Combining density functional theory

Combining density functional theory calculations for molecular electronic structure with a Greenfunction method for electron transport, we calculate from first principles the molecular conductance ofbenzene connected to two Au leads through different anchoring atomssS, Se, and Te. The relaxed atomicstructure of the contact, different lead orientations, and different adsorption sites are fully considered. Wefind that the molecule-lead coupling, electron transfer, and conductance all depend strongly on theadsorption site, lead orientation, and local contact atomic configuration. For flat contacts the conductancedecreases as the atomic number of the anchoring atom increases, regardless of the adsorption site, leadorientation, or bias. For small bias this chemical trend is, however, dependent on the contact atomicconfiguration: an additional Au atom at the contact with the (111) lead changes the best anchoring atomfrom S to Se, although for large bias the original chemical trend is recovered.