摘要
在密度泛函理论的框架下,采用嵌入点电荷簇模型研究了O_2在具有氧缺陷和镁缺陷MgO(001)表面上的吸附.用电荷自洽的方法确定了点电荷的值.计算结果表明,O_2倾向吸附在具有氧缺陷的MgO(001)表面上.通过和我们近期研究过的O_2在低配位的边、角上吸附结果相比较,发现具有氧缺陷的MgO(001)表面更加有利于O_2的吸附和解离.Mulliken电荷分析表明,电荷由底物向吸附的O_2反键轨道上转移是导致O_2键强削弱的主要原因.势能曲线表明,O_2在具有氧缺陷的MgO(001)表面上发生解离所需要克服的能垒比在角阳离子端发生解离所需克服的能垒有大幅度降低.
The adsorption Of O-2 at oxygen vacancy site (F, F+ or F2+ site) and magnesium vacancy site (V, V- or V2- site) has been studied using cluster models embedding in a large array of point charges coupled to density functional method at B3LYP/6-31G ( d) level. The value of point charges is determined by the self-consistent technique. The calculated results indicate that the MgO (00 1) surface with oxygen vacancies has more excellent catalyst structure contributing to the adsorptive-decomposition Of O-2 in comparison with the low-coordinated corner site in the previous study. The adsorption energies for O-2 adsorbed on MgO(001) surface with oxygen vacancies are larger than those on MgO(001) surface with magnesium vacancies. Moreover, the MgO(001) surface with magnesium vacancies hardly exhibits catalytic reactivity toward O-2 decomposition. The Mulliken charge analysis illustrates that, for O-2 adsorption on MgO (001) surface with oxygen vacancies, the electrons are transferred from the substrate to the adsorbed O-2 and occupy the anti-bonding orbital, pi* Of O-2. Thus, the O - O bond strength is weakened. Potential energy curve shows that the energy barrier is considerably decreased for O-2 adsorbed at oxygen vacancy site of MgO(001) surface when compared to that at corner site in our previous study.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2003年第9期815-818,共4页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(29973006和202730313)
结构化学国家重点实验室基金~~
关键词
O2
氧缺陷
镁缺陷
MGO(001)
表面吸附
密度泛函理论
簇模型
O-2
MgO(001) surface
oxygen vacancy
magnesium vacancy
adsorption
density functional theory
cluster models
