Investigations on Radiation Tolerance of M n +1 AX n Phases: Study of Ti 3 SiC 2 , Ti 3 AlC 2 , Cr 2 AlC, Cr 2 GeC, Ti 2 AlC, and Ti 2 AlN

Nanolaminated M n +1 AX n phases as candidate materials for next generation nuclear reactor applications show great potential in tolerating radiation damage. However, different M n +1 AX n materials behave very differently when exposed to energetic neutron and ion irradiations. Based on first‐principle calculations, the radiation tolerance of two M 3 AX 2 and four M 2 AX phases were studied in this work, covering all the M n +1 AX 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 Ti 3 AlC 2 to Ti 2 AlC 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 +1 AX n accommodates radiation‐induced point defects. The formation of M A –A M antisite pair in M n +1 AX 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 Cr 2 GeC 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 +1 AX n materials, which can be further applied to explore other M n +1 AX n phases with respect to their performances under radiation environment.