One-dimensional diffuse scattering of 1,3-di(tert-butyl)cyclopentadienyl pentaphosphaferrocene modelled with closed-form expressions

Abstract

1,3-di(tert-butyl)cyclopentadienyl pentaphosphaferrocene (Cp′′FeP5) crystallizes as polytypes, where adjacent layers are related by either a c- or an n-glide reflection. In the simplest possible polytypes only one kind of glide reflections is realized, leading to overall Pca21 or Pna21 symmetry respectively. Crystals isolated from the same crystallization experiment feature a varying degree of stacking disorder. One-dimensional diffuse scattering of a crystal with particularly strong disorder was modelled with closed-form expressions derived from a growth model. A range of interaction of s = 2 was necessary to satisfactorily describe the observed diffraction intensities. The crystal can be described as a disordered analogue of an allotwin, that is an intergrowth of the Pca21 or Pna21 polytypes with a distinct preference for the former.