Anisotropic Elastic and Lattice Dynamical Properties of Cr2AB MAX Phases Compounds

The structural, mechanical and lattice dynamical properties of the MAX Phase borides compounds Cr2AB (A= Al, P, Si) have been investigated using the first principles calculations with the generalized gradient approximation (GGA) based on Density Functional Theory (DFT). The obtained negative formation energies of Cr2AB indicate that these compounds are stable and could be synthesized. Some basic physical parameters such as lattice constants, elastic constants, bulk modulus, Shear modulus, Young’s modulus, and Poison’s ratio have been calculated. Ionic character has been found for Cr2AB compounds. Also, Cr2AlB is a brittle material while Cr2SiB and Cr2PB are ductile materials. In addition, the elastic anisotropy has been visualized in detail by plotting the directional dependence of linear compressibility, Poisson ratio, Young’s and Shear moduli. Furthermore, electronic band structures and corresponding partial density of stated have been examined and it has been found that these compounds have metallic character. Moreover, the phonon dispersion curves as well as corresponding phonon partial density of states (PDOS) have been obtained. This study is the first investigation of the MAX Phase borides compounds Cr2AB (A= Al, P, Si) and could lead to the future studies