Molecular wires (MW) are the fundamentalbuilding blocks for molecular electronic devices. They consist ofa molecular unit connected to two continuum reservoirs ofelectrons (usually metallic leads). We rely on Landauer theory asthe bassi for studying the conductance properties of MW systems.This relates the lead to lead current to the transmissionprobability for an electron to scatter through the molecule. Twodifferent methods have been developed for the study of thisscattering. One is based on a solution of the Lippmann-Schwingerequation and the other solves for the matrix using Schrodinger'sequation. We use our methodology to study two problems ofcurrent interest. The first MW system consists of 1.4-benzene-dithiolate (BDT) bonded to two gold nanocontacts. Ourcalculations show that the conductance is sensitive to thechemical bonding between the molecule and the leads. Thesecond system we study highlights the interesting phenomenon ofantiresonances in MW. We derive an analytic formula predictingat what energies antiresonances should occor in the transmissionspectra of MW. A numerical calculation for a MW consisting offilter molecules attached to an active molecule shows theexistence of an antiresonance at the energy predicted by our formula.
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