Study of New MAX Phase Materials: Sc2AX (A = Bi, Br; X = C, B) via Ab-initio Method

Abstract

The ab-initio calculation has been used to investigate the physical properties of Sc–based ternary MAX phases Sc2AX (A = Bi, Br; X = C, B), wherein Sc2BiB, and Sc2BrB have been predicted for the first time. The optimized lattice constants have been obtained by minimizing the total energy. The formation energies, phonon dispersion curves, and elastic constants (Cij) were calculated to confirm the thermodynamic, dynamical, and mechanical stability. The calculation of the electronic band structure revealed that the Sc2BrB compound exhibits a semiconducting nature, whereas the remaining compounds are metallic. The mechanical behavior has been explored by calculating the elastic constants, elastic moduli, and hardness parameters. In this study, Cauchy pressure, Poisson’s ratio (𝜐), and Pugh’s ratio were calculated to assess the ductility and brittleness. Additionally, the fracture toughness and machinability index were computed to understand the resistance to crack propagation and damage tolerance behavior. This study also encompassed discussions of acoustic behavior and the f-index of the Sc2AX phases. The hardness was evaluated by calculating the Vickers hardness. The Debye temperature (ϴD), Grüneisen parameter, specific heat, thermal expansion coefficient, Helmholtz free energy, internal energy, entropy, lattice thermal conductivity (Kph), minimum thermal conductivity (Kmin), and melting temperature (Tm) were calculated to assess the title compound’s suitability as thermal barrier coating materials. The optical properties were explored to assess their response to incident photons and found their compatibility as coating materials to mitigate solar heating. Finally, the obtained properties were compared with those of Sc2AN (A = Bi, Br) so that our research takes a comprehensive form.