Density functional theory study of the adsorption of alkanethiols on Cu(111), Ag(111), and Au(111) in the low and high coverage regimes
Density functional theory study of the adsorption of alkanethiols on Cu(111), Ag(111), and Au(111) in the low and high coverage regimes
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DOI：
10.1021/jp053273v
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发表时间：
2005-11-24
影响因子：
3.3
通讯作者：
Patrito, EM
中科院分区：
文献类型：
--
作者：
Cometto, FP;Paredes-Olivera, P;Patrito, EM
研究了低覆盖度和高覆盖度下吸附在 Cu(111)、Ag(111) 和 Au(111) 表面上的烷硫醇的结构、表面键合和能量学。在不存在和存在外部施加电场的情况下研究了硫醇/金属相互作用的势能表面（PES），以模拟电极电势对表面键合的影响。电场影响 PES 的波纹，负电场时波纹减小，正电场时波纹增大。在结构研究中，我们考虑了吸附物和表面的弛豫。金原子在垂直于表面的方向上观察到最高弛豫，而银原子在平行于表面的平面上呈现出最高弛豫。表面弛豫在低覆盖率极限下更为重要。通过总态密度和投影态密度分析来研究表面结合。在铜表面观察到最高的离子特征，而最高的共价特征出现在金上。这导致 PES 与吸附物倾斜角对 An(111) 的强烈依赖性，而这种依赖性对其他金属不太明显。因此，吸附物弛豫和金属弛豫对结合能的贡献对于金来说更为重要。为了阐明硫醇对金表面扩散的影响，在111表面以及具有金吸附原子的表面上研究了硫醇在金上的吸附。 CH3CH2S 自由基吸附在金吸附原子上。 CH3CH2SAu 物质的扩散势垒低于裸露金吸附原子的扩散势垒，也低于裸露硫醇自由基的扩散势垒。还研究了分子种类 CH3SH 和 CH3CH2SH 在 Au(111) 上的吸附。它们通过金原子顶部的硫原子吸附。另一方面，完美 111 表面上的烷硫醇自由基的吸附发生在所有金属的低覆盖极限的面心立方 (fcc) 桥位上，并在铜和银的高覆盖极限下向费位移动。
The structure, the surface bonding, and the energetics of alkanethiols adsorbed on Cu(111), Ag(111), and Au(111) surfaces were studied under low and high coverages. The potential energy surfaces (PES) for the thiol/metal interaction were investigated in the absence and presence of externally applied electric fields in order to simulate the effect of the electrode potential on the surface bonding. The electric field affects the corrugation of the PES which decreases for negative fields and increases for positive fields. In the structural investigation, we considered the relaxation of the adsorbate and the surface. The highest relaxation in a direction perpendicular to the surface was observed for gold atoms, whereas silver atoms presented the highest relaxation in a plane parallel to the surface. The surface relaxation is more important in the low coverage limit. The surface bonding was investigated by means of the total and projected density of states analysis. The highest ionic character was observed on the copper surface whereas the highest covalent character occurs on gold. This leads to a strong dependence of the PES with the tilt angle of the adsorbate on An(111) whereas this dependence is less pronounced on the other metals. Thus, the adsorbate-relaxation and the metal-relaxation contributions to the binding energy are more important on gold. The adsorption of thiols on gold was investigated on the 111surface as well as on a surface with gold adatoms in order to elucidate the effect of thiols on the surface diffusion of gold. The CH3CH2S radical adsorbs ontop of the gold adatom. The diffusional barrier of the CH3CH2SAu species is lower than that for a bare gold adatom and is also lower than that for the bare thiol radical. The adsorption of the molecular species CH3SH and CH3CH2SH was also investigated on Au(111). They adsorb via the sulfur atom ontop of a gold atom. On the other hand, the adsorption of the alkanethiol radicals on the perfect 111 surfaces occurs on the face centered cubic (fcc)-bridge site in the low coverage limit for all metals and shifts toward the fee site at high coverage on copper and silver.