Generalized tight-binding approach for molecular electronics modeling

We discuss a generalized tight-binding approach for transport calculations in molecular electronics. The parameters of the tight-binding model are directly calculated from ab initio quantum chemistry calculations for a molecular tunneling device. A Green's function approach based on the Caroli formula is used to calculate the transport properties. Our approach is unique in that it readily separates contributions to the total tunneling current from individual Bloch eigenstates (transverse electronic modes or channels) of the electrodes, thus providing a powerful tool in understanding how tunneling is affected by the electronic structure of the electrodes and molecule. The tight-binding model also allows us to show that the placement of the Fermi energy in the electrodes can change the tunneling conductance by orders of magnitude. (C) 2003 Wiley Periodicals, Inc.