Theoretical studies of structural, elastic, electronic and lattice dynamic properties of AlxYyB1−x−yN quaternary alloys

• Published in: Physica. B, Condensed matter Vol. 406; no. 13; pp. 2521 - 2527
• Main Authors: Ghebouli, B., Ghebouli, M.A., Fatmi, M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01-07-2011; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Elasticity, elastic constants; Electronic structure; Exact sciences and technology; Lattice dynamics; Lattice matched and mismatched alloys; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Optical properties; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; Pseudo-potential calculations; Pseudo-potential calculations; Electronic structure; Optical properties; Lattice matched and mismatched alloys; Elastic modulus; Aluminium Yttrium Borides nitrides Mixed; Refractive index; Lattice parameters; Phonon dispersion; Phonon mode; Density functional method; Generalized gradient approximation; Chemical composition; Permittivity; Bulk modulus
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2011.03.047

A theoretical study on the structural, elastic, electronic and lattice dynamic properties of AlxYyB1−x−yN quaternary alloys in zinc-blend phase has been carried out with first-principles methods. Information on the lattice parameter, the lattice matching to available substrates and energy band-gaps is a prerequisite for many practical applications. The dependence of the lattice parameter a, bulk modulus B, elastic constants C11, C12 and C44, band-gaps, optical phonon frequencies (ωTO and ωLO), the static and high-frequency dielectric coefficients ε (0) and ε (∞) and the dynamic effective charge Z⁎ were analyzed for y=0, 0.121, 0.241, 0.362 and 0.483. A significant deviation of the bulk modulus from linear concentration dependence was observed. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation. The resistance to changes in bond length and lateral expansion in AlxYyB1−x−yN increase with increasing y concentration. We observe that at y concentration about 0.035 and 0.063, AlxYyB1−x−yN changes from brittle to ductile and Γ–X indirect fundamental gap becomes Γ–Γ direct fundamental gap. There is good agreement between our results and the available experimental data for the binary compound AlN, which is a support for those of the quaternary alloys that we report for the first time.