The adsorption of aromatics on sp-metals: Benzene on Al(111)

We have studied the adsorption of benzene on Al(111) using angle-resolved ultraviolet photoelectron, high-resolution electron energy loss, and thermal desorption spectroscopies (ARUPS, HREELS, and TDS, respectively), work function measurements, and by density functional theory (DFT) calculations using the ab-initio VASP code. The analysis of ARUPS and HREELS spectra of a benzene monolayer unambiguously indicate C6v symmetry and a weak benzene-Al interaction in an adsorption geometry with the ring plane parallel to the surface. The weak interaction is confirmed by TDS. The DFT calculations indicate an electrostatic bond and yield an average benzene-Al(111) distance of 3.7 Å. A weak minimum of the potential energy is observed at the hollow adsorption position.