عنوان مقاله [English]
In this paper, the electronic, phononic and mechanical properties of zinc-blende and wurtzite phases of GaN compound are studied by Density Functional Theory (DFT), generalized gradient approximation (GGA) and pseudo potentials. Results show both phases are semiconductors. The calculated band gaps are 2 and 2.2 eV for zinc-blende and wurtzite phases correspondingly. Bulk modules are obtained by fitting the variation of energy vs. the lattice constants data to the murnaghan equation of state. The phonon dispersion curves are obtained in high symmetry directions. The elastic constants are calculated by the slope of the phonon acoustic modes in different directions. These constants are =272, =122 and =127 GPa in zinc-blende phase and =301, =380, =85, =88, =125, =153 GPa in wurtzite phase. Our results are compared with other calculation and are in good agreement with them. Young modules are calculated in tensile and comparison modes for wurtzite phase and compared with zinc-blende phase .The results show; the wurtzite phase is harder in z direction.