Crystallography of organic energetic materials: thermoelastic properties and equation of state.

Energetic molecular crystals exhibit complex behaviour under extreme conditions of temperature and pressure, which critically influences their performance and safety. However, thermoelastic data remain scattered throughout the literature and are rarely analysed within a unified comparative framework, particularly across multiple classes of energetic materials. In this work, crystallographic data for 16 energetic materials were compiled and systematically analysed to investigate their thermal expansion and equation of state parameters. Thermal expansion coefficients and equation of state parameters were extracted or re-evaluated from experimental variable-temperature and high-pressure diffraction-based crystallographic studies. While volumetric thermal expansion is found to be relatively similar across materials, significant differences in anisotropy are observed, strongly governed by molecular packing and polymorphism. High-pressure data show that most materials exhibit bulk moduli in the range 10-20 GPa, while crystal density appears to influence compressibility, although considerable dispersion exists among materials. These results highlight the central role of crystal structure in controlling thermoelastic behaviour and provide a unified framework linking crystal structure, anisotropy and thermoelastic response in energetic molecular crystals for modelling energetic materials under extreme conditions.