COVALENT GROUP-IV ATOMIC CLUSTERS
COVALENT GROUP-IV ATOMIC CLUSTERS
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DOI：
10.1126/science.235.4791.860
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发表时间：
1987-02-20
期刊：
影响因子：
56.9
通讯作者：
SCHLUTER, M
中科院分区：
文献类型：
--
作者：
BROWN, WL;FREEMAN, RR;SCHLUTER, M
含有两个到几百个原子的原子团簇提供了研究从分子到结晶固体的转变的可能性。共价第四族元素碳，硅和锗现在正在研究这个长期的目标。这些元素特别令人感兴趣，因为它们的晶体固体具有非常不同的性质，而且它们的键合性质介于金属和绝缘体之间。采用脉冲激光技术形成小质量选择原子团簇离子，并采用飞行时间方法对其进行了鉴定。激光光激发被用来研究这些团簇的相对稳定性和它们的碎裂模式。这些模式的Cn+集群，这往往是片段与中性C3的特征损失，被发现是不同的模式的Sin+和Gen+集群，这往往会片段的“魔术”集群，如Si 4+，Si 6+和Si 10+。这些实验结果可以通过最近对小硅和碳团簇的基态结构和稳定性的理论计算来解释。几种理论方法给出了一致的结果，表明小硅团簇是紧凑的，不同于大块晶体的小碎片。计算结果表明，随着团簇尺寸的增大，碳团簇由线性结构向环状结构转变，但存在显著的奇偶性差异。
Atomic clusters containing from two to several hundred atoms offer the possibility of studying the transition from molecules to crystalline solids. The covalent group IV elements carbon, silicon, and germanium are now being examined with this long-range objective. These elements are particularly interesting because of the very different character of their crystalline solids and because they are intermediate between metals and insulators in the nature of their bonding. Small mass-selected atom cluster ions are formed by pulsed laser techniques and identified by time-of-flight methods. Laser photoexcitation is used to study the relative stability of these clusters and their modes of fragmentation. These modes for Cn+clusters, which tend to fragment with a characteristic loss of a neutral C3, are found to be different from the modes for Sin+and Gen+clusters, which tend to fragment to "magic" clusters such as Si4+, Si6+and Si10+. These experimental results can be accounted for by recent theoretical calculations of the ground-state structure and stability of small silicon and carbon clusters. Several theoretical approaches give consistent results, showing that small silicon clusters are compact and different from small fragments of the bulk crystal. Calculations show that carbon clusters change from linear structures toward cyclic structures as the cluster size increases, but with significant odd-even differences.