However, crystal structure solution from thin films is not a routine technique, and is normally only necessary when a surface-mediated polymorph is present for which single crystals cannot be grown.9 There are many difficulties associated with crystal structure solution from a thin film, primarily the indexation of diffraction patterns and the observation of a sufficient amount of data (often only a small number of Bragg peaks are observed). Extraction of reliable peak intensities, normally crucial for structure solution, is also challenging due to the strong influence of crystalline texture on the diffracted intensities.13–15 Recently, a method has been developed combining molecular dynamics (MD) simulations with grazing incidence X-ray diffraction (GIXD) data which only requires data sufficient to index and obtain a unit cell; this approach was recently used to solve the thin film structure of the hydrogen-bonded pigment Tyrian purple.10 A similar approach to the thin film crystal structure solution of EPI is taken here.