The influence of temperature and pressure on the electronic, optical and elastic properties of GaN in Wurtzite phase

In this theoretical study, we show the effect of pressure and temperature on the structural (lattice constants, the bulk modulus B0 and its first derivative B0), electronic (Band structures and Partial density of states (PDOS)), optical (static dielectric constant and the static refraction index), and elastic properties (the elastic constants (C11, C12, C33, and C44), bulk modulus (B), shear modulus (G), and Young's modulus (E)) using pseudo-potential plane-waves (PP-PW) approach as implemented in the CASTEP code based on the density functional theory (DFT) and generated gradient approximation (GGA) in the scheme of Perdew–Burke–Ernzerhof (PBE). Our data show the transition phase of Gallium Nitride (GaN) from wurtzite (B4) to rocksalt (B1) at P = 45.08 GPa. As for the electronic properties, we found that the band gap decreases with the increase of temperature. Whatever the temperature and pressure value are, we noticed that Gallium Nitride has a direct band gap. From the elastic properties, we can say that the compound is mechanically stable at any value of temperature and pressure. Though results are very close to the experimental data and other theoretical results at P = 0 GPa and T = 0 K, there are unfortunately no experimental results and theoretical data to compare with the present results at higher temperatures and under different pressures. We hope our results might serve as a reference for future studies.