Bubbles and microporous frameworks of silicon carbide
Bubbles and microporous frameworks of silicon carbide
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DOI：
10.1039/b902603g
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
Woodley, S. M.
中科院分区：
文献类型：
--
作者：
Watkins, M. B.;Shevlin, S. A.;Woodley, S. M.
报道了密度泛函理论对碳化硅纳米结构的计算结果，包括单团簇、团簇二聚体和纳米孔团簇骨架。我们的结果表明，在纳米尺度上，从Si到C原子之间存在2.5个垂直条形的电荷转移，这导致了纳米碳化硅颗粒采用与氧化锌相同的结构基元，具有T-h，T-d和O对称性的团簇。通过比较光学带隙和电离势，为我们的模型提供了实验支持。除了(SiC)(28)团簇外，T-h或T-d纳米粒子可以结合在四方或六方面上形成动力学稳定的团聚体，对于较大的纳米团簇，四方结合是首选的能量结合，这使得构建不同孔隙率的立方纳米孔骨架成为可能。由较大的簇组成的框架较软；体积模数约为20 GPA，而由较小的簇组成的框架往往较硬。所有骨架的电子结构都可以根据采用的团簇的短程有序来分析，我们预测含有类似于岩盐相的拓扑特征的骨架本质上是金属的。
We report the results of density functional theory calculations on nanostructures of SiC, including single clusters, cluster dimers, and nanoporous cluster frameworks. Our results show that at the nanoscale, there is significant charge transfer of 2.5 vertical bar e vertical bar from Si to C atoms, which results in the adoption of the same structural motifs for nanoparticles of SiC that occur for ZnO, with clusters of T-h, T-d, and O symmetry. Experimental support for our models is provided by comparison of optical gaps and ionisation potentials. With the exception of the (SiC)(28) cluster, the T-h or T-d nanoparticles can bind into kinetically stable agglomerates on either tetragonal or hexagonal faces, with tetragonal binding energetically preferred for larger nanoclusters, which enables the construction of cubic nanoporous frameworks of varying porosities. Frameworks composed of larger clusters are softer; with bulk moduli of ca. 20 GPa while frameworks assembled from smaller clusters tend to be harder. The electronic structure of all frameworks can be analysed in terms of the adopted short-range order of the clusters, we predict that frameworks containing topological features similar to the rock-salt phase are metallic in nature.