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First principles modelling of electron transport through organic molecules

Kurt Stokbro*, Jeremy Taylor, Mads Brandbyge

Mikroelektronik Centret, Technical University of Denmark,
DK-2800 Lyngby, Denmark

This is an abstract for a presentation given at the
Ninth Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is available on the web.


I will review the latest results of the TRANSIESTA package[1] for the modeling of electron transport through organic molecules. The TRANSIESTA package is a new density functional code employing local basis sets[2], combined with a non-equilibrium Greens function transport scheme[3]. With this package we can calculate the selfconsistent electronic structure of a nanostructure when it is subject to an external bias. We have used the method to calculate the electron transport through Benzene-DiThiol(BTD) connected to gold leads. The transport properties have been calculated for a range of different leads, and I will discuss the influence of the coupling between the molecule and the lead on the molecular conductance, and compare with experimental data. We establish the nonequilibrium electrostatic potential through the molecule, when it is subject to an external bias. We find that the voltage does not drop symmetrically through the molecule, even though the structure is symmetric. I will discuss the origin of this effect.




Figure: A. The hexagonal Benzene molecule coupled via sulfur atoms to gold chains. B. The calculated electron density when 1 Volt bias is applied, the colouring shows the voltage drop. C. Contour plot of the voltage drop (0.1 V between contours, electrons move from left to right). Contours of the electron density are shown in dashed.


[1] M. Brandbyge, K. Stokbro, J. Taylor, J. L. Mozos, P. Ordejon, Material Research Society symposium proceedings volume 636, D9.25 (2000).

[2] SIESTA: D. Sanchez-Portal, P. Ordejon, E. Artacho and J. Soler, Int. J. Quantum Chem. 65, 453 (1997).

[3] M. Brandbyge, N. Kobayashi, and M. Tsukada, Phys. Rev. B 60, 17064 (1999). J. Taylor, J. Wang and H. Guo, Phys. Rev. B, vol. 63, 245407

Abstract in RTF format 437,465 bytes

*Corresponding Address:
Kurt Stokbro
Mikroelektronik Centret, Technical University of Denmark
Building 345, DK-2800 Lyngby, Denmark
phone: +45 45255762
fax: +45 45887762


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