A perturbation theory study of H2 on LiF(0 0 1) |
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Authors: | JN Dawoud DB Jack |
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Institution: | a Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street, W. Montreal, Quebec, Canada H4B 1R6 b Department of Physics, 7th October University, Misurata, Libya c Department of Chemistry, University of British Columbia - Okanagan, 3333 University Way, Kelowna, British Columbia, Canada V1V 1V7 |
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Abstract: | In response to recent helium atom scattering (HAS) results, Monte Carlo (MC) simulations and perturbation theory have been performed for H2 on LiF(0 0 1). MC simulations predict that H2 molecules form a series of structures, p(2 × 2), p(8 × 2), p(4 × 2) with coverages Θ = 0.5, 0.625 and 0.75, respectively, that are stable up to 8 K. This is in partial agreement with the HAS results that report c(2 × 2) and c(8 × 2) structures; they agree in terms of coverage and stability, but disagree in terms of symmetry. To reconcile the results of the simulations and experiments, the orientation of the adsorbed H2 molecules was studied using perturbation theory. These calculations show that the adsorbed H2 molecules are azimuthally delocalized and that the structures are c-type rather then p-type. The calculations also indicate that p-H2 and helicoptering o-H2 prefer cationic sites, while cartwheeling o-H2 prefers anionic sites. |
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Keywords: | Hydrogen Deuterium Quantum effects Potential energy surface ortho-Hydrogen-para-hydrogen conversion Monte Carlo simulations LiF |
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