CO在Pt(111)表面吸附的从头算研究

Ab Initio Study for CO Adsorption on Pt(111) Surface

本文在超胞近似和slab模型的基础上,采用广义梯度近似(GGA)下的RPBE(Revised Perdew-Burke-Ernzerhof)泛函对CO-Pt(111)体系进行了理论研究.对体系的吸附能、C-O键和C-Pt键的键长、CO的振动频率以及电子态密度(DOS)进行了计算和分析.结果表明,在0.25ML(mono-layer)的覆盖度下,CO在顶位(top)、桥位(bridge)、两个三重洞位(fcc和hcp)的吸附能非常接近,这说明CO在Pt(111)面比较容易扩散.在顶位,C-O键和C-Pt键的键长分别为1.16和1.85,CO的振动频率为2069cm-1.通过态密度分析表明,CO吸附在桥位和洞位时,其分子轨道3σ、4σ、1π、5σ轨道均参与成键,但是CO吸附在顶位时,仅有4σ、1π、5σ轨道参与成键,这可能与CO吸附在表面时和不同数目的Pt原子结合密切相关.

Based on the super-cell approximation and the slab model,CO adsorption on Pt（111） surface has been investigated by using the RPBE（Revised Perdew-Burke-Ernzerhof） function under the generalized gradient approximation（GGA）.The adsorption energy,bond lengths of C-O and C-Pt,vibrational frequencies and density of states are calculated.The results show that the adsorption energies of CO on the top,bridge,fcc and hcp sites are very close,which indicates that CO on the Pt（111） surface is fairly easy to diffuse at 0.25 mono-layer.On the top site,the C-O and C-Pt bond lengths are 1.16？ and 1.85？,respectively.The vibration frequency of CO is 2069cm-1.According to the density of states analysis,the 3σ-,4σ-,1π-and 5σ-like orbitals are all involved in bonding at the bridge and hollow sites,whereas there are only the 4σ-,1π-and 5σ-like states involved in bonding at the top site.This may be related to the coordination numbers of Pt atoms with C atoms.