We show that the inclusion of van der Waals interactions between the isolated molecule (3 amine molecules) and the Au(111) surface leads to good agreement with experimental data on the binding energies. Each molecule adsorbs with a small tilt angle. For the case of 1,4-diaminobenzene (BDA) our calculations reproduce the larger tilt angle measured by photoemission experiments, when intermolecular interactions are included. These results point to not only the importance of vdW interactions to molecule-surface binding, but also that of intermolecular interactions in determining the adsorption geometry and pattern formation.
This work has been reported as a FAST TRACK COMMUNICATION on the Journal of Physics: Condensed Matter [D. Le, M. Aminpour, A. Kiejna and T. S. Rahman, J. Phys.: Condens. Matter 24 222001 (2012)]