Anisotropic Elastic and Lattice Dynamical Properties of Cr2AB MAX Phases Compounds

Abstract

The structural, mechanical and lattice dynamical properties of the MAX Phase borides compounds Cr2AB (A= Al, P, Si) have beeninvestigated using the first principles calculations with the generalized gradient approximation (GGA) based on Density FunctionalTheory (DFT). The obtained negative formation energies of $Cr_2AB$ 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, andPoison’s ratio have been calculated. Ionic character has been found for Cr2AB compounds. Also, $Cr_2AB$ is a brittle material while$Cr_2AB$ and $Cr_2AB$are ductile materials. In addition, the elastic anisotropy has been visualized in detail by plotting the directionaldependence of linear compressibility, Poisson ratio, Young’s and Shear moduli. Furthermore, electronic band structures andcorresponding 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. Thisstudy is the first investigation of the MAX Phase borides compounds $Cr_2AB$ (A= Al, P, Si) and could lead to the future studies.