The conductance of a single 4,4 bipyridine (44BPD) molecule connected to two gold electrodes is calculated using a density functional theory based Green function method. The atomic geometry of such a molecular junction is constructed from the optimized structure of a gold trimer-44BPD-gold trimer complex. Resonant conduction is the main feature of its transport properties. The magnitude of the transmission coefficient at the Fermi level is determined to be T = 1.01 × 10(-2), which is in excellent agreement with the experimental value. The dependence of the transmission on the Au-N bond length and the torsion angle is also discussed.
Three types of 11-electron analytic effective core potentials (ECPs) and their corresponding double-zeta and single-zeta basis sets of gold are evaluated using density functional theory (DFT) calculations. We find that, compared with basis sets derived for use with Hatree-Fock-based Los Alamos (LANL1) and Ermler-Christiansen (EC) ECPs, the DFT-derived Troullier-Martins (TM) ECP together with a single-zeta basis set (TMSZ) is more suitable to describe not only the interaction between gold atoms with a benzene-1,4-dithiolate molecule but also the electronic structure of an infinite 1-dimensional monatomic gold chain. Hence, TMSZ is the best single-zeta basis set with an 11-electron ECP for gold available currently to be used in theoretical calculations on electrical properties of molecular electronic devices with DFT based Green's function method employing a finite analytic basis of local orbitals.
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