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

We have studied the adsorption of benzene on Al(111) using angle-resolved u ltraviolet photoelectron. high-resolution electron energy loss, and thermal desorption spectroscopies (ARUPS, HREELS, and TDS, respectively), work fun ction measurements, and by density functional theory (DFT) calculations usi ng the ab-initio VASP code. The analysis of ARUPS and HREELS spectra of a b enzene monolayer unambiguously indicate C-6v 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 ind icate an electrostatic bond and yield an average benzene-Al(111) distance o f 3.7 Angstrom. A weak minimum of the potential energy is observed at the h ollow adsorption position. (C) 2000 Elsevier Science B.V. All rights reserv ed.