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Polyyne oligomers as almost perfect molecular wires

We report the results of the calculations of electronic structure and transport properties of distinct classes of dithiolated polyyne oligomers chemisorbed onto the gold electrodes. The transmission spectra and the current-voltage characteristics of the considered nanostructures were obtained in a low bias regime with a full self-consistent ab initio description of the molecule and the electrodes with different electrochemical potentials. The calculations were carried out using a nonequilibrium Green`s functions technique based on the density functional theory. The calculated current-voltage characteristics of the systems have shown a weak nonexponential decrease of the conductivity with the increased length of the molecules. We found the conductance of polyyne based wires more than an order of magnitude higher when compared with polyenes and phenylene conjugated oligomers. In contrast to the cumulenes the conductance was not prone to oscillations with the length of the molecule. It appeared to be a very weakly dependent on the molecular length and nearly constant in the wide range of bias voltages

polyynes; nanostructure; conductance

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