Density functional characterization of adsorption and decomposition of 1-propanethiol on the Ga-rich GaAs (001) surface.
Density functional characterization of adsorption and decomposition of 1-propanethiol on the Ga-rich GaAs (001) surface.
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DOI：
10.1021/jp810435c
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发表时间：
2009-05
期刊：
影响因子：
--
通讯作者：
Shaobin Tang;Z. Cao
中科院分区：
文献类型：
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作者：
Shaobin Tang;Z. Cao
用密度泛函方法研究了1-丙烷乙烷在富Ga GaAs（001）表面的吸附和分解. 1-丙硫醇在GaAs（001）上的解离吸附是相当容易的。其次是C-S键断裂的丙硫醇物种，表面丙基物种形成的低能量路线的势垒为47.2千卡/摩尔。丙基物质是通过C-H键偶联生成丙烷和通过β-H消除生成丙烯的重要前体。在298.1 K下，从丙基物质到丙烷和丙烯的表面过程的预测活化自由能分别为45.2和37.0 kcal/mol，而相对于游离1-丙烷乙烷，反应的相应总吉布斯自由能Δ G分别为-49.3和-21.2 kcal/mol。因此，两种反应途径都是竞争性的，导致产物混合物，尽管从丙基物种中消除β-H最初在动力学上是非常有利的。在此基础上，提出了1-丙烷乙烷在GaAs（001）表面的吸附和热分解机理，计算结果与实验结果符合较好.
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.