School of Materials Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, 127 YouYi Western Road, Xi'an, Shaanxi 710072, China.
J Chem Phys. 2013 Apr 7;138(13):134708. doi: 10.1063/1.4799557.
Density functional theory calculations were used to examine the effects of intrinsic surface defects of Cu(111) on the adsorption of methylthiol (CH3SH). The examination covers both the initial non-dissociative adsorption and the subsequent dissociation reaction pathways to form intermediate and final reaction products. By comparing the most probable adsorption structures likely formed after the adsorption of CH3SH on Cu(111) with and without the presence of adatoms (Cu(ad)) and vacancies, this computational work offers new insights about the geometry and thermodynamic stability of these structures. Particularly, it reveals a new type of surface complexes having two CH3S bonding to one Cu(ad) (referred therein as CH3S-Cu(ad)-CH3S). In addition, this work also yields new reaction dynamics results on transition states and activation barriers. The results reveal that the presence of Cu(ad) indeed significantly changes the kinetics of adsorption and dissociation of CH3SH on Cu(111). The most kinetically favorable reaction pathway turns out to be that involving the formation of a special surface complex formed by one Cu(ad) plus two CH3S fragments from the dissociation of CH3SH, with the two S atoms located at the bridge sites of Cu(111). Finally, this work also gives simulated scanning tunneling microscopic images for the most important adsorption species in the course of the transition from CH3SH∕Cu(111) to CH3S∕Cu(111), which may stimulate future experimental studies of self-assembled monolayers on practical metal substrates such as thiols on copper.
采用密度泛函理论计算研究了 Cu(111) 表面本征缺陷对甲基硫醇（CH3SH）吸附的影响。研究涵盖了 CH3SH 在 Cu(111)上的初始非解离吸附以及随后的解离反应途径，以形成中间和最终反应产物。通过比较 CH3SH 在 Cu(111)上吸附后可能形成的最可能吸附结构，有无 adatoms（Cu(ad)）和空位，这项计算工作提供了关于这些结构的几何形状和热力学稳定性的新见解。特别是，它揭示了一种新型的表面络合物，其中两个 CH3S 键合到一个 Cu(ad)（在文中称为 CH3S-Cu(ad)-CH3S）。此外，这项工作还提供了关于过渡态和活化能垒的新反应动力学结果。结果表明，Cu(ad) 的存在确实显著改变了 CH3SH 在 Cu(111)上的吸附和解离动力学。最动力学有利的反应途径是涉及由 CH3SH 解离形成的一个特殊表面络合物的形成，其中一个 Cu(ad)和两个 CH3S 片段，两个 S 原子位于 Cu(111)的桥位上。最后，这项工作还给出了在 CH3SH∕Cu(111)到 CH3S∕Cu(111)的转变过程中最重要的吸附物种的模拟扫描隧道显微镜图像，这可能会激发未来在实际金属基底上自组装单层（如铜上的硫醇）的实验研究。
