First-principles calculation on the zero-bias conductance of a gold/1,4-diaminobenzene/gold molecular junction

摘要

The conductance of a Au/1,4-diaminobenzene/Au molecular junction is investigated using a fully self-consistent ab initio technique which combines the non-equilibrium Green's function formalism with density functional theory. The transmission coefficient at the Fermi level is calculated to be 0.028, in reasonable quantitative agreement with the recent break junction experiments (0.0064). Transport is mainly through the highest occupied molecular orbital (HOMO) and the HOMO-2 state of the 1,4-diaminobenzene molecule. These states are all pi conjugated orbitals formed from the p-orbitals of the two nitrogen atoms and a pi-type orbital on the benzene backbone. Our calculations also demonstrate that these frontier molecular states form two sigma-type bonds with the s-orbitals of the gold adatoms. which is helpful in reducing the dependence of the junction conductance over the anchoring geometry.