Theoretical analysis of geometry-correlated conductivity of molecular wire

An approach closer to the in situ modeling of the molecular electronic device is proposed with partial relaxation of the molecular geometry under the interaction of the external electric field. A typical molecular wire (4,4′-(1,4-phenylenedi-2,1-ethynediyl)bis-benzenethiol) has been studied by this methodology using first-principles DFT calculations and non-equilibrium Green's function formalism. It is found that the optimized molecular wire exhibits a different behavior compared with the geometry-frozen one. The HOMO-LUMO gaps, spatial distributions of the frontier molecular orbitals, and the transmission spectra have been used in the explanation of the observations.