$n$-alkane/urea inclusion compounds are prototypical examples of aperiodic crystals with uniformly aligned alkane guest molecules contained within linear channels formed by the supramolecular urea host. Here, we investigate single-crystal diffuse scattering, which is present in the form of sharp layers, from short-chain guest molecules (from octane to dodecane). The strong modulation of diffuse scattering within these layers shows that the positions of alkane molecules in neighboring channels are correlated. Using the three-dimensional difference pair distribution function method, we have extracted the effective interaction potentials and have shown that the interaction is mediated by the relaxation of urea molecules.

• Received 1 December 2021
• Accepted 25 April 2022

DOI:https://doi.org/10.1103/PhysRevB.106.054206