First-principles studies on behaviors of He impurities in d-MAX phase Zr3Al3C5

ABSTRACT Understanding helium (He) incorporation into materials is essential to estimate the material performance in a nuclear environment for the fabrication of nuclear devices. The effect of helium irradiation on Zr3Al3C5 was studied by using the first-principles method. It is found that the He interstitial atoms tend to situate in the Al-C layers in Zr3Al3C5. The calculation of defect formation energy shows that the defects at the Zr sites are the most difficult to form, while vacancies at the Al and C sites are more ready to form in Zr3Al3C5. The numbers of He atoms that can be trapped by an Al(2) and a C(3) vacancy are seven and three, respectively, which show that Al vacancies have a stronger ability to trap He atom than C vacancies. The migration of He in Zr3Al3C5 is also investigated. The results indicate that He impurity atoms migrate more easily along the c-axis than in the a-b basal plane in the Al-C layer. The diffusion barrier of He atom from the Al-C into the Zr-C layer is determined to be 3.13 eV. The results imply that the Al-C layers tend to be disordered while the Zr-C layers exhibit good tolerance of damage under He irradiation. Additionally, we also studied the stress-strain relationships of Zr3Al3C5 under tensile and shear loading, with the ideal tensile strength and shear strength of Zr3Al3C5 predicted.