组装氢化硅团簇构建硅纳米管
Constructing silicon nanotubes by assembling hydrogenated silicon clusters
摘要：
近年来，寻找或设计与碳类似的硅纳米结构引起了人们极大的兴趣。在这项工作中，密度泛函计算进行系统地研究了一系列有限和无限氢化簇组装的硅纳米管（SiNTs）。研究发现，氢化类富勒烯硅团簇$Si_{4m}H_{4m}$通过适当的组装可以得到稳定的一维SiNTs，分子式为$Si_{m(3k+1)}H_{2m(k+1)}$.稳定性首先由大的内聚能和HOMO-LUMO能隙证明。在所有这样的硅纳米管中，由$Si_{20}H_{20}$（$m=5$）和$Si_{24}H_{24}$（$m=6$）构建的硅纳米管是最稳定的，这是由于在这些结构中硅键角最接近本体$sp^{3}$类型。热稳定性分析进一步证实了这种管在室温下可以很好地存在。最后，有限纳米管和无限纳米管都显示出大的能隙。随着管半径的增加，出现了直接-间接-直接的带隙转变。直接带隙的存在可能使它们成为电子和光电子器件的潜在构建块。
英文摘要：
The search or design of silicon nanostructures similar to their carbon analogues has attracted great interest recently. In this work, density functional calculations are performed to systematically study a series of finite and infinite hydrogenated cluster-assembled silicon nanotubes (SiNTs). It is found that stable one-dimensional SiNTs with formula $Si_{m(3k+1)}H_{2m(k+1)}$ can be constructed by proper assembly of hydrogenated fullerene-like silicon clusters $Si_{4m}H_{4m}$. The stability is first demonstrated by the large cohesive energies and HOMO-LUMO gaps. Among all such silicon nanotubes, the ones built from $Si_{20}H_{20}$($m=5$) and $Si_{24}H_{24}$($m=6$) are the most stable due to the silicon bond angles that are most close to the bulk $sp^{3}$ type in these structures. Thermostability analysis further verifies that such tubes may well exist at room temperature. Finally, both finite nanotubes and infinite nanotubes show a large energy gap. A direct-indirect-direct band gap transition has been revealed with the increase of the tube radius. The existence of direct band gap may make them potential building blocks for electronic and optoelectronic devices.
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