Electron charge distribution of CaAl_2−x

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• 作者：Karin Sö ; derberg ; Yoshiki Kubota ; Norihiro Muroyama ; Daniel Grü ; ner ; Arisa Yoshimura ; Osamu Terasaki
• 关键词：Intermetallic compounds ; Laves phases ; Charge density ; Maximum entropy method
• 刊名：Journal of Solid State Chemistry
• 出版年：2008
• 出版时间：August 2008
• 年：2008
• 卷：181
• 期：8
• 页码：1998-2005
• 全文大小：1728 K

文摘

Using short wavelength X-rays from synchrotron radiation (SPring-8), high-resolution powder diffraction patterns were collected. In order to study both the structural relationship and the mechanism of stability in the CaAl_2−xZn_x system, among the Laves phases (MgCu₂ and MgNi₂ type) and KHg₂-type structures, the charge density distribution of CaAl_2−xZn_x as a function of x was obtained from the diffraction data by Rietveld analysis combined with the maximum entropy method (MEM). In the MEM charge density maps overlapping electron densities were clearly observed, especially in the Kagomé nets of the Laves phases. In order to clarify the charge redistribution in the system, the deformation charge densities from the densities formed by the constituent free atoms are discussed. In the ternary MgNi₂-type phase, partial ordering of Al and Zn atoms is observed, a finding that is supported by ab-initio total energy calculations.