【作者】 袁勇波；

【导师】 邓开明；

【作者基本信息】 南京理工大学 ， 材料科学与工程， 2007， 博士

【摘要】 过去的数十年里，团簇研究的发展极其迅速而且成果卓著。这一方面是由于实验技术的不断提高，使得不同尺寸的团簇制取和其物理性质的研究变得容易；另一方面，计算机和计算技术的迅速发展，使得较小团簇的原子组态和电子结构从第一性原理进行从头计算以及对它们进行动力学计算机模拟成为可能。研究团簇的几何构型、团簇的性质如何随着原子数的增长而改变、团簇的成键作用、电子结构等等，从而进一步揭示团簇的物理化学性质，构成了当今团簇物理学研究的一些中心主题。近几年，过渡金属碳化物团簇（met-cars）的研究是科学界一个比较热门的研究课题，因为这些材料被期望会具有许多不同与普通材料的化学和物理特性，有望在材料科学、微电子学、纳米技术、催化学以及固体化学方面会具有比较好的应用前景。而富勒烯团簇的研究是纳米科技中的一个重要组成部分。通过掺杂的方式可以改变富勒烯的物理和化学性质，从而得到我们所需要的功能材料。这些正激发人们将越来越多的热情投入到对团簇的研究之中本文主要采用密度泛函理论（DFT），对过渡金属碳化物以及掺杂富勒烯等团簇体系进行理论计算研究，内容分为以下几个部分：第一章简要介绍了团簇领域的发展现状和发展前景。第二章介绍了量子化学计算的发展历史和现状，重点介绍了密度泛函理论，以及常用的从头计算软件包。这些是我们进行团簇研究的理论基础和计算工具。第三章主要介绍了对原子小团簇的研究工作。在这部分，我们从第一性原理出发，应用密度泛函理论，分别系统地研究了MC₂（M=V、Cr、Fe和Co）、MC₃（M=Sc、V和Cr）、TiC₅和SiN团簇的中性分子和阴离子的性质，计算了它们的平衡构型、电子组态和电子亲和势等。另外，我们还应用了含时密度泛函的方法计算了这些团簇的低能激发态性质，并对实验的阴离子光电子能谱（PES）进行了理论指认。我们的计算结果与已知的实验数据相比符合得非常好。这说明含时密度泛函理论作为一种有力的理论研究工具，可以在理论上对团簇系统的低电子激发态性质作出令人信服的预测。第四章介绍了对C₅₉B^-和C₅₉N⁺的几何结构和电子结构所进行的系统研究工作。尽管替代性掺杂富勒烯C₅₉B^-和C₅₉N⁺与经典的富勒烯分子C₆₀是等电子类似物，但是我们发现由于掺杂原子的加入，富勒烯的电子结构属性已经发生了非常大的变化。掺杂原子给整个体系带来了杂质能级，使得B原子在C₅₉B^-中担任空穴的角色，而N原子在C₅₉N⁺中担任施主的角色。局部态密度图显示掺杂原子与碳笼子的碳原子之间存在着轨道交叠。更多还原

【Abstract】 In the past decades, research on clusters has been one of the largest as well as themost rapidly developed branches of physics. Taking advantage of rapid progress in theexperimental technology, it is much readily to produce clusters with different size and tostudy their physical properties; on the other side, the development of computer andalgorithms make it possible that we can carry out first-principles calculations to obtainthe geometry and the electronic structure of the small clusters and to simulate thedynamics. Nowadays, in this branch, the focus issues are to study the geometry, bonding, and electronic structure properties, to observe how the properties change with incrementof its size, and to discover more novel physical and chemical properties. The calculationsabout clusters are the subjects of this dissertation.Transition metal carbide clusters （met-ears） have been a subject of intenseinvestigation in recent years due to their promising applications in materials sciences, microelectronies, nanotechnology, catalysis, solid state chemistry, and so on. And thestudy of fullerenes is one important part of nanotechnology. We can change the physicaland chemical properties of fullerenes to get the material that we need by doping. All ofthose arouse people’s enthusiasm for the study of clusters.In this dissertation, using the density functional theory （DFT） we mainly investigatethe met—cars and heterofullerenes clusters. The dissertation is divided into the followingfour chapters.In Chapter 1, the actuality and development of cluster researching are introducedbriefly.In Chapter 2, the history and actuality of quantum chemistry computation are brieflyintroduced, and we mainly describe the density functional theory （DFT） as well as somepopular ab initio software packages, which are our theoretical foundations andcomputational implements to deal with cluster system.In Chapter 3, the works concentrate on the study of small clusters. In this part, density functional calculations are performed to study MC₂ （M=V, Cr, Fe and Co）, MC₃（M=Sc, V and Cr）, TiC₅ and SiN clusters in their neutral and anionic states. Theequilibrium geometries, electronic configurations and electron affinities of these clusters are obtained. Time-dependent DFT （TDDFT） is used to calculate the excited states. Atheoretical assignment for the features in the experimental photoelectron spectrum isgiven. Our results compare well with the available experimental results, and show thatTDDFT can give the convincing prediction for the excited state properties of clusters.In Chapter 4, the study on the structural and electronic properties of C₅₉B^- andC₅₉N⁺ is described. Though the C₅₉B^- and C₅₉N⁺ are isoelectronic analogues to C₆₀, it isfound that doping induces great changes in electronic properties. The doped atoms bringon impurity energy levels and make B in C₅₉B^- and N in C₅₉N⁺ act as a hole and anelectron donor respectively. The PDOSs （partial densities of states） indicate thehybridization between the orbitals of the doped atoms and of the carbon atoms of thecages.更多还原