| Autor: |
Pedersen, Andreas, Karssemeijer, Leendertjan, Cuppen, Herma M., Jónsson, Hannes |
| Zdroj: |
The Journal of Physical Chemistry - Part C; July 2015, Vol. 119 Issue: 29 p16528-16536, 9p |
| Abstrakt: |
Long-time-scale simulations of H2O admolecule diffusion on the (0001) surface of ice Ih were carried out over the temperature range of 100 to 200 K using the adaptive kinetic Monte Carlo method and TIP4P/2005f interaction potential. The arrangement of dangling H atoms was varied from the proton-disordered surface to the perfectly ordered Fletcher surface. A large variety of sites and a broad distribution in adsorption energy for both types of surfaces were found. Up to 4% of the sites on the proton-disordered surface have an adsorption energy exceeding the cohesive energy of ice Ih. The mean squared displacement of a simulated trajectory at 175 K for the proton-disordered surface gave a diffusion constant of 6 × 10–10cm2/s, consistent with an upper bound previously reported from experiments. During the simulation, dangling H atoms rearranged so as to reduce clustering, thereby approaching a linear Fletcher type arrangement. Diffusion on perfectly ordered Fletcher surfaces was estimated to be significantly faster, especially along rows of dangling hydrogen atoms. From simulations over the range in temperature, an effective activation energy of diffusion was estimated to be 0.16 and 0.22 eV for diffusion parallel and perpendicular to the rows, respectively. Even a slightly disordered Fletcher surface has isotropic diffusion. |
| Databáze: |
Supplemental Index |
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