Structure of KNbOB2O5 – a commensurately modulated structure

Abstract

Members of the AMOB2O5 (A = K, Rb, Cs, Tl; M = Nb, Ta) family of compounds can be described as modulated structures with a single superspace group and very similar modulation functions. Single-crystal X-ray diffraction data (Mo Kα radiation) are used to solve and refine the structure of KNbOB2O5 in these terms for the first time. The average structure is solved and refined in the space group Pmn21. Subsequently, the atomic modulation functions are determined using JANA2000 and superspace-group symmetry Pmn21(0,0.375,0)s. The commensurately modulated structure is finally refined as a superstructure in the space group Pbn21 using SHELXS97 converging to R 1 = 0.024.