  We present a rigorous and computationally efficient method to do a
parameter-free analysis of molecular wires connected to contacts. The
self-consistent field approach is coupled with Non-equilibrium Green's Function
(NEGF) formalism to describe electronic transport under an applied bias.
Standard quantum chemistry software is used to calculate the self-consistent
field using density functional theory (DFT). Such close coupling to standard
quantum chemistry software not only makes the procedure simple to implement but
also makes the relation between the I-V characteristics and the chemistry of
the molecule more obvious. We use our method to interpolate between two extreme
examples of transport through a molecular wire connected to gold (111)
contacts: band conduction in a metallic (gold) nanowire, and resonant
conduction through broadened, quasidiscrete levels of a phenyl dithiol
molecule. We obtain several quantities of interest like I-V characteristic,
electron density and voltage drop along the molecule.
