Vibrational modes in the Pmc21 structure of ZnGeN2

•Phonons and related Raman spectra are presented for a not yet discovered crystal structure of ZnGeN2.•This may facilitate its experimental confirmation in future experimental work.

Vibrational normal modes at the Brillouin zone center and related Raman and infrared spectra are calculated from first-principles density functional perturbation theory for the until now hypothetical Pmc21 structure of ZnGeN2 and are compared with those in the known Pnb21 structure. Although there are great similarities in phonon spectra, we show that the distinctions are specific enough to experimentally distinguish the two crystal structures.