New ordered MAX phase Mo_2 TiAlC_2: Elastic and electronic properties from first-principles

First-principles computation on the basis of density functional theory (DFT) is executed with the CASTEP code to explore the structural, elastic, and electronic properties along with Debye temperature and theoretical Vickers' hardness of newly discovered ordered MAX phase carbide Mo₂TiAlC₂. The computed structural parameters are very reasonable compared with the experimental results. The mechanical stability is verified by using the computed elastic constants. The brittleness of the compound is indicated by both the Poisson's and Pugh's ratios. The new MAX phase is capable of resisting the pressure and tension and also has the clear directional bonding between atoms. The compound shows significant elastic anisotropy. The Debye temperature estimated from elastic moduli (B, G) is found to be 413.6 K. The electronic structure indicates that the bonding nature of Mo₂TiAlC₂ is a mixture of covalent and metallic with few ionic characters. The electron charge density map shows a strong directional Mo-C-Mo covalent bonding associated with a relatively weak Ti-C bond. The calculated Fermi surface is due to the low-dispersive Mo 4d-like bands, which makes the compound a conductive one. The hardness of the compound is also evaluated and a high value of 9.01 GPa is an indication of its strong covalent bonding.