Ni(111)表面二氧化硫分子单层膜的原子结构

Atomic structure of sulfur dioxide monolayers on Ni(111)

目的:研究0.25 ML覆盖度时Ni(111)表面二氧化硫(SO 2)的分子链、单层膜、SO 2/Ni(111)吸附系统的原子结构。方法:基于密度泛函理论的第一性原理,CASTEP模块。结果:分子链或分子膜的能量比单分子能量更低时该系统稳定,吸附系统的能量比衬底和分子膜的能量之和更低时吸附系统稳定。稳定的SO 2分子链有一系列,其中分子与分子链的夹角α为50°~90°;稳定的SO 2单层膜只有一个,其中夹角α为90°;SO 2/Ni(111)有两个稳定的吸附结构,其一SO 2的S原子和两个O原子都吸附在顶位,其二SO 2的S原子吸附在表面的顶位而两个O原子吸附在桥位。结论:这是一个分子自组装系统,许多SO 2单分子自组装成若干稳定的分子链,然后许多SO 2分子链自组装成一个稳定的单层膜,最后SO 2单层膜平铺吸附在Ni(111)表面。比较吸附前后SO 2单层膜的结构参数,可知Ni衬底对对分子单层膜结构影响很小。

Aims: This paper studies the atomic structure of SO2 molecular chains, monolayers and SO2/Ni(111) adsorption systems at 0.25 ML coverage. Methods: The first-principle theory based on density functional theory, CASTEP code. Results: The system was stable when the energy of the molecular chain or monolayer was lower than that of single molecules. And the adsorption system was stable when the energy of the adsorption system was lower than that of the substrate and monolayer. There were a series of stable SO2 molecular chains, in which the angle α between molecule and molecule chain was 50°~90°;There was only one stable SO2 monolayer with the angle α at 90°;There were two stable adsorption structures of the SO2/Ni(111) system, one of which was the S. And two O atoms of SO2 were all adsorbed on the top sites, and the other of the S atom was adsorbed on the top site, while two O atoms were both adsorbed on the bridges. Conclusions: This is a molecular self-assembly system. SO2 single molecules self-assemble into stable molecular chains. Then SO2 molecular chains self-assemble into a stable monolayer. Finally, the SO2 monolayers is adsorbed on the surface of Ni(111). Compared with the structure parameters of SO2 monolayers before and after adsorption, it can be seen that Ni substrate has little influence on the structure of monolayers.