Multiscale modeling of interaction of alane clusters on Al(111) surfaces: A reactive force field and infrared absorption spectroscopy approach

• Published in: The Journal of Chemical Physics
• Main Authors: Ojwang, J. G. O., Chaudhuri, Santanu, van Duin, Adri C. T., Chabal, Yves J., Veyan, Jean-Francois, van Santen, Rutger, Kramer, Gert Jan, Goddard, William A., III
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Institute of Physics 2010
• Subjects: ab initio calculations; aluminium; etching; infrared spectra; molecular clusters; molecular dynamics method; molecular force constants; molecule-surface impact; Iceland
• Online Access: https://doi.org/10.1063/1.3302813

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 × 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. © 2010 American Institute of Physics. Received 20 November 2009; accepted 5 January 2010; published 24 February 2010. This work is part of the research programs of Advanced Chemical Technologies for Sustainability ACTS, which is funded by Nederlandse Organisatie voor Wetenschappelijk Onderzoek NWO. J.G.O.O. thanks Jason Graetz, Geert Jan Kroes, and Andreas Züttel for fruitful discussion on agglomeration process of alanes during the MH2008 conference in Iceland. S.C. acknowledges ONR Grant No. N00014-03-1- 0247. Y.J.C. acknowledges Hydrogen Fuel Initiative Award Grant No. BO-130 of the ...