Exploring the structural, dynamical, mechanical, electronic, magnetic, and optical properties of Ta2AlN, Ti2AlN & Ti2GaN MAX phase compounds: First-principles study

MAX phase compounds are emerging nanolaminate materials possessing both ceramic and metallic properties rendering their applicability in a wide range of devices. In this study, we investigated the structural, mechanical, dynamical, electronic, magnetic, and optical properties of Ta2AlN, Ti2AlN and Ti2GaN MAX phases materials applying density functional theory (DFT). The computational results show that these compounds are structurally stable. The phonon dispersion curve of Ta2AlN, Ti2AlN and Ti2GaN shows that they are dynamically stable. The computed values of elastic constants and moduli of rigidity pertaining to these compounds suggest that these compounds are mechanically stable, and that they have anisotropic, hardness, and bond stretching nature. Based on the computed values of Pugh's ratio and Poisson ratio, Ta2AlN exhibits ductile nature while Ti2AlN and Ti2GaN exhibit brittle nature. Electronic properties of the materials are investigated through their band structure and density of states (DOS) calculations and the outcome suggests that these compounds exhibit metallic properties. Further investigation of the magnetic properties based on density of states (DOS) and partial density of states (PDOS) plots, indicate that Ta2AlN and Ti2GaN exhibit non-magnetic for GGA: PBE and GGA: PBE + U functional, while Ti2AlN exhibit non-magnetic properties for GGA: PBE functional, and exhibits magnetic properties for GGA: PBE + U functional. The dielectric function, reflection coefficient, absorption coefficient, refractive index, energy loss function, and extinction coefficient plots of GGA: PBE and GGA: PBE + U functional were used to explore the optical properties of Ta2AlN, Ti2AlN and Ti2GaN materials. Refractive index and extinction coefficient plots demonstrate that the opacity of these materials increases at low photon energy range. The dielectric function plot shows that the materials respond to lower photon energies (below 1 eV). Additionally, the absorption and reflection coefficients have high values in almost all the photon energies, implying that these materials are suitable for radiation shielding applications. Further, analysis of the energy loss function indicates that the maximum energy loss occurs in the UV region. Therefore, from the computational results of the MAX phase compounds investigated in this study it is inferred that these compounds have wide range of applicability including, radiation shielding, photonics, optoelectronics, electronics, UV-absorbing coatings, and high ductility and brittleness.