Maksymovych Peter, Sorescu Dan C, Dougherty Dan, Yates John T
Surface Science Center, Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
J Phys Chem B. 2005 Dec 1;109(47):22463-8. doi: 10.1021/jp058154u.
The chemisorption of the undissociated CH3SH molecule on the Au(111) surface has been studied at 5 K using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The molecule was found to adsorb on atop Au sites on the defect-free surface. CH3SH undergoes hindered rotation about the Au-S bond on the defect-free surface which is seen in STM as a time-averaged 6-fold pattern. The pattern suggests that the potential minima directions occur for the rotating molecule at the six hollow sites surrounding the atop adsorption site. The barrier for rotation, obtained by DFT calculations, is approximately 0.1 kcal.mol(-1). At low coverages, preferential adsorption occurs at defect sites in the surface, namely, the herringbone "elbows" and random atomic step sites. Molecules adsorbed on these sites do not exhibit rotational freedom.
利用扫描隧道显微镜（STM）和密度泛函理论（DFT）计算，在5 K下研究了未解离的CH3SH分子在Au(111)表面的化学吸附。发现该分子吸附在无缺陷表面的顶位Au原子上。CH3SH在无缺陷表面围绕Au-S键进行受阻旋转，这在STM中表现为时间平均的六重图案。该图案表明，旋转分子在顶位吸附位点周围的六个空穴位点处出现势能极小值方向。通过DFT计算得到的旋转势垒约为0.1 kcal·mol⁻¹。在低覆盖度下，优先吸附发生在表面的缺陷位点，即人字形“肘部 ”和随机原子台阶位点。吸附在这些位点上的分子不表现出旋转自由度。
