Ab initio study of irradiation tolerance for different M n1AXn phases: Ti3SiC2 and Ti 3AlC2

Abstract

Layered ternary Mn1AXn (MAX) materials are recently proposed to be promising candidates for future fission and fusion programmes because of their unique properties inherited from both ceramics and metals. However, different Mn1AXn materials demonstrate different behaviors when exposed to energetic neutron or ion irradiations. Based on first-principles calculations, we have investigated the irradiation tolerance of two typical Mn1AXn materials: Ti3SiC 2 and Ti3AlC2 from two aspects. First, we make a detailed analysis on the interatomic bonding characters, which are believed to be responsible for the resistance to radiation-induced amorphization. Second, the formation energies of various intrinsic and antisite defects in these two compounds are calculated in order to elucidate their amorphization mechanism. Our results show that the absence of orbitals overlap of Al-C in Ti 3AlC2 renders it more resistant to amorphization compared to Ti3SiC2. In addition, the antisite defects Al Ti(1) and AlTi(2) in Ti3AlC2 have much lower formation energies compared to SiTi(1) and Si Ti(2) in Ti3SiC2, which implies that the replacement of Ti with Al is easier than Si, thus providing an alternative way to accommodate the defects resulted from irradiation damage cascades. These results indicate that Ti3AlC2 is more irradiation tolerant than Ti3SiC2, in accordance with experimental observations. Our results have profound implications for the choice of appropriate MAX phase with best performance to be used in next reaction reactors. © 2014 AIP Publishing LLC.