Modulated Structure of the Composite Crystal Ca0.83CuO2 |
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Authors: | Y Miyazaki M OnodaPP Edwards S ShamotoT Kajitani |
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Institution: | a Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aramaki Aoba, Aoba-ku, Sendai, 980-8579, Japanb School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdomc Advanced Materials Laboratory, National Institute for Materials Science, Namiki, Tsukuba, Ibaraki, 305-0044, Japan |
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Abstract: | We have determined the crystal structure of the quasi one-dimensional cuprate Ca0.83CuO2, known as Ca4Cu5O10, etc., by a superspace group approach. The compound consists of two interpenetrating subsystems of CuO2 chains and Ca atoms. Structural parameters were refined with a superspace group of F2/m(1+α 0 γ)0s using powder X-ray and neutron diffraction data. Lattice parameters were refined to be a1=2.8043(2) Å, b=6.3179(2) Å, c1=10.5744(5) Å, and β1=90.10(1)° for the CuO2] subsystem and a2=3.3652(2) Å, b=6.3179(2) Å, c2=10.5893(5) Å, and β2=93.04(1)° for the Ca] subsystem. Remarkable displacive modulation of the O and Ca atom sites is observed parallel to the b-axis and the c-axis, respectively. On the other hand, the Cu atom sites deviate mainly in the a direction to yield a periodic fluctuation between the nearest Cu-Cu distances. The Ca atoms suitably sit in the center of the modulated O6 octahedra. |
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Keywords: | low-dimensional compound composite crystal superspace group cuprate Rietveld refinement |
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