Intrinsic defect processes and elastic properties of Ti₃AC₂ (A = Al, Si, Ga, Ge, In, Sn) MAX phases

M_n+1AX_n phases (M = early transition metal; A = group 13-16 element and X = C or N) have a combination of advantageous metallic and ceramic properties, and are being considered for structural applications particularly where high thermal conductivity and operating temperature are the primary drivers: for example in nuclear fuel cladding. Here, we employ density functional theory calculations to investigate the intrinsic defect processes and mechanical behaviour of a range of Ti₃AC₂ phases (A = Al, Si, Ga, Ge, In, Sn). Based on the intrinsic defect reaction, it is calculated that Ti₃SnC₂ is the more radiation-tolerant 312 MAX phase considered herein. In this material, the C Frenkel reaction is the lowest energy intrinsic defect mechanism with 5.50 eV. When considering the elastic properties of the aforementioned MAX phases, Ti₃SiC₂ is the hardest and Ti₃SnC₂ is the softest. All the MAX phases considered here are non-central force solids and brittle in nature. Ti₃SiC₂ is elastically more anisotropic and Ti₃AlC₂ is nearly isotropic.