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 Cr 2 AlC 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 Cr 2 AlC, and the formation energies of Cr 2 AlC are, therefore, calculated in this study after removing two layers of Al atoms to form Cr 2 C. 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, Cr 2 AlC is easily oxidized to form Cr 2 C materials. Furthermore, the density of states of Cr 2 AlC with an Al layer substituted by H, He, and O atoms, as well as the phonon properties of Cr 2 AlC and Cr 2 C, are calculated. The results show that the Cr–C metal bond is dominant in Cr 2 AlC 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 Cr 2 AlC.