第一性原理研究O2和H2O在ZnO(101-0)表面上的吸附行为

First-principles study of O2 and H 2O adsorbed on ZnO(101-0)surface

运用基于密度泛函理论(DFT)的第一性原理方法研究了O 2和H 2 O单分子在ZnO(101-0)表面上的吸附行为.吸附位点主要考虑了表面的Zn顶位和Zn桥位,同时也考虑了其它可能的吸附行为.对于O 2在ZnO(101-0)表面上的吸附设计了9个模型,H 2 O在ZnO(101-0)表面上的吸附设计了12个模型.通过形成能计算发现,O 2在表面上的吸附为正值,H 2 O的吸附为负值.O 2和H 2 O单分子在表面上发生分子吸附,未见解离形态.对于O 2吸附最稳定的结构是O 2分子与表面相邻的Zn原子形成了Zn slab1-O ads1-O ads2-Zn slab2桥连键.其它较为稳定的结构是O ads1原子迁移到下一个表面重复晶胞的O原子位置附近,在表面上形成了Zn slab1-O ads1键,同时O ads2原子扩散至表面沟渠上方.对于H 2 O吸附,不论以何种方式吸附结构都比较稳定.其中最稳定的构型是O ads迁移到下一个表面重复晶胞的O原子位置附近,形成了Zn slab1-O ads键以及O slab3-H氢键.另外较稳定的构型是O ads迁移到ZnO(101-0)表面台阶上方,形成了Zn slab1-O ads键以及O slab 1-H氢键.

First-principles calculations based on density functional theory(DFT)have been carried out to investigate the adsorption behaviors of O 2 and H 2 O unimolecule on ZnO(101-0)surfaces.The surface adsorbed sites of Zn top and Zn bridge are mainly considered,in addition to this,other possible adsorption behaviors also have been considered.For O 2 adsorbed on ZnO(101-0)surface,nine models have been designed,and twelve for H 2 O adsorption.In all our considered models,the formation energies of O 2 adsorption are positive and negative for H 2 O adsorption.It found that the adsorption is full molecular and no dissociation.For O 2 adsorption,the most favorable structure is O 2 bonding to neighboring Zn atoms and forms Zn slab1-O ads1-O ads2-Zn slab2 bridge bond.The other favorable structure is that O ads1 atom diffuses near to the lattice position where an O atom of the next missing ZnO layer will form Zn slab1-O ads1 bond,and O ads2 atom diffuses to above surface trench.For H 2 O adsorption,no matter how H 2 O adsorbed on surface,the models are more stable.The most stable structure also is that O ads migrates to O atomic lattice position of the next missing ZnO layer to form Zn slab1-O ads1 bond and O slab3-H hydrogen bond.The other favorable structure is that O ads diffuses to above surface terrace to form Zn slab1-O ads bond and O slab 1-H hydrogen bond.