双原子卤素分子在石墨烯上吸附的van der Waals密度泛函研究
Adsorption of diatomic halogen molecules on graphene: A van der Waals density functional study
摘要：
采用密度泛函理论，考虑非局域关联效应，采用vdW-DF方法研究了氟、氯、溴和碘双原子分子在石墨烯上的吸附.结果表明，范德华相互作用在石墨烯和卤素分子之间形成化学键中起着至关重要的作用，因此对于正确描述该系统中的吸附是重要的。已经发现分子的面内取向比垂直于石墨烯层的取向更稳定。在F $_2$、Br $_2$和I $_2$的情况下，我们还发现离子对结合能的贡献，随着距离的增加而慢慢消失。电子结构的分析表明，离子相互作用是由于电荷从石墨烯转移到分子。此外，我们发现，杂质浓度的增加导致导带形成的石墨烯由于卤素分子之间的相互作用。此外，还研究了卤素分子对石墨的插层作用。在卤素分子的存在下，石墨层之间的结合变得显着减弱，这是根据最近的实验结果的声化学剥离的插层石墨。
英文摘要：
The adsorption of fluorine, chlorine, bromine, and iodine diatomic molecules on graphene has been investigated using density functional theory with taking into account nonlocal correlation effects by means of vdW-DF approach. It is shown that the van der Waals interaction plays a crucial role in the formation of chemical bonding between graphene and halogen molecules, and is therefore important for a proper description of adsorption in this system. In-plane orientation of the molecules has been found to be more stable than the orientation perpendicular to the graphene layer. In the cases of F$_2$, Br$_2$ and I$_2$ we also found an ionic contribution to the binding energy, slowly vanishing with distance. Analysis of the electronic structure shows that ionic interaction arises due to the charge transfer from graphene to the molecules. Furthermore, we found that the increase of impurity concentration leads to the conduction band formation in graphene due to interaction between halogen molecules. In addition, graphite intercalation by halogen molecules has been investigated. In the presence of halogen molecules the binding between graphite layers becomes significantly weaker, which is in accordance with the results of recent experiments on sonochemical exfoliation of intercalated graphite.
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