title: Adsorption of HF and HCl on the beta-AlF3 (100) surface.
abstract: The current study employs hybrid-exchange density functional theory to investigate the adsorption of HF and HCl to under-coordinated Al ions on the beta-AlF(3) (100) surface. It is shown that the geometries of the adsorbates are strongly dependent on coverage. Furthermore, the adsorption of HCl leads to a number of distinct structures that have very similar energies. It is proposed that this result may explain the high catalytic activity of aluminium fluoride and aluminium chloro-fluoride surfaces towards chlorine-fluorine exchange reactions. The stretching and bending frequencies of the H-F and H-Cl bonds at half and full monolayer coverage are also calculated and the vibrational spectrum is found to be strongly dependent on the adsorption site and the coverage. The vibrational frequency shifts provide, therefore, a mechanism for experimentally characterising these surfaces.
authors.affiliation: Computational Science and Engineering Department, Science and Technology Facilities Council, Daresbury Laboratory, Daresbury, Warrington, Cheshire, UK. c.l.bailey@dl.ac.uk
authors.forename: C L
authors.initials: CL
authors.lastname: Bailey
authors.forename: A
authors.initials: A
authors.lastname: Wander
authors.forename: S
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: B G
authors.initials: BG
authors.lastname: Searle
authors.forename: N M
authors.initials: NM
authors.lastname: Harrison
mesh_terms: D000327:Adsorption; D017607:Aluminum Compounds / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D006851:Hydrochloric Acid / Q000737:chemistry*; D006858:Hydrofluoric Acid / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D013499:Surface Properties
chemical_list: D017607:Aluminum Compounds; D005459:Fluorides; D006851:Hydrochloric Acid; D006858:Hydrofluoric Acid; C032311:aluminum fluoride