Geometrical factors in conductance through molecular films

We have studied the conductance of molecular films as a function of orientation of the molecules in the film with respect to electrodes. Depending on the angle between the axis of the molecules and the normal to the electrode, the conductance may change by more than an order of magnitude. This is a consequence of the strong directional character of p orbitals that determine the conductance through the conjugated molecules. We illustrate this general result on an exactly solvable model and also present the calculations for two different experimentally studied molecular films sandwiched between gold electrodes.