Ab- initio Calculations of the Physical Properties in Gallium Nitride at Equilibrium Phases: Rocksalt and Wurtzite

Authors : Cengiz SOYKAN

Pages : 13-23

Doi:10.19113/sdufbed.38099

View : 23 | Download : 10

Publication Date : 2018-04-16

Article Type : Research Paper

Abstract :Ab-initio total energy calculations have been performed utilizing the Density Functional Theory insert ignore into journalissuearticles values(DFT); inside the generalized gradient approximation insert ignore into journalissuearticles values(GGA); parameterized by Perdew-Burke-Ernzerhof insert ignore into journalissuearticles values(PBE);. Interactions of the ions and electrons with each other’s was characterized via PAW potential within the valance electron configurations Ga-4s 2 4p 1 and N-2p 2 2p 3 to investigate the physical properties in the rocksalt B1 and wurtzite B4 phases. The equilibrium transition pressure insert ignore into journalissuearticles values(P t ); from B4 to B1 was estimated at about 33.66 GPa by using the common tangent construction. The DFT calculations indicate that the upper bands of wurtzite B4 between -0.256 eV and the Fermi level were mostly owing to N-p states. The lowest conduction bands were consisted of a mixture of N-s and Ga-s states. The valance band maximum and the conduction band minimum occured at the Γ symmetry point. Concordantly, B4 phase of GaN had a direct band gap at Γ-point, which calculated as 1.702 eV. The highest valance band of rocksalt B1 were consisted of with a major contribution of N-2p states. Although, the indirect band gap of the rocksalt B1 phase has been reported from the valance band maximum at the L-point to the conduction band minimum along the X direction [7], we observed the indirect energy band gap from the valance band maximum at the L-point to the conduction band minimum along the Γ direction. Our calculated value of indirect energy band gap for the rocksalt B1 phase was 0.777 eV and it was lower than the previous calculations.
Keywords : Density functional theory, Ab initio calculations, Elastic stiffness coefficients, Phase transition pressure, Mechanical properties, Electronic structure