On the structure of Si(100) surface: importance of higher order correlations for buckled dimer.
On the structure of Si(100) surface: importance of higher order correlations for buckled dimer.
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DOI：
10.1063/1.4807334
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
S. Back;J. Schmidt;Hyunjun Ji;Jiyoung Heo;Y. Shao;Yousung Jung
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文献类型：
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作者：
S. Back;J. Schmidt;Hyunjun Ji;Jiyoung Heo;Y. Shao;Yousung Jung
我们重新审视了一个悬而未决的理论问题，即Si（100）表面的表面重构是否会在0 K时在本征势能面上产生对称或屈曲的二聚体。这个看似简单的问题仍然没有明确的答案，因为所有现有的基于密度泛函的计算预测的二聚体被屈曲，而大多数基于波函数的相关处理更喜欢对称的配置。在这里，我们使用双杂化密度泛函（DHDF）的几何优化，特别是，XYGJ-OS，完整的活性空间自洽场理论，多参考微扰理论，多参考组态相互作用（MRCI），MRCI与戴维森校正（MRCI + Q），多参考平均二次CC（MRAQCC），和多参考平均耦合对泛函（MRACPF）方法来解决这个问题。当在DHDF优化的几何结构上使用CASPT 2方法时，对称二聚体的能量仍然低于屈曲二聚体，这与使用B3 LYP几何结构的先前结果一致[Y.荣格，Y。Shao，M. S. Gordon，D. Doren和M. Head-Gordon，J.Chem.Phys.119，10917（2003）]。然而，有趣的是，MRCI + Q、MRAQCC和MRACPF的结果（对电子相关效应给出了更精确的描述）表明，屈曲的二聚体比对称的二聚体稍微更稳定。本研究强调了在探索重构Si（100）表面的极其精细的势能面时，精确描述电子-电子关联以及适当的多参考波函数的重要性。
We revisit a dangling theoretical question of whether the surface reconstruction of the Si(100) surface would energetically favor the symmetric or buckled dimers on the intrinsic potential energy surfaces at 0 K. This seemingly simple question is still unanswered definitively since all existing density functional based calculations predict the dimers to be buckled, while most wavefunction based correlated treatments prefer the symmetric configurations. Here, we use the doubly hybrid density functional (DHDF) geometry optimizations, in particular, XYGJ-OS, complete active space self-consistent field theory, multi-reference perturbation theory, multi-reference configuration interaction (MRCI), MRCI with the Davidson correction (MRCI + Q), multi-reference average quadratic CC (MRAQCC), and multi-reference average coupled pair functional (MRACPF) methods to address this question. The symmetric dimers are still shown to be lower in energy than the buckled dimers when using the CASPT2 method on the DHDF optimized geometries, consistent with the previous results using B3LYP geometries [Y. Jung, Y. Shao, M. S. Gordon, D. J. Doren, and M. Head-Gordon, J. Chem. Phys. 119, 10917 (2003)]. Interestingly, however, the MRCI + Q, MRAQCC, and MRACPF results (which give a more refined description of electron correlation effects) suggest that the buckled dimer is marginally more stable than its symmetric counterpart. The present study underlines the significance of having an accurate description of the electron-electron correlation as well as proper multi-reference wave functions when exploring the extremely delicate potential energy surfaces of the reconstructed Si(100) surface.