Pair distribution function analysis of molecular compounds: significance and modeling approach discussed using the example of p-terphenyl

Modeling the pair distribution function (PDF) of molecular compounds is a challenging task because intra- and intermolecular interactions lead to very different features in the PDF. This article discusses the different peak shapes in PDFs of molecular compounds in detail. Moreover, the common methods to calculate PDFs from structural models are summarized and evaluated with respect to molecular systems and an approach to calculate PDFs from molecular crystals more accurately is introduced. p-Terphenyl was chosen as a test compound. It adopts a crystal structure with disordered features and short-range order. The short-range order was previously investigated by analyzing single-crystal diffuse scattering and it was also extracted from experimental PDFs during this study.