Using local orbitals in DFT to examine oligothiophene conductance anomalies

At the heart of a quantitatively accurate metal-molecule-metal conductance calculation, the potential profile must reflect the surface physics between the metal and vacuum. In this work, we employ a local orbital basis and calculate the conductance over a suite of Hamiltonians to examine trends within a molecular system using a rapid, selfconsistent scattering matrix method. As discussed above, this is justified as the tunneling barriers within the molecule largely determine the device's qualitative behavior. In this manner, the unexpectedly higher conductance experimentally measured on a four-membered oligothiophene, over its three-membered counterpart, is analyzed by calculating the conductance for a range of multi-atom displacements corresponding to a selected vibrational mode.