Structure and Bonding of Alkanethiols on Cu(111) and Cu(100)
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- 作者：A. Ferral ; E. M. Patrito ; P. Paredes-Olivera
- 刊名：Journal of Physical Chemistry B
- 出版年：2006
- 出版时间：August 31, 2006
- 年：2006
- 卷：110
- 期：34
- 页码：17050 - 17062
- 全文大小：1973K
- 年卷期：v.110,no.34(August 31, 2006)
- ISSN：1520-5207
文摘
The local structure of the sulfur atom of methanethiolate and ethanethiolate on the Cu(111) and Cu(100)surfaces was investigated from first principles employing the periodic supercell approach in the frameworkof density functional theory. On the 111 surface, we investigated the (
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and (2 × 2) structures,whereas on the 100 surface, we investigated the p(2 × 2) and c(2 × 2) structures. The landscape of thepotential energy surface on each metal surface presents distinctive features that explain the local adsorptionstructure of thiolates found experimentally. On the Cu(111) surface, the energy difference between the hollowand bridge sites is only 3 kcal/mol, and consequently, adsorption sites ranging from the hollow to the bridgesite were observed for increasing surface coverages. On the Cu(100) surface, there is a large energy differenceof 12 kcal/mol between the hollow and bridge sites, and therefore, only the 4-fold coordination was observed.The high stabilization of thiolates on the hollow site of Cu(100) may be the driving force for the pseudosquarereconstruction observed experimentally on Cu(111). Density of states analysis and density difference plotswere employed to characterize the bonding on different surface sites. Upon interaction with the metal dbands, the 
* orbital of methanethiolate splits into several peaks. The two most prominent peaks are locatedon either edge of the metal d band. They correspond to bonding and antibonding S-Cu interactions. In thecase of ethanethiolate, all the back-bonds are affected by the surface bonding, leading to alternating regionsof depletion and accumulation of charge in the successive bonds.
and (2 × 2) structures,whereas on the 100 surface, we investigated the p(2 × 2) and c(2 × 2) structures. The landscape of thepotential energy surface on each metal surface presents distinctive features that explain the local adsorptionstructure of thiolates found experimentally. On the Cu(111) surface, the energy difference between the hollowand bridge sites is only 3 kcal/mol, and consequently, adsorption sites ranging from the hollow to the bridgesite were observed for increasing surface coverages. On the Cu(100) surface, there is a large energy differenceof 12 kcal/mol between the hollow and bridge sites, and therefore, only the 4-fold coordination was observed.The high stabilization of thiolates on the hollow site of Cu(100) may be the driving force for the pseudosquarereconstruction observed experimentally on Cu(111). Density of states analysis and density difference plotswere employed to characterize the bonding on different surface sites. Upon interaction with the metal dbands, the * orbital of methanethiolate splits into several peaks. The two most prominent peaks are locatedon either edge of the metal d band. They correspond to bonding and antibonding S-Cu interactions. In thecase of ethanethiolate, all the back-bonds are affected by the surface bonding, leading to alternating regionsof depletion and accumulation of charge in the successive bonds.