Comparative study of predicted MAX phase Hf₂AlN with recently synthesized Hf₂AlC: a first principle calculations

The physical properties including thermodynamic and optical properties, electronic charge density, Fermi surface, Mulliken bond overlap population and Vickers hardness of newly synthesized MAX phase Hf₂AlC and predicted Hf₂AlN phase have been explored using density functional theory for the first time. We revisit lattice and elastic constants, band structure and density of states to weigh the reliability of our calculations. The mechanical and dynamical stabilities of these compounds have been ensured. The brittle nature of Hf₂AlX (X=C and N) compounds is also confirmed by the Pugh (G/B>0.57) and Poisson ratio (<0.26). The electronic band structure and density of states show the metallic conductivity with foremost contribution of Hf-5d states at the Fermi level. The mixture of covalent, metallic and ionic bonding is ensured by Mulliken population and charge density mapping. Low Vicker hardness value indicates soft material and easily mechinable nature of the phases. The reflectivity curves show the maximum values of 93% at 10.3 eV and 99% at 13.7 eV for the compounds Hf₂AlC and Hf₂AlN, respectively, that endorse the capability of reducing solar heating of these compounds. Excellent correlations are also found in all physical properties of these compounds. (author)