably reduces down with the number of phenyl rings in phenyl type oligomers.

Molecular conductance; Nonequilibrium electron transport; Density functional calculations;

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