Phonon and phonon-related properties of MgSiN2 and MgGeN2 ceramics: First principles studies

In this work, we used density functional perturbation theory to calculate phonon frequencies, phonon dispersions, Born effective charges, infrared (IR) absorption, and Raman spectra of MgSiN2 and MgGeN2. From the results, the values of phonon frequencies have the scale comparable with the values reported in the previous theoretical work. Longitudinal optical (LO) and transverse optical (TO) splitting was also included in this work. Some small alteration of phonon frequencies were then found, which is caused by LO-TO splitting at zone-center. In addition, Born effective charge calculation reveals that MgSiN2 and MgGeN2 have the same ionic nature compared with the previously reported ZnSiN2 and ZnGeN2 semiconductor. The phonon frequencies that are IR and Raman active were firstly predicted. This clarification on phonon and phonon-related properties as well as related consequences are expected to help revealing more knowledge about the nature of MgSiN2 and MgGeN2 in enhancing/developing the opto-electronics devices.