title: Multiscale modeling of interaction of alane clusters on Al(111) surfaces: a reactive force field and infrared absorption spectroscopy approach.
abstract: We have used reactive force field (ReaxFF) to investigate the mechanism of interaction of alanes on Al(111) surface. Our simulations show that, on the Al(111) surface, alanes oligomerize into larger alanes. In addition, from our simulations, adsorption of atomic hydrogen on Al(111) surface leads to the formation of alanes via H-induced etching of aluminum atoms from the surface. The alanes then agglomerate at the step edges forming stringlike conformations. The identification of these stringlike intermediates as a precursor to the bulk hydride phase allows us to explain the loss of resolution in surface IR experiments with increasing hydrogen coverage on single crystal Al(111) surface. This is in excellent agreement with the experimental works of Go et al. [E. Go, K. Thuermer, and J. E. Reutt-Robey, Surf. Sci. 437, 377 (1999)]. The mobility of alanes molecules has been studied using molecular dynamics and it is found that the migration energy barrier of Al(2)H(6) is 2.99 kcal/mol while the prefactor is D(0)=2.82 x 10(-3) cm(2)/s. We further investigated the interaction between an alane and an aluminum vacancy using classical molecular dynamics simulations. We found that a vacancy acts as a trap for alane, and eventually fractionates/annihilates it. These results show that ReaxFF can be used, in conjunction with ab initio methods, to study complex reactions on surfaces at both ambient and elevated temperature conditions.
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015, USA. jojwang@ciw.edu
authors.forename: J G O
authors.initials: JG
authors.lastname: Ojwang
authors.forename: Santanu
authors.initials: S
authors.lastname: Chaudhuri
authors.forename: Adri C T
authors.initials: AC
authors.lastname: van Duin
authors.forename: Yves J
authors.initials: YJ
authors.lastname: Chabal
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Veyan
authors.forename: Rutger
authors.initials: R
authors.lastname: van Santen
authors.forename: Gert Jan
authors.initials: GJ
authors.lastname: Kramer
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard