Underlayer chemisorption of C on Al(111)

The chemisorption of C atoms on different clusters representing an Al(111) surface was studied by means of the semiempirical MNDO method. Carbon chemi sorption was studied with and without lattice relaxation. The introduction of the C adatom into the clusters was considered and the most favorable che misorption site was evaluated. The hcp in-surface site was identified as th e most stable adsorption site either with or without lattice relaxation. Ch arge density probabilities with and without C chemisorption were also evalu ated and both results are in agreement with recent scanning tunneling micro scopy (STM) experiments. This fact allowed us to use the MNDO method to eva luate the interaction energy of two chemisorbed C atoms in order to underst and the observed formation of an ordered carbon underlayer. The low mobilit y of single isolated C adatoms revealed in STM experiments is also discusse d. (C) 1998 Elsevier Science B.V. All rights reserved.