First Principle Investigation by Hybrid Functional Method on the Physical Properties of Narrow Band Gap ScxY1–xN (0 ≤ x ≤ 1) Solid Solutions

The structural, electronic, optical and elastic properties of Sc_xY_1–xN (0 ≤ x ≤ 1) alloys in rocksalt phase have been investigated using first-principles method based on density functional theory (DFT). The lattice constants decrease while the bulk modulus increases with Sc concentration increasing. Result shows that with the increase of Sc constituent, the band gap of Sc_xY_1–xN increases and the band structure for x = 0.25, 0.50 and 0.75 are direct gap semiconductors. The density of states and optical constants such as complex dielectric function, extinction coefficient, refractive index and absorption coefficient are also calculated and analyzed in detail. The sound velocities and the Debye temperatures are calculated for all the Sc_xY_1–xN alloys using the calculated elastic constants and elastic modulus. The effect of Sc composition on elastic constants C_ij, elastic modulus (bulk modulus B, shear modulus G, Young’s modulus E), Poisson’s ratio (ν) and B/G are investigated for all the Sc_xY_1–xN alloys. The longitudinal and shear wave velocities (v_s, v_l) and Debye temperature θ_D are calculated for all the Sc_xY_1–xN alloys using the calculated elastic constants and elastic modulus. Further, elastic wave velocity (v_s, v_l) and Debye temperature all monotonically decrease with increasing Sc concentration. The agreement between the present results and the known data that are available only for ScN and YN is generally satisfactory. In addition, our results for the narrow band gap of Sc_xY_1–xN alloys (0 < x < 1) are predictions.