Experimental and Theoretical Charge Density Studies at Subatomic Resolution
Experimental and Theoretical Charge Density Studies at Subatomic Resolution
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DOI：
10.1021/jp2050405
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发表时间：
2011-11-17
影响因子：
2.9
通讯作者：
Iversen, B. B.
中科院分区：
文献类型：
--
作者：
Fischer, A.;Tiana, D.;Iversen, B. B.
对金刚石和硅的精确实验和理论结构因子的分析表明，由于共价键的形成，核壳的收缩引起了总电荷密度的显着扰动，这在精确的电荷密度研究中是不可忽视的。我们概述了利用扩展的Hansen-Coppens多极模型进行的实验研究可以分析核心收缩/膨胀和核心极化现象的性质和起源。忽略或不充分地处理这些亚原子电荷密度现象可能会产生错误的热位移参数和多极精修中的高剩余密度。因此，我们的详细研究表明，所有原子壳层的收缩/膨胀和布居参数的改进对于用多极模型精确地重建电子密度分布是至关重要的。此外，我们的结果还表明，还需要采用内层的极化，特别是在第二排甚至更重的元素参与共价键的情况下。这些理论研究得到了从第三代同步辐射光源(Spring-8，BLO2B2)获得的钻石X射线粉末衍射数据的直接多极修正的支持。
Analysis of accurate experimental and theoretical structure factors of diamond and silicon reveals that the contraction of the core shell due to covalent bond formation causes significant perturbations of the total charge density that cannot be ignored in precise charge density studies. We outline that the nature and origin of core contraction/expansion and core polarization phenomena can be analyzed by experimental studies employing an extended Hansen-Coppens multipolar model. Omission or insufficient treatment of these subatomic charge density phenomena might yield erroneous thermal displacement parameters and high residual densities in multipolar refinements. Our detailed studies therefore suggest that the refinement of contraction/expansion and population parameters of all atomic shells is essential to the precise reconstruction of electron density distributions by a multipolar model. Furthermore, our results imply that also the polarization of the inner shells needs to be adopted, especially in cases where second row or even heavier elements are involved in covalent bonding. These theoretical studies are supported by direct multipolar refinements of X-ray powder diffraction data of diamond obtained from a third-generation synchrotron-radiation source (SPring-8, BLO2B2).