Point defect formation in M2AlC (M = ZrCr) MAX phases and their tendency to disorder and amorphize

摘要

First principles calculations are performed on Zr2AlC and Cr2AlC MAX phases to compare their ability to accommodate point defects under irradiation. Interatomic bonding is stronger in Cr2AlC than Zr2AlC but contrary to expectation Zr2AlC exhibits higher vacancy and antisite pair formation energies. However, interstitials and Frenkel defects are generally more difficult to form in Cr2AlC. The results are attributed to the mixed covalent/ionic/metallic nature of the bonding. Detailed comparison of all the energies suggests that the preferred defects in Zr2AlC and Cr2AlC are the VAl+Ali Frenkel and CrAl+AlCr antisite respectively. Thus the potential response of the two phases to irradiation is different and taking account of other competing defects it is suggested that Zr2AlC is less susceptible to amorphization.