A comprehensive investigation of structural, mechanical and optoelectronics attributes of M2AsC (M = Zr, Hf, Ta, W) MAX phase carbides: A DFT investigation

Abstract

This research utilizes first-principles calculations to systematically investigate the phase stability, mechanical properties, and optoelectronic characteristics of the M₂AsC (M = Zr, Hf, Ta, and W) MAX phase carbides. The phase stability of these M₂AsC compounds is evaluated through the computation of formation enthalpies, which demonstrates that all analyzed compounds exhibit both structural and thermodynamic stability. To evaluate mechanical stability, we calculated the elastic stiffness constants, confirming the mechanical robustness of the studied MAX phases. Furthermore, the calculated Pugh and Poisson ratios reveal a brittle nature for Hf₂AsC and Ta₂AsC materials, while Zr₂AsC and W₂AsC compounds display notably high B/G ratios, indicating superior hardness relative to the other compounds studied. The band structure and density of states analyses confirm a metallic character for all M₂AsC compounds. A prominent hybridization effect is identified between the d-orbitals of M and the p-orbitals of C, while the interaction between the p-orbitals of M and As is comparatively less significant. The presence of pseudogaps near the Fermi level is linked to the orbital hybridization involving M, As, and C atoms. Charge density difference maps further elucidate the strong covalent bonding between M and C atoms, contrasted by a relatively weaker bonding interaction with As atoms. Additionally, a comprehensive examination of optical properties reveals that the highest absorptivity occurs within the energy range of 7.5–20 eV. The optical spectra of the MAX phases span from 1.7 eV in the infrared region to 11 eV in the ultraviolet region, indicating their potential as effective energy absorbers in the UV spectrum. Overall, the distinctive properties exhibited by M₂AsC compounds suggest their viability for a broad spectrum of applications across diverse fields.