A Charge Density Study of MgCu2 and MgZn2 by the Maximum Entropy Method
A Charge Density Study of MgCu2 and MgZn2 by the Maximum Entropy Method
复制标题
最大熵法研究MgCu2和MgZn2的电荷密度
DOI：
10.7567/jjaps.38s1.456
复制
发表时间：
1999
影响因子：
1.5
通讯作者：
T. Tadaki
中科院分区：
文献类型：
--
作者：
Y. Kubota;M. Takata;M. Sakata;T. Ohba;K. Kifune;T. Tadaki
采用最大熵法（MEM）从同步辐射粉末衍射数据中获得了MgCu 2和MgZn 2的电荷密度分布。在MEM电荷密度中，在MgCu 2的情况下，Cu-Cu原子之间和Zn-Zn原子之间发现重叠的电子密度。这些共价键形成两种化合物的电子kagomé网络。从几何角度考虑，这一特征可以解释为Cu和Zn原子的p3 d3杂化的存在。另一方面，在Mg原子周围没有这种重叠密度，这否认了Mg和Cu之间或Mg和Zn原子之间的任何显著共价性。此外，在所获得的MEM电荷密度中发现了两种化合物的共价键网络的特殊畸变，即共价键向Mg原子移动。这种相当不寻常的键性质应该是由于杂化轨道和带正电的镁离子之间的离子相互作用。对于MgZn 2，发现杂化电子密度的差异与六方堆积序列的Z字形图案有关。
The charge density distributions of the Mg-base Laves phase MgCu2 and MgZn2 were obtained from the synchrotron powder diffraction data by the Maximum Entropy Method (MEM). In the MEM charge density, the overlapped electron densities were found between Cu-Cu atoms in the case of MgCu2 and between Zn-Zn atoms. These covalent bonds form the electronic kagomé network for the both compounds. By the geometrical consideration, this characteristic feature can be interpreted as the existence of p3d3 hybridization of the Cu and Zn atoms. On the other hand, there were no such overlapped densities around Mg atoms, which denies any significant covalency between Mg and Cu or between Mg and Zn atoms. Furthermore, the peculiar distortion of the covalent bond network is found in the obtained MEM charge densities for the both compounds, that is, the covalent bonds are shifted towards the Mg atoms. This rather unusual bond nature should be due to the ionic interaction between the hybridized orbital and positively charged Mg ions. As for the MgZn2, the difference of the hybridized electron density was found related to the zigzag pattern of hexagonal stacking sequence.