LSDA+U方法对富勒烯内掺稀土原子的结构和电子结构的理论研究

LSDA+U STUDY ON RARE EARTH DOPED ENDOHEDRAL FULLERENE

在密度泛函理论框架下的局域密度近似方法 (LDA)能够准确地给出广延态电子体系的基态电子结构 ,是研究复杂体系的电子结构的一种非常成功的方法。由于这种方法不含参数 ,被广泛地用于微观体系的研究。但是 ,在处理的体系中含有局域电子时 ,由于方法的局限 ,给出的结果与光电子谱等试验结果符合得并不好。LSDA +U方法是在局域自旋密度近似的框架下 ,结合模型哈密顿方法 ,对局域电子采用哈伯德模型描述 ,用以改进局域密度近似计算的一种方法。本文利用局域密度近似下的离散变分团簇方法 (DVM )对于内嵌稀土原子的富勒烯Er2 @C82 、Tm @C82 的电子结构进行了第一性原理的计算。对于体系中所含的稀土原子存在强关联的 4f电子 ,在LDA方法计算的基础上 ,考虑 4f电子在位库仑作用 ,用LSDA +U方法研究了上述体系 ,得到了可以和XPS和吸收谱相比较的结果。

Local density functional is successful in dealing with the complex system. It can give accurate properties of ground states of delocalized systems.As an ab intio method, it is used extensively in studying electronic structures of complex systems. But when there are d or f electrons in the system, LDA fails to give results that can be compared with photoelectron spectra. LSDA+U method is based on the frame work of density functional theory and adopts the Hubbard model to describe the localized electrons. It can deal with systems where both delocalized and localized electrons coexist. In this paper, the electronic structures of endohedral fullerenes Er 2@C 82 , and Tm@C 82 are studied by ab initio Discrete Variation cluster method. To deal with the localized 4f electrons of rare earth atoms, LSDA +U calculations are carried out. Geometry of these systems is optimized and the electronic structures of these trapped lanthanide atoms are investigated.