  Polymorphism offers rich and virtually unexplored space for discovering novel
functional materials. To harness this potential approaches capable of both
exploring the space of polymorphs and assessing their realizability are needed.
One such approach devised for partially ionic solids is presented. The
structure prediction part is carried out by performing local DFT relaxations on
a large set of random supperlattices (RSLs) with atoms distributed randomly
over different planes in a way that favors cation-anion coordination. Applying
the RSL sampling on MgO, ZnO and SnO2 reveals that the resulting probability of
occurrence of a given structure offers a measure of its realizability
explaining fully the experimentally observed, metastable polymorphs in these
three systems.
