Max Koentopp

Density functional calculations of nanoscale conductance

Density functional calculations for the electronic conductance of single molecules are now common. We examine the methodology from a rigorous point of view, discussing where it can be expected to work, and where it should fail. When molecules are weakly coupled to leads, local and gradient-corrected approximations fail, as the Kohn–Sham levels are misaligned. In the weak bias regime, exchange–correlation corrections to the current are missed by the standard methodology. For finite bias, a new methodology for performing calculations can be rigorously derived using an extension of time-dependent current density functional theory from the Schrodinger equation to a master equation.

Zero-bias molecular electronics : Exchange-correlation corrections to Landauer's formula

Institute of Nanotechnology, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany(Dated: February 2, 2008)We show, that standard first principles calculations of transport through single molecules missexchange-correlation corrections to the Landauer formula—the conductance is calculated at theHartree level. Furthermore, the lack of derivative discontinuity in approximations can cause largeerrors for molecules weakly coupled to the electrodes. From Kubo response theory, both the Lan-dauer formula and these corrections in the limit of zero bias are derived and calculations presented.

Coherent transport through a molecular wire: DFT calculation

Abstract We report calculations using density functional theory (DFT) for the conductance of an organic molecule that has been studied experimentally by Reichert et al. (Phys. Rev. Lett. 88 (2002) 176804). Our calculations are based on the nonequilibrium Greens function formalism and on density functional calculations using TURBOMOLE. We find qualitative agreement with experimental findings. In order to address possible reasons for quantitative discrepancies a detailed study of the conductance change upon modification of the microscopic conditions (e.g. the sulfur–gold bonding) is presented.