2026-04-17T05:27:43Zhttps://recercat.cat/oai/request

oai:recercat.cat:2445/1643242025-11-19T20:34:30Zcom_2072_1057col_2072_478796col_2072_478917

urn:hdl:2445/164324 Adsorption of atomic oxygen and nitrogen at β-cristobalite (100): a density functionaly theory study Arasa Cid, Carina Gamallo Belmonte, Pablo Sayós Ortega, Ramón Adsorció Teoria del funcional de densitat Quimiosorció Adsorption Density functionals Chemisorption The adsorption of atomic oxygen and nitrogen on the -cristobalite (100) surface is investigated from first principles density functional calculations within the generalized gradient approximation. A periodic SiO2 slab model (6 layers relaxing 4 or 6) ended with a layer of Si or O atoms is employed throughout the study. Several adsorption minima and diffusion transition states have been characterized for the two lowest spin states of both systems. A strong chemisorption is found for either O or N in several sites with both slab endings (e.g., it is found an average adsorption energy of 5.89 eV for O (singlet state) and 4.12 eV for N (doublet state) over the Si face). The approach of O or N on top O gives place to the O2 and NO abstraction reactions without energy barriers. Atomic sticking coefficients and desorption rate constants have been estimated (300 - 1900 K) by using the standard transition state theory. The high adsorption energies found for O and N over silica point out that the atomic recombination processes (i.e., Eley-Rideal and Langmuir-Hinshelwood mechanisms) will play a more important role in the atomic detachment processes than the thermal desorption processes. Furthermore, the different behavior observed for the O and N thermal desorption processes suggests that the published kinetic models for atomic O and N recombination reactions on SiO2 surfaces, based on low adsorption energies (e.g., 3.5 eV for both O and N ), should probably be revised. 2020-06-04T14:00:25Z 2020-06-04T14:00:25Z 2005 2020-06-04T14:00:25Z info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion Versió postprint del document publicat a: https://doi.org/10.1021/JP044064Y Journal of Physical Chemistry B, 2005, vol. 109, num. 31, p. 14954-14964 https://doi.org/10.1021/JP044064Y (c) American Chemical Society , 2005 info:eu-repo/semantics/openAccess American Chemical Society Articles publicats en revistes (Ciència dels Materials i Química Física)