Exploring the electronic, mechanical, anisotropic and optical properties of the Sc-Al-C MAX phases from a first principles calculations

MAX phase series materials have the excellent thermal, electrical and mechanical properties and have great research potential. To achieve a comprehensive understanding of the utilization of Sc-Al-C MAX phases, the mechanical properties, electronic structures, elastic anisotropy and optical properties of these compounds were calculated by first-principles calculations. The lattice parameters and equilibrium volumes agree with the existing experimental data. The elastic constants show that these compounds are mechanically stable. In addition, the enthalpy of formation indicates that they are thermodynamically stable. The metallic properties of the phases are verified by the analysis of their density of states and band structures. ScAl3C3 has the largest shear and Young's modulus because of its strong chemical bonding and the values are 150.91 GPa and 346.65 GPa, respectively. Sc2AlC shows the lowest degree of anisotropy due to the lack of strong direction in the bonding. The G/B ratio and nu values support that all these compounds are brittle materials. By calculating the absorption coefficient, it is shown that these compounds can be used as optoelectronic devices in the ultraviolet range. The reflectance images show that these compounds can be used as thermal insulation coatings.