The structure of Li3Cu2O4, a compound with formal mixed valence

The structure of Li3Cu2O4 was solved from X-ray powder diffraction data and refined from a multiphase specimen using the Rietveld method. The cuprate crystallizes in C2/m with Z = 2. The compound has a small homogeneity range. Typical parameters are a = 9.946(5) A, b = 2.778(2) A, c = 7.260(5) Aand β = 119.10(2)°. The structure may be described as an ordered intergrowth of slabs of Li2CuO2 and hypothetical LiCuO2 of NaCuO2 type. The formula suggests a copper(II, III) mixture, but there is only one crystallographic copper site which implies a more appropriate formulation as Li3+[Cu(II)O2]232 with parallel strands of edge-coupled CuO4 units running along the b axis.