halogen bond has been reported by O. Hassel in 1954, the field remained largely unexplored until the last two decades. The recent increased interest in halogen bonding is attributed to the promising functional properties of halogen bonded cocrystals in pharmaceutical solids, polymers, luminescent materials, optical materials, and others. Mechanochemical methods offer a clean and efficient way to for synthesising halogen-bonded Fig. Molecular diagram of the components used in the crystallisation experiment. cocrystals and performing their interconversions. However, it is always desirable to predict the possible products prior to experimental synthesis. With this in mind, we have recently used periodic density-functional theory (DFT) calculations and dissolution calorimetry measurements to predict the interconversion of halogen-bonded cocrystals via mechanochemical exchange of donor and acceptor components. This was the first example of a combined use of periodic DFT and dissolution calorimetry to explore the thermodynamics of solid-state transformations of binary halogen and hydrogen-bonded cocrystals. The excellent accuracy of periodic DFT calculations in predicting the reaction energies was demonstrated, highlighting the opportunities presented by this approach in predicting the solid-state reactivity of halogen-bonded materials from first principles.