Structural investigations of new copper fluorides NaRECu2F8 (RE3+=Sm3+, Eu3+, Gd3+, Y3+, Er3+, Yb3+)

Abstract

A series of copper(II) and rare earth fluorides has been prepared. The crystal structure of NaGdCu ₂ F ₈ has been solved from single crystal data and refined to conventional R=0.028 (wR=0.048) for 585 independent reflections. The symmetry is tetragonal (space group I422) with a=5.407(1) and c=10.382(1) Å (Z=2). A Rietveld analysis of NaYCu ₂ F ₈ and refinements of the powder X-ray diffraction data for the other compounds of the series confirmed the I422 space group. The structure consists of layers of CuF ₄ square-planes perpendicular to the c-axis, interleaved alternatively by Na ⁺ or RE ³⁺ cations located in antiprisms.