【作者】 附青山；

【导师】 涂铭旌；

【作者基本信息】 四川大学 ， 纳米材料与纳米技术， 2007， 硕士

【摘要】 近些年金属原子团簇引起了研究者极大的兴趣，因为它们除了对很多技术工艺产生了直接的影响，还表现出了许多在其他元素的团簇中未被发现的新奇的特点和现象。例如：这其中之一就是中性金属原子团簇中结合键随着原子数的增加而发生转变的现象。事实上小的金属团簇常常不具备金属状态下所具有的一些金属特性。随着原子数的增加，这些性质才逐步的表现出来。这些转变是单一的吗?这些转变有一定的尺寸范围吗?对于这些问题的回答都是非常粗略的，因为这个现象是非常复杂的、多重性的，而且涉及到团簇很多的性质。因此，要研究这个转变明显的开始或表现就依赖于对团簇性质的研究。金属镁团簇非常适合用来研究金属团簇的随原子数增加的金属性转变行为。两个原子的镁团簇表现出来较弱的范德华键合，而随着镁原子数的增加逐步表现出更强的键合。本文利用Gaussian03程序对Mg_n(n=2-8)，Mg_nLa(n=2-6)和Mg_nTi(n=2-6)团簇可能的几何拓扑结构进行了计算和优化，给出了它们最稳定的几何构型。同时计算了团簇的总能量、总能量的二阶差分、每个原子的平均束缚能、平均键长、最高占据轨道和最低非占据轨道之间的能隙，利用这些量随镁原子数的增加而呈现的变化分析了团簇的稳定性、能级特点、团簇得失电子的能力以及团簇中金属性的转变。最后对Mg_n(n=2-8)团簇和加入钛、镧原子后的团簇进行了比较。结果表明镧、钛原子的加入对镁团簇的稳定几何构型的改变并不明显；由于镧、钛原子的外层电子的排布与镁原子有很大的差异，它们的加入使得镁团簇的稳定性、得失电子的能力、化学活性都发生了很大的变化。我们的结论，为具体实验中制备、研究镁团簇以及镁的混合团簇提供了一些理论上的参考。更多还原

【Abstract】 Metal clusters,or more precisely, atomic clustersof elements that are metals in bulk quantities,form an area of special interest.Apart from the direct relevance to many technologies,they exhibit a host of novel features and phenomena not found in chusters of other elements.One of these is the change in the nature of bonding as a function of the cluster size.In fact,small atomic clusters of metallic elements may altogether lack characteristics usually associated with the metallic state.These characteristics then grow in as the clusters grow in size.Is the transition to metallicity monotonic ro not?What is the typical size or size-range at which it takes place?The Phenomenon is complex and multifaceted because different properties evolve differently with size.Therefore,the apparent onset and manifestations of the transition may depend on the property studied.Magnesium is especially appropriate for the investigation of the size-diduced transition to metallicity.Whereas the diatomic molecule of magnesium clusters of larger sizes exhibit strong bonding.This paper studied Mg_n(n=2-8), Mg_nLa(n=2-6) and Mg_nTi(n=2-6) clusters, computed and optimized the geometric structures of these clusters.Meanwhile we computed the energy, the bing energy of every atom, average bond and the gap of HOMO and LUMO, then we analysed the stability, the capability of getting or losting electrons and the translation to the metallic state.Finally we compared Mg_n(n=2-8) with Mg_nLa(n=2-6) and Mg_nTi(n=2-6) clusters,got some conclutions.The results indicate that there aren’t obvious changes of the structures of Mg clusters as adding La or Ti atoms jito them,but it will cause notable changes of the stability and capability of getting or losting electrons.We hope our work will help to study Mg clusters and their mixed clusters by supporting some theoretic suggestions.更多还原