$n$-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.

中文翻译：

---

非周期性尿素包裹体晶体中烷烃亚结构准液相的短程有序

$n$-烷烃/脲包合物是非周期性晶体的典型例子，其具有均匀排列的烷烃客体分子，包含在由超分子脲主体形成的线性通道内。在这里，我们研究了短链客体分子（从辛烷到十二烷）以尖锐层的形式存在的单晶漫散射。这些层内漫散射的强调制表明烷烃分子在相邻通道中的位置是相关的。使用三维差分对分布函数方法，我们提取了有效相互作用势，并表明相互作用是由尿素分子的弛豫介导的。