Microscopic study of electrical transport through individual molecules with metallic contacts: I. "Band" lineup, voltage drop and high-field transport

We present the first in a series of microscopic studies of electrical transport through individual molecules with metallic contacts. We view the molecules as ``heterostructures'' composed of chemically well-defined atomic groups, and analyze the device characteristics in terms of the charge and potential response of these atomic-groups to the perturbation induced by the metal-molecule coupling and the applied electrical field, which are modeled using a first-principles based self-consistent matrix Green's function (SCMGF) method. As the first example, we examine the devices formed by attaching two benzene-based molecular radicals--phenyl dithiol (PDT) and biphenyl dithiol (BPD)--symmetrically onto two semi-infinite gold electrodes through the end sulfur atoms.