摘要
团簇是由几个至上千个原子、分子或离子组成的相对稳定的聚集体,由于其独特的性质而备受重视。团簇结构的研究是团簇其它一切特性研究的基础。在块体研究中,人们已经制成了很多具有非基态结构的块体材料,这些材料往往具有较传统材料更为优异的性能。对于团簇研究而言,人们目前都是把目光集中在具有基态结构的团簇上,但事实上,团簇还有很多非基态结构,有些非基态结构也是非常稳定的。硅材料是电子产业的基石,所以对硅团簇稳态结构的研究具有重要的科学意义和应用价值。
本文用分子动力学的方法,采用Stillinger-Weber势函数,采取不同的初始模型和不同温度条件,获取硅团簇Si n(n=4-35)的稳态结构。我们发现所形成的团簇稳态结构对初始结构和温度非常敏感,初始结构不同、温度不同,得到的硅团簇具有不同的几何构型。一般,原子数目少时所形成的团簇结构较规则,有较好的对称性,并且原子只分布在团簇表面。可以看出原子数大时的团簇,是由原子数目小的团簇拼凑而成的,并且出现了内部原子。形成硅团簇表面的原子多构成空间五边形结构。文章还采用Tersoff势函数,用硅原子替换富勒烯C6 0中碳原子的方法获取了Si 60的结构。
另外,随着纳米机械的发明以及发展,对各个机械部件的力学行为的研究就变得非常迫切。团簇是纳米机械系统最重要的候选部件之一,本文以Si 13团簇为例,对其稳定结构进行了拉伸和压缩的分子动力学模拟,得出了硅团簇拉伸和压缩的力与应变的曲线图。研究表明,在拉伸和压缩的初始阶段力与应变呈线性关系。拉伸时温度越高受力越大,压缩时正好相反,温度越高受力越小,而且同等应变下拉伸时的力明显高于压缩时的力;当拉伸应变达到承载极限,继续拉伸,力突然变的很小,这是因为团簇发生了结构变化。随后接着拉伸,力与应变又呈现出与初始阶段相同的线性关系。
Cluster is the relatively stable aggregates composed by several to thousands of atoms, molecules or irons. It has caught much attention because of its unique properties. The study of structure is the base of the study of all the other characteristics of clusters. In the research of the bulk, people have made out a lot of of bulk materials with non-ground state structure. These materials are often more excellent than the traditional materials. For clusters, people are currently pay more attation on the ground state structures. However, in fact, there are many non-ground state structure,some of which are very stable. Silicon material is the cornerstone of the electronics industry, so the study of the state structures of silicon clusters has important scientific significance and application value.
In this paper, we use the method of molecular dynamics and potential function of Stillinger-Weber for different models and different temperature conditions to obtain the steady-state structures of silicon clusters Sin (n = 4-35). We found the formed steady-state structures of clusters are very sensitive to the initial structure and temperature. The obtained silicon clusters have different geometries for different initial structures and temperature. In general, the formed clusters structure is more regular and better symmetry while the number of atoms is few, and only distributes in the cluster surface. The clusters with large number atoms are pieced by the clusters with small number atoms, and there is internal atoms in this large clusters. The atoms on the surface of silicon clusters often form space pentagon structure. The article also use Tersoff potential function and the method of silicon atoms replacing of carbon atom in the fullerene to obtain the Si6 0 structure..
Furthermore , with the invention and development of nano-mechanics, the study of the mechanical behavior of various mechanical components becomes very urgent.Clusters are one of the most important part candidates of nano-mechanical systems.In this article, we also carry out the molecular dynamics simulation of tension and compression to the stable structure of Si1 3. The reslults show that strength and strain is linear in the initial stage of tension and compression. The force is greater when the temperature is higher in the tension. On the contrary, the force is smaller when the temperature is higher in the compression. The force of tension is significantly higher than the force of compression for the same strain. When the tensile strain reaches the limit load, the force of tension suddenly becomes very small, because clusters structures change. Followed by stretching, the force and strain have shown the same linear relationship in the initial stages.
引文
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