Polymorph Stability Prediction: On the Importance of Accurate Structures: A Case Study of Pyrazinamide

We reproduce the experimentally observed polymorph stability of the tetramorph pyrazinamide using periodic density functional theory (DFT) calculations augmented with an empirical dispersion term. This was only possible using highly accurate experimental structures, including a model of a disordered polymorph. Further, we demonstrate that a large basis set and very tight integration criteria are needed in the calculations. This study highlights some of the present challenges in crystal structure prediction methods: to obtain sufficiently accurate trial structures and to take into account the possibility of crystal disorder.