Structure analysis of mutually incommensurate composite crystal (Ca 0.5Y 0.5) 0.80CuO 2

Abstract

Single-crystal X-ray structure analysis of mutually incommensurate (Ca 0.5Y 0.5) 0.80CuO 2, “Ca 2Y 2Cu 5O 10” has been performed by the composite approach which leads to average substructures and their relative arrangement. The composite crystal structure of (Ca 0.5Y 0.5) 0.80CuO 2 has the CuO 2 substructure and the Ca 0.5Y 0.5 substructure. The CuO 2 substructure with a 1 = 10.598(2) Å, b = 6.189(2) Å, c 1 = 2.825(2) Å, β 1 = 90.19(4)°, V 1 = 185.4(1) Å 3, Z = 4 and space group F2/ m has the plane of edge-shared one-dimensional CuO 2 chains along the c-axis. The Ca 0.5Y 0.5 substructure with a 2 = 10.629(2) Å, b = 6.189(2) Å, c 2 = 3.517(1) Å, β 2 = 94.36(3)°, V 2 = 230.7(1) Å 3, Z = 4 and space group F2/ m forms the sheet of (Ca, Y) atoms in the ac-plane. By considering (3 + 1)-dimensional superspace group symmetry, it is concluded that the incommensurate composite crystal structure of (Ca 0.5Y 0.5) 0.80CuO 2 should be described by the combination of F2/ m for the CuO 2 substructure and F2/ c for the Ca 0.5Y 0.5 substructure. The composite approach has made clear that the plane of CuO 2 chains and the sheet of (Ca, Y) atoms stack alternately to form a mutually incommensurate composite crystal with layered substructures.