【作者】 葛桂贤；

【导师】 罗有华；

【作者基本信息】 河南大学 ， 凝聚态物理， 2007， 硕士

【摘要】 本文利用密度泛函理论研究了不同的过渡金属元素掺杂纯铍团簇的结构及电子性质。其主要内容如下:第一章介绍了团簇科学的研究现状。团簇的尺寸处于原子和宏观体系之间,本身性质具有多样性和奇异性,是实验和理论研究的一个重要对象。首先,简单介绍了团簇的基本性质。接着,从实验和理论两个方面,介绍了团簇研究的基本方法。其中,在实验方法中,介绍了团簇的制备和测量方法。在理论方法中,介绍了团簇研究的基本思路和方法。最后阐明了本论文的主要内容和意义。第二章中,我们简要介绍了密度泛函理论的基本框架和其发展过程。首先,介绍了密度泛函理论的发展过程,从Thomas-Fermi模型,到Hohenberg-Kohn定理,再到Kohn-Sham方程,直到最近的对密度泛函理论的各种修正。介绍了各种常用的交换相关泛函。本章最后介绍基于密度泛函理论的Gaussian软件和DMOL₃软件。第三章研究了MBen（M=Fe、Co、Ni）团簇的结构和电子性质,团簇的生长方式是戴帽式生长,掺杂原子都没有陷进Be原子形成的笼内。对于CoBe_n团簇来说,Co原子的磁矩出现了振荡,当n=6时,Co原子的4s、3d和Be原子的2s、2p较强杂化、Co-Be键长的减小以及对称性的降低导致Co原子的磁矩最小。5和10是团簇的幻数。NiBe_n团簇的几何结构与自旋多重度有关,最低能量结构的自旋多重度是3和1。n≥4时,较强的p, d杂化导致团簇的磁矩淬灭,4是团簇的幻数。对于FeBen团簇,当n=5、7、12时,Fe原子的4s、3d和Be原子的2s、2p较强杂化、Fe–Be键长的减小以及对称性的降低导致Fe原子的磁矩为零。5和10是团簇的幻数。与主团簇相比,掺杂过渡金属Fe、Co、Ni可以增强团簇的稳定性。通过三种掺杂团簇几何结构和电子性质的比较,得出MBen（M= Fe、Co、Ni）（n=2–12）团簇的幻数主要由几何效应来解释。更多还原

【Abstract】 In this thesis, we investigate the geometric, electronic and optical properties of MBen(M=Fe、Co、Ni) clusters using density functional theory (DFT). The main contents are presented as the followings:In Chapter 1, we give a brief introduction to clusters. With a size between those of atoms and macroscopical systems, clusters have many unique properties, and attract much experimental and theoretical research attentions. At first, we introduce the basic properties of clusters. Then, some commonmethods in experimental and theoretical studies on clusters are discussed, including the preparation and detection of clusters, and theoretical studies. Then, research on clusters is reviewed and previewed. At last, we simply describe the purpose and results of our work on clusters.In Chapter 2, we introduce the basic concept and progress of DFT. Development of quantum chemistry promotes the establishment of DFT. Thomas-Fermi model is the first theory using density of electrons as the main variable.Theorem of Hohenberg-Kohn is the fundament of DFT and is developed to Kohn-Sham equation, which can be used to perform real calculations. Now, new corrections and extensions, together with developed exchange-correlation functionals, have made DFT more accurate and suitable for more systems. At the end of this chapter, we introduce the Gaussian and DMOL3 Software.In Chapter 3, we investigate the geometric, electronic properties of MBen(M= Fe、Co、Ni) . The results show that the doped atoms are capped on host clusters and surrounded by Be atoms. The investigated magnetic moments confirm that the Co atomic magnetic moments of CoBen (n=1-12) clusters display an oscillation features. In addition, the Co atomic magnetic moments of CoBe6 is the smallest among all clusters, due to strong hybridization between the 4s, 3d state of Co and 2s, 2p state of Be and short Co-Be average bond distance and low symmetry. It is found that CoBe5 and CoBe10 clusters are more stable than neighboring ones. The geometric structures of NiBen clusters are influenced by spin multiplicities. The magnetic moment of the Ni atom in NiBen clusters is quenching around n≥4, due to strong hybridization between the 4s and 3d states of Ni and the 2s and 2p states of Be. It is concluded that impurity increases the stabilities and the chemical activation of Be cluster. It is found that NiBe4 and NiBe10 clusters are more stable than neighboring ones. The magnetic moment of the Fe atom of FeBen (n=5、7、12) are quenching due to strong hybridization between the 4s, 3d state of Fe and 2s, 2p state of Be and short Fe–Be average bond distance and low symmetry.By contrast to Ben cluster, it is concluded that impurity increases the stabilities of Be cluster. The magic of MBen(M=Fe、Co、Ni) is explained by geometric model, by analyzing the properties of electrons and geometric structure.更多还原