Characterization of Lewis acid sites on the (100) surface of beta-AlF3: Ab initio calculations of NH3 adsorption.
The current study employs hybrid-exchange density functional theory to show that the Lewis base, NH(3), binds to the beta-AlF(3) (100) surface with a binding energy (BE) of up to -1.96 eV per molecule. This is characteristic of a strong Lewis acid. The binding of NH(3) to the surface is predominately due to electrostatic interactions. There is only a small charge transfer from the NH(3) molecule to the surface. The BE as a function of coverage is computed and used to develop a lattice Monte Carlo model which is used to predict the temperature programed desorption (TPD) spectrum. Comparison with experimental TPD studies of NH(3) from beta-AlF(3) strongly suggests that these structural models and binding mechanisms are good approximations to those that occur on real AlF(3) surfaces.
Computational Science and Engineering Department, STFC Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD, United Kingdom. c.l.bailey@dl.ac.uk
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Bailey
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Wander
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Mukhopadhyay
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Searle
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Harrison