Structure, optical properties and defects in nitride (III-V) nanoscale cage clusters
Structure, optical properties and defects in nitride (III-V) nanoscale cage clusters
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DOI：
10.1039/b719838h
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发表时间：
2008-01-01
影响因子：
3.3
通讯作者：
Woodley, S. M.
中科院分区：
文献类型：
--
作者：
Shevlin, S. A.;Guo, Z. X.;Woodley, S. M.
报道了笼形结构BN、AlN、GaN和InN亚和低纳米尺寸化学计量团簇的密度泛函理论计算，包括两个八面体家族的T-d和T-h对称性。的结构和能量的确定，我们观察到，BN簇，特别是相对于体相显示出高的稳定性。团簇形成能被证明包括一个常数项，我们归因于曲率能量和形成六个tetraxenes缺陷。发现（BN）60洋葱状双泡结构特别不稳定。相比之下，类似或更大的稳定性，发现为其他氮化物的双壳和单壳笼。的光学吸收光谱已首先由所有化合物的单电子Kohn-Sham轨道能量，之后，我们集中在BN，我们采用了最近开发的时间依赖密度泛函理论的方法。单电子带隙没有表现出强烈的和一致的尺寸依赖性，与量子限制理论的预测不一致。计算了四个最小BN团簇在第一电离势截止能范围内的激发束缚态密度和吸收光谱。通过研究BN团簇的主要点缺陷及其复合物，包括B-N键旋转缺陷、空位、反位和反位，进一步探讨了不同BN团簇的相对稳定性。后者具有最低的形成能量。
Density Functional Theory calculations are reported on cage structured BN, A1N, GaN and InN sub- and low nanosize stoichiometric clusters, including two octahedral families of T-d and T-h symmetry. The structures and energetics are determined, and we observe that BN clusters in particular show high stability with respect to the bulk phase. The cluster formation energy is demonstrated to include a constant term that we attribute to the curvature energy and the formation of six tetragonal defects. The ( BN) 60 onion double-bubble structure was found to be particularly unstable. In contrast, similar or greater stability was found for double and single shell cages for the other nitrides. The optical absorption spectra have been first characterised by the one-electron Kohn-Sham orbital energies for all compounds, after which we concentrated on BN where we employed a recently developed Time Dependent Density Functional Theory approach. The one-electron band gaps do not show a strong and consistent size dependency, in disagreement with the predictions of quantum confinement theory. The density of excited bound states and absorption spectrum have been calculated for four smallest BN clusters within the first ionisation potential cut-off energy. The relative stability of different BN clusters has been further explored by studying principal point defects and their complexes including topological B-N bond rotational defects, vacancies, antisites and interstititials. The latter have the lowest energy of formation.