Terauchi Masami, Morito Haruhiko, Yamane Hisanori, Koshiya Shogo, Kimoto Koji
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
Microscopy (Oxf). 2018 Mar 1;67(suppl_1):i72-i77. doi: 10.1093/jmicro/dfx132.
Chemical bonding state of sodium borosilicide Na8B74.5Si17.5, which is a new member of B12-cluster materials, is investigated by soft X-ray emission spectroscopy. The material is composed of B12 cluster network and characteristic silicon chains of [-Si-(Si-Si)3-Si-] connected by sp3 bonding, in which bonding distances and bonding angles are close to those in cubic Si crystal. B K-emission spectrum of the material showed a similar but a broader intensity distribution with those of B12 cluster materials of α-r-B, B4C and β-r-B. The broader intensity distribution can be due to a variation of B-B bond length in B12 cluster. The density of states (DOS) of silicon chains of [-Si-(Si-Si)3-Si-] was experimentally derived. It shows a similar energy width, and peak or shoulder structures in intensity distribution with those of L-emission spectrum of cubic Si. From comparisons between experimental spectra and corresponding calculated DOS, covalent bonding between Si chain and B12 cluster network is suggested. Those are discussed by using a theoretically calculated density of state of Na8B74.5Si17.5 by using WIEN2k code.
通过软X射线发射光谱研究了硼硅酸钠Na8B74.5Si17.5的化学键合状态，它是B12簇材料的一个新成员。该材料由B12簇网络和通过sp3键连接的[-Si-(Si-Si)3-Si-]特征硅链组成，其中键长和键角与立方Si晶体中的相近。该材料的B K发射光谱与α-r-B、B4C和β-r-B的B12簇材料的光谱显示出相似但更宽的强度分布。更宽的强度分布可能是由于B12簇中B-B键长的变化。实验得出了[-Si-(Si-Si)3-Si-]硅链的态密度（DOS）。它显示出与立方Si的L发射光谱相似的能量宽度以及强度分布中的峰或肩结构。通过实验光谱与相应计算的DOS之间的比较，表明Si链与B12簇网络之间存在共价键合。利用WIEN2k代码对Na8B74.5Si17.5的理论计算态密度对这些进行了讨论。
