Vassilev Peter, van Santen Rutger A, Koper Marc T M
Schuit Institute of Catalysis, Laboratory of Inorganic Chemistry and Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
J Chem Phys. 2005 Feb 1;122(5):54701. doi: 10.1063/1.1834489.
This paper presents a detailed study of a water adlayer adsorbed on Pt(111) and Rh(111) surfaces using periodic density functional theory methods. The interaction between the metal surface and the water molecules is assessed from molecular dynamics simulation data and single point electronic structure calculations of selected configurations. It is argued that the electron bands around the Fermi level of the metal substrate extend over the water adlayer. As a consequence in the presence of the water layer the surface as a whole still maintains its metallic conductivity-a result of a crucial importance for understanding the process of electron transfer through the water/metal interface and electrochemical reactions in particular. Our results also indicate that there exists a weak bond between the hydrogen of the water and the Rh metal atoms as opposed to the widespread (classical) models based on purely repulsive interaction. This suggests that the commonly used classical interactions potentials adopted for large scale molecular dynamics simulations of water/metal interfaces may need revision. Two adsorption models of water on transition metals with the OH bonds pointing towards or away of the surface are also examined. It is shown that due to the very close values of their adsorption energies one should consider the real structure of water on the surface as a mixture of these simple "up" and "down" models. A model for the structure of the adsorbed water layer on Rh(111) is proposed in terms of statistical averages from molecular dynamics simulations.
本文采用周期性密度泛函理论方法，对吸附在Pt(111)和Rh(111)表面的水吸附层进行了详细研究。通过分子动力学模拟数据和选定构型的单点电子结构计算，评估了金属表面与水分子之间的相互作用。研究认为，金属基底费米能级附近的电子能带延伸至水吸附层之上。因此，在有水层存在的情况下，整个表面仍保持其金属导电性——这一结果对于理解电子通过水/金属界面的转移过程，尤其是电化学反应，至关重要。我们的结果还表明，与基于纯排斥相互作用的广泛（经典）模型不同，水的氢与Rh金属原子之间存在弱键。这表明，用于水/金属界面大规模分子动力学模拟的常用经典相互作用势可能需要修正。还研究了水在过渡金属上的两种吸附模型，其中OH键指向表面或远离表面。结果表明，由于它们的吸附能非常接近，应该将表面水的真实结构视为这些简单的“上”和“下”模型的混合。根据分子动力学模拟的统计平均值，提出了Rh(111)表面吸附水层的结构模型。
