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Electronic structure calculations are nowadays an important tool for studying and predicting physical effects of new materials on the nanometerscale. In particular, the electronic transport properties under finite bias are of great interest. To account for systems under bias we extended our screend Korringa-Kohn-Rostoker (SKKR) Green's function method [1,2] to the Keldysh formalism [3] (NEGF). The method was firstly developed for layered systems, i.e. planar junctions [4,5]. However, the electronic structure of nanocontacts under finite bias is usually described via supercells [6]. The drawback of such treatments are either supercell effects because of periodically repeated images of the contact or in the worst case incorrect results. In order to avoid supercell effects we extended our SKKR-NEGF description towards the embedded cluster method \mcite. Both implementations of the Keldysh formalism include the self-consistent treatment of systems under external bias using the nonequilibrium density given in terms of the Keldysh Green function. We present ab initio results of voltage drops, the charge relaxation under finite bias voltage and current-voltage characteristics for the different types of geometries. References [1] R. Zeller, P.H. Dederichs, B. Ujfalussy, L. Szunyogh, and P. Weinberger, Phys. Rev. B 52, 8807 (1995). [2] P. Zahn, I. Mertig, R. Zeller, and P.H. Dederichs, Mat. Res. Soc. Symp. Proc. 475, 525 (1997). [3] L.V. Keldysh, Sov. Phys. JETP 20 (4), 1018 (1965).} [4] J. Henk et al., Journal of Physics: Condensed Matter 18, 2601--2614 (2006). [5] C. Heiliger et al., J. Appl. Phys. 103, 07A709 (2008). [6] M. Brandbyge et al., Phys. Rev. B 65, 165401 (2002). [7] R. Zeller and P. H. Dederichs, Phys. Rev. Lett. 42 (25), 1713 (1979). |
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