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  Breternitz, J.; Schorr, S.: Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc2₁. Acta Crystallographica Section A 77 (2021), p. 208-216

10.1107/s2053273320015971
Open Access Version

Abstract:
Binary III-V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials for optoelectronic properties, amongst others. With rising concerns over the utilisation of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallising in lower-symmetry variants of wurtzite. Herein, we present the symmetry relationships between these structural types specific to nitrides and oxide nitrides and update some prior work on this matter. The non-existence of compounds crystallising in Pmc21, the formally highest subgroup of the wurtzite-type fulfilling Pauling’s rules for 1:1:2 stoichiometries has been stunning scientists for a while and we rationalise from a crystallographic basis, why this space group is unlikely to be adopted.