Ab-initio Assessment of the Electronic, Mechanical, Thermal, Optical and Phonon Properties of B3-AlAs

The applications of group III–V minerals are closely linked to their structural and compositional polymorphs and have drawn great attention due to their vast electronic and optoelectronic technology. Aluminum arsenide (AlAs) is a group III–V coordinated tetrahedral crystal material. The present investigation addresses the aspects of optical extinction coefficient, energy loss function, refractive index, and reflectivity of the B3-phase AlAs which are still missing in reported studies. Optical properties can be used to show materials application to birefringent. This work aims at giving a deep understanding of B3-phase AlAs minerals, in terms of electronic structure, bond strength, mechanical properties, dynamical and optical properties. In this paper, ab-initio assessment of the above properties is carried out using the methods of density functional theory (DFT) as implemented in quantum espresso and thermo_pw codes. The material simulations are performed self-consistently by using pseudopotentials in the form of generalized gradient approximation (GGA) and local density approximation (LDA) respectively, to account for the exchange correlations. The energy and charge density convergence tests were examined to study the ground-state properties. The band structure and density of state (DOS) diagrams plotted demonstrate an indirect semiconducting state with an energy band gap of 1.45 eV (GGA) and 1.34 eV (LDA), as well as Al-As bond length, all in satisfactory accord with data from experiment and theory. Mechanically, analysis of the 3D-projections demonstrates that B3-AlAs possesses a high degree of anisotropy, which is further confirmed by the calculated Zener- and universal-anisotropic indexes. The evaluated Debye temperature θ(D) = 397.724 K reflects the feasibility of the material being brittle, while the Debye heat capacity reveals the Dulong-Petit limit. The Debye frequency and Grüneisen’s parameter (γ) calculated are depicted for the first time. The general profiles of the optically dependent dielectric functions of B3-AlAs under ambient conditions are discussed. Analysis of the obtained optical parameters, such as the reflectivity, refractive index, extinction coefficient, and energy loss function suggests the material is a good dielectric due to the appearance of the spectrum mostly in the ultra-violet region.