Density functional characterization of adsorption and decomposition of 1-propanethiol on the Ga-rich GaAs (001) surface.
Density functional calculations have been used to investigate adsorption and decomposition of 1-propanethiol on the Ga-rich GaAs (001) surface. The dissociative adsorption of 1-propanethiol on GaAs (001) to the chemisorbed propanethiolate and hydrogen was predicted to be quite facile. Followed by the C-S bond scission of the propanethiolate species, the surface propyl species was formed with a barrier of 47.2 kcal/mol for the low-energy route. The propyl species is an important precursor to propane through the C-H bond coupling and to propene via the beta-H elimination. Predicted activation free energies for the surface processes from the propyl species to propane and propene are 45.2 and 37.0 kcal/mol at 298.1 K, respectively, while the corresponding overall Gibbs free energies of reaction DeltaG are -49.3 and -21.2 kcal/mol relative to free 1-propanethiol. Therefore, both reaction routes are competitive, resulting in a product mixture, although the beta-H elimination from the propyl species is initially remarkably favorable dynamically. On the basis of our calculations, detailed mechanisms for adsorption and thermal decomposition of 1-propanethiol on the GaAs (001) surface were proposed, and the calculated results show good agreement with experimental observations.
Department of Chemistry and State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 360015, China.
Shaobin
S
Tang
Zexing
Z
Cao