Unveiling the role of molecular interactions in crystal morphology prediction

Crystal morphology prediction of two very similar thiadiazoles was performed by means of molecular mechanics calculations embedded in dedicated software. Both thiadiazoles belong to the same orthorhombic space group and differ for the presence of two sulphur and two selenium atoms, respectively. The crystal structures do not present any classic hydrogen bond and the most relevant interactions in the unit cell are some non-covalent π-stacking ones. The results obtained by means of the BFDH method were compared with calculations performed on periodic bond chain (PBC) theory and relative interaction energies. Instead of using only the more traditional force field based calculation, the so called “crystal graph” approach, less demanding in terms of computational time as well as more suitable to describe molecular interactions in details, was used for this purpose. A comparison between the results inferred by means of these two different methods was performed. The potential role of crystallization solvents on faces growth was also discussed.