Structural, Dynamical, Thermomechanical, Electronic, Magnetic, and Optical Properties of M₂AC (M = Ta, Sc; A=Al, Cd) MAX Phase Compound Via DFT Approach

MAX phase compounds have numerous applications based on their dynamical, thermomechanical, electronic, magnetic, and optical properties. The performance of these compounds can be optimized by tailoring their composition, structure, and processing methods to enhance their unique properties. In the present work, we explored the structural, dynamical, thermomechanical, electronic, magnetic, and optical properties of M2AC (M = Ta, Sc; A=Al, Cd) (i.e. Sc2AlC, Ta2AlC & Ta2CdC) MAX phase compounds using density functional theory (DFT) method with PBE and PBE+U functionals (U=3eV for p-orbital, U=5eV for d-orbital). From a thorough examination of the structural and dynamical properties of Sc2AlC, Ta2AlC, and Ta2CdC compounds, they are found to be structurally and dynamically stable. We examine the thermal properties of these compounds by estimating their phonon velocities, Debye temperature, and various thermodynamic functions. These compounds have exhibited good thermal properties, indicating their applicability to thermoelectric devices. An examination of the mechanical properties of these compounds, including their elastic constants and modulus of rigidity, revealed their hardness and anisotropic behavior. While Sc2AlC & Ta2CdC exhibit bond stretching and metallic-like bonding, Ta2AlC exhibits bond bending and covalent-like bonding. On the other hand, Sc2AlC & Ta2AlC show brittle nature, whereas Ta2CdC shows ductile nature. Electronic and magnetic properties of Sc2AlC, Ta2AlC, and Ta2CdC compounds are investigated based on their band structure, density of states (DOS), and partial density of states (PDOS) plots, and all of them have shown metallic and non-magnetic properties. Upon examining the dielectric function, refractive index, reflection and absorption coefficients, extinction coefficient, and energy loss function of Sc2AlC, Ta2AlC, and Ta2CdC are found to exhibit strong interaction with light, high shielding properties in the infrared region. Hence, Sc2AlC, Ta2AlC, and Ta2CdC compounds can be used in the fields of thermoelectric, optoelectronic, material shielding, energy storage, and sensing devices.