The adsorption of pentacene on Cu(221), Cu(511) and Cu(911) is investigated
using density functional theory (DFT) with the self-consistent inclusion of van
der Waals (vdW) interactions. Cu(211) is a vicinal of Cu(111) while Cu(511) and
(911) are vicinals of Cu(100). For all the three surfaces, we found pentacene
to prefer to adsorb parallel to the surface and near the steps. The addition of
vdW interactions resulted in an enhancement in adsorption energies, with
reference to the PBE functional, of around 2 eV. With vdWs inclusion, the
adsorption energies were found to be 2.98 eV, 3.20 eV and 3.49 eV for Cu(211),
Cu(511) and Cu(911) respectively. These values reflect that pentacene adsorbs
stronger on (100) terraces with a preference for larger terraces. The molecule
tilts upon adsorption with a small tilt angle on the (100) vicinals (about a
few degrees) as compared to a large one on Cu(221) where the tilt angle is
found to be about 20o. We find that the adsorption results in a net charge
transfer to the molecule of ~1 electron, for all surfaces.Comment: 11 pages, 4 figure
