Pecher Josua, Tonner Ralf
Faculty of Chemistry and Material Sciences Centre, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032, Marburg, Germany.
Chemphyschem. 2017 Jan 4;18(1):34-38. doi: 10.1002/cphc.201601129. Epub 2016 Nov 18.
Intermediate states to covalent attachment of molecules on surfaces, so called precursors, are usually considered to be physisorbed and mobile. We show that this view should be reconsidered and provide evidence for a chemisorbed precursor for ethylene on Si(001). The character of the molecule-surface bond as a π complex is determined and quantified using our recently developed method for energy and charge analysis in extended systems. In contrast to previous assumptions, the precursor should thus be immobile, which is underlined by computation of high diffusion energy barriers. This has important implications for understanding and modelling of adsorption kinetics. Our analysis highlights that taking the viewpoint of molecular chemistry helps uncover important aspects in the adsorption process on surfaces. Previous experimental results that appear to be in contrast to our model are examined and reinterpreted.
分子在表面共价附着的中间态，即所谓的前驱体，通常被认为是物理吸附且可移动的。我们表明这种观点应被重新审视，并为乙烯在Si(001)上的化学吸附前驱体提供证据。使用我们最近开发的扩展系统能量和电荷分析方法，确定并量化了作为π络合物的分子-表面键的性质。与先前的假设相反，因此前驱体应该是不可移动的，这一点通过高扩散能垒的计算得到了强调。这对于理解和模拟吸附动力学具有重要意义。我们的分析强调，从分子化学的角度有助于揭示表面吸附过程中的重要方面。对先前似乎与我们模型相矛盾的实验结果进行了检查和重新解释。
