Division of Physics, Faculty of Pure and Applied Sciences, Center for Integrated Research in Fundamental Science and Engineering &Tsukuba Research Center for Interdisciplinary Materials Science, University of Tsukuba. 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8571, Japan.
Sci Rep. 2017 Jan 25;7:41375. doi: 10.1038/srep41375.
Charge densities of iso-structural metal hexaborides, a transparent metal LaB and a semiconductor BaB, have been determined using the d > 0.22 Å ultra-high resolution synchrotron radiation X-ray diffraction data by a multipole refinement and a maximum entropy method (MEM). The quality of the experimental charge densities was evaluated by comparison with theoretical charge densities. The strong inter-octahedral and relatively weak intra-octahedral boron-boron bonds were observed in the charge densities. A difference of valence charge densities between LaB and BaB was calculated to reveal a small difference between isostructural metal and semiconductor. The weak electron lobes distributed around the inter B octahedral bond were observed in the difference density. We found the electron lobes are the conductive π-electrons in LaB from the comparison with the theoretical valence charge density. We successfully observed a spatial distribution of electrons near the Fermi level from the X-ray charge density study of the series of iso-structural solids.
采用多极精修和最大熵法（MEM），利用 d＞0.22 Å 的超高分辨率同步辐射 X 射线衍射数据，测定了等结构金属六硼化物、透明金属 LaB 和半导体 BaB 的电荷密度。通过与理论电荷密度的比较，评估了实验电荷密度的质量。在电荷密度中观察到了强烈的八面体间和相对较弱的八面体内部硼-硼键。计算了 LaB 和 BaB 之间的价电荷密度差，以揭示等结构金属和半导体之间的微小差异。在差密度中观察到围绕 B 八面体键分布的弱电子叶。通过与理论价电荷密度的比较，我们发现电子叶是 LaB 中的导π电子。我们成功地从一系列等结构固体的 X 射线电荷密度研究中观察到费米能级附近电子的空间分布。
