Crystal structure of Yb₂CuGe₆ and Yb₃Cu₄Ge₄ and the valency of ytterbium

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• 作者：Sebastian C. Peter ; Udumula Subbarao ; Sumanta Sarkar ; G. Vaitheeswaran ; Axel Svane ; Mercouri G. Kanatzidis
• 关键词：Metal flux technique ; Crystal growth ; X-ray diffraction ; Crystal structure ; Valence ; Electronic structure
• 刊名：Journal of Alloys and Compounds
• 出版年：15 March, 2014
• 年：2014
• 卷：589
• 期：Complete
• 页码：405-411
• 全文大小：2019 K

文摘

The Yb₂CuGe₆ and Yb₃Cu₄Ge₄ compounds were synthesized from reaction mixtures using indium as flux. Both powder and single crystal X-ray diffraction data were used to refine the crystal structures. Yb₂CuGe₆ crystallizes in the monoclinic space group C2/m in the La₂AlGe₆ type structure. The lattice parameters are a = 8.0011(16) 脜, b = 8.1962(16) 脜, c = 10.682(2) 脜 and 尾 = 100.63(3). The crystal structure of Yb₂CuGe₆ can be described as the intergrowth of fragments Ge dimmers and zig-zag Ge chains. Yb₃Cu₄Ge₄ crystallizes in the orthorhombic space group Immm in the Gd₃Cu₄Ge₄ type structure. The lattice parameters are a = 4.1302(8) 脜, b = 6.5985(13) 脜 and c = 13.691(3) 脜. X-ray absorption near edge spectroscopy (XANES) measurements indicate that Yb in Yb₂CuGe₆ and Yb₃Cu₄Ge₄ exists as intermediate and trivalent states, respectively. The structural refinement of Yb₂CuGe₆ is corroborated by total energy calculations within the local density approximation.