The examples of the composition-ordering wave in the IMS KNd(Mo)₄)₂ (front plan), Bi₂(Mo0₄)₃ (middle plan) and La₂(Mo0₄)₃ (back plan)

Capabilities and limitations of a (3 + d)-dimensional incommensurately modulated structure as a model for the derivation of an extended family of compounds: example of the scheelite-like structures

Acta Cryst. (2008). B64, 12-25 [doi:10.1107/S010876810705923X]

Incommensurately modulated structures (IMSs) are described in superspace. The resulting non-periodic structure is obtained from a 3D cut of the higher dimensional periodic description of the IMS. The superspace model consists of a basic structure on which a modulation is applied. The present article illustrates a novel application of the superspace concept, namely the possibility to describe a large series of compounds uniquely based on the basic structure used to describe the IMS on which we apply different modulation functions. This method is illustrated with the example of the Scheelite family consisting of both 3D-periodic and IMS cases. The proposed model can act as a common (3+1)D structure type from which all the possible structures can be attributed.