Investigations on Radiation Tolerance of Mn+1AXn Phases: Study of Ti3SiC2, Ti3AlC2, Cr2AlC,Cr2GeC,Ti2AlC,and Ti2AlN

Nanolaminated M_n+1AX_n phases as candidate materials for next generation nuclear reactor applications show great potential in tolerating radiation damage. However, different M_n+1AX_n materials behave very differently when exposed to energetic neutron and ion irradiations. Based on first‐principle calculations, the radiation tolerance of two M₃AX₂ and four M₂AX phases were studied in this work, covering all the M_n+1AX_n phases previously investigated with experiments. We have calculated the formation energies of Frenkel pairs and antisite pairs in these materials. The improved radiation tolerance from Ti₃AlC₂ to Ti₂AlC observed by experiments can be understood in terms of different Al/TiC layer ratio as the A atomic plane in the nanolaminated crystal M_n+1AX_n accommodates radiation‐induced point defects. The formation of M_A–A_M antisite pair in M_n+1AX_n materials would provide an alternative way to accommodate the defects resulted from radiation damage cascades, whereas this ideal substitution channel does not exist for Cr₂GeC due to its pronouncedly higher M_A–A_M antisite pair formation energy. To further elucidate their radiation damage tolerance mechanism, we have made a detailed analysis on their interatomic M–X, M–A, and X–A bonding characters. Criteria based on the bonding analysis are proposed to assess the radiation tolerance of the six M_n+1AX_n materials, which can be further applied to explore other M_n+1AX_n phases with respect to their performances under radiation environment.