Molecular Dynamics Simulations of the Influence of Surface Temperature on the Trapping of Methane on Iridium Single-Crystalline Surfaces

• Published in: The journal of physical chemistry. B Vol. 106; no. 33; pp. 8349 - 8353
• Main Authors: Sitz, G. O, Mullins, C. B
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22.08.2002
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp020867e

Classical molecular dynamics simulations have been performed to model the temperature dependence on trapping of methane on the (111) and the reconstructed (110) surfaces of iridium. Methane is modeled as a monatomic particle of mass 16 amu. The simulations suggest that on the (110)−(1 × 2) surface that the trapping probability scales nearly with total energy and that close to normal energy scaling is prevalent on the (111) surface, consistent with what is known from experimental measurements. Further, the simulations are in reasonable quantitative agreement with the measured trapping probabilities at a surface temperature of 65 K. For the highest surface temperature that we employed in the simulations, T s = 1465 K, methane molecules that trapped appeared to be thermalized with the surface as determined by the translational energies and the angular distribution of the desorbing molecules. Additionally, the trapped molecules had calculated surface lifetimes that corresponded well with the physical adsorption well depth and surface temperature. The effect of surface temperature on the value of the trapping probability is complicated and strongly dependent upon the initial translational energy of the impinging particle; the trapping can both increase and decrease with increasing surface temperature. However, the values for trapping that we calculate from our simulations do not deviate markedly from their low-temperature values.