Comparison of different computational approaches for unveiling the high-pressure behavior of organic crystals at a molecular level. Case study of tolazamide polymorphs

Abstract

The study of the high-pressure behavior of molecular crystals helps find limits of their stabi­lity, as well as obtain previously unknown new phases. This may result in the creation of new materials and their forms for a variety of applications: pharmaceutics, optoelectronics, etc. Nevertheless, until recently, there was no practical unified scheme for high-pressure studies of organic molecules, paying close attention to various inter- and intramolecular interactions. In this work, we compare different computational methods for the high-pressure research of molecular crystals in terms of the energy of particular interactions. Tolazamide polymorphs are taken as a representative system. It is shown that not only «structure-forming» interactions, e.g. H-bonds and stacking interactions, but also multiple van der Waals interactions should be taken into account. Moreover, we compare two different concepts for studying particular H-bonds in terms of absolute and relative energies, showing their importance in understanding the high-pressure behavior of tolazamide polymorphs. Finally, several important details about the high-pressure research of organic crystals at a molecular level by computational methods are formulated.