title: Hydrogen fluoride adsorption and reaction on the α-Al2O3(0001) surface: a density functional theory study.
abstract: The adsorption and reaction behaviors of HF on the α-Al(2)O(3)(0001) surface are systematically investigated using density functional theory method. By increasing the number of HF molecules in a p(2 × 1) α-Al(2)O(3)(0001) slab, we find that HF is chemically dissociated at low coverage; while both physical and dissociative adsorption occurs at a 3/2 monolayer (ML) coverage. At the same coverage (1.0 ML), diverse configurations of the dissociated HF are obtained in the p(2 × 1) model; while only one is observed in the p(1 × 1) slab due to its smaller surface area compared with the former one. Preliminary fluorination reaction study suggests that the total energy of two dissociated HF in the p(2 × 1) slab increases by 1.00 and 0.72 eV for the formation and desorption of water intermediate, respectively. The coadsorption behaviors of HF and H(2)O indicate that the pre-adsorbed water is unfavorable for the fluorination of Al(2)O(3), which is well consistent with the experimental results. The calculated density of states show that the peak of σ(H-F) disappears, while the peaks of σ(H-O) and σ(Al-F) are observed at -8.4 and -5 to -3 eV for the dissociated HF. Charge density difference analysis indicates that the dissociated F atom attracts electrons, while no obvious changes on electrons are observed for the surface Al atoms.
authors.affiliation: Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China.
authors.forename: Jie-Li
authors.initials: JL
authors.lastname: Quan
authors.forename: Bo-Tao
authors.initials: BT
authors.lastname: Teng
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Wen
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhao
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Meng-Fei
authors.initials: MF
authors.lastname: Luo