O2在MgO(001)完整和缺陷表面上的吸附

在密度泛函理论的框架下， 采用嵌入点电荷簇模型研究了O2在MgO(001)完整和缺陷表面上的吸附.用电荷自洽的方法确定了点电荷的值.计算结果表明， O2倾向吸附在低配位的角Mg2＋端.并且发现， 当O2为平躺吸附时，键长有较大的拉伸，将有利于O2的解离.同时，分别计算了使用裸簇和嵌入表观±2.0 e点电荷簇模型时的吸附能，并与采用电荷自洽方法的计算值进行了比较.结果表明，电荷自洽方法更能有效反映簇周围的环境，得到的计算结果能够较好地与实验值吻合.最后，分别计算了不同吸附情况下O2的振动频率.

Theoretical Study of O2 Adsorption on Perfect and Defect Sites of MgO(001) Surface

The adsorption of O2 on the perfect and low coordinated sites of MgO(001) surface has been studied with the finite cluster models embedded in a large array of point charges by density functional method. The point charge value was determined by self consistence technique. Different kinds of possible models of O2 adsorbed on MgO(001) surface were calculated. The optimization of the geometry, calculation of the adsorption energy, vibrational frequency and analysis of the Mü lliken population to those adsorption models were carried out. The results indicate that cationic site in the lowest coordinated corner is the most advantageous position for O2 adsorbed on MgO(001) surface. The O- O bond strength is considerably weakened when O2 lies flatly on the Mg atom at the corner(Mg3c). The calculated adsorption energy of O2 on MgO(001)perfect surface is in good agreement with experimental value. For O2 adsorbed on the perfect surface embedded in nominal ± 2.0e point charges and on perfect surface using the bare cluster, the adsorption energies given in this paper show that they have a large deviation from the experimental value. The vibrational frequency of adsorbed O2, which is experimentally difficult to measure due to the existence of isotope exchange, was also calculated.