First principles study on structure and mechanical properties of Cr2AlC

The first principles method is used to study the intrinsic vacancy of Cr, Al, and C in Cr2AlC materials with formation energies of 1.89, 1.95, and 1.07 eV, respectively. It has been proven in previous research that Al layers could be easily removed from Cr2AlC, and the formation energies of Cr2AlC are, therefore, calculated in this study after removing two layers of Al atoms to form Cr2C. The formation energies of the H, He, and O atoms that replace the Al atoms are also calculated to be −2.83, 90.73, and −47.81 eV, respectively. It shows that under irradiation or a high temperature environment, Cr2AlC is easily oxidized to form Cr2C materials. Furthermore, the density of states of Cr2AlC with an Al layer substituted by H, He, and O atoms, as well as the phonon properties of Cr2AlC and Cr2C, are calculated. The results show that the Cr–C metal bond is dominant in Cr2AlC materials to maintain the stability of the structure. The calculation results of mechanical properties show that the presence of Al atoms enhances the plasticity of Cr2AlC.