title: New insight into the helium-induced damage in MAX phase Ti3AlC2 by first-principles studies.
abstract: In the present work, the behavior of He in the MAX phase Ti3AlC2 material is investigated using first-principle methods. It is found that, according to the predicted formation energies, a single He atom favors residing near the Al plane in Ti3AlC2. The results also show that Al vacancies are better able to trap He atoms than either Ti or C vacancies. The formation energies for the secondary vacancy defects near an Al vacancy or a C vacancy are strongly influenced by He impurity content. According to the present results, the existence of trapped He atoms in primary Al vacancy can promote secondary vacancy formation and the He bubble trapped by Al vacancies has a higher tendency to grow in the Al plane of Ti3AlC2. The diffusion of He in Ti3AlC2 is also investigated. The energy barriers are approximately 2.980 eV and 0.294 eV along the c-axis and in the ab plane, respectively, which means that He atoms exhibit faster migration parallel to the Al plane. Hence, the formation of platelet-like bubbles nucleated from the Al vacancies is favored both energetically and kinetically. Our calculations also show that the conventional spherical bubbles may be originated from He atoms trapped by C vacancies. Taken together, these results are able to explain the observed formation of bubbles in various shapes in recent experiments. This study is expected to provide new insight into the behaviors of MAX phases under irradiation from electronic structure level in order to improve the design of MAX phase based materials.
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Yiguo
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Bai
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Xianhu
authors.initials: X
authors.lastname: Zha
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Laboratory of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China.
authors.forename: Jian
authors.initials: J
authors.lastname: He
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Kan
authors.initials: K
authors.lastname: Luo
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Germann
authors.affiliation: College of Art and Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0312, USA.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Francisco
authors.affiliation: Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, China.
authors.forename: Shiyu
authors.initials: S
authors.lastname: Du
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D001608:Beryllium / Q000737:chemistry*; D004583:Electrons; D006371:Helium / Q000737:chemistry*; D008956:Models, Chemical; D011789:Quantum Theory; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
chemical_list: D006371:Helium; D000535:Aluminum; D014025:Titanium; D001608:Beryllium