First-principles study of the elasticity, piezoelectricity, and vibrational modes in LiGaO₂ compared with ZnO and GaN

The lattice-dynamical properties of LiGaO₂ have been studied by means of first-principles density-functional calculations using the pseudopotential linear-response approach in the local-density approximation. For comparison, similar calculations are performed for the related materials ZnO and GaN. The quantities calculated are the elastic constants, the piezoelectric constants, the static and high-frequency dielectric constants, and the zone-center vibrational modes. The latter are used to calculate infrared optical spectra and compared with experiment. The results are compared to available experimental data, indicating overall satisfactory agreement typical of the methodology used. The nature of the vibrational modes is examined in terms of the mode eigenvectors and indicates a large mixing of wurtzite derived modes due to the lower symmetry.