Theoretical investigations on helium trapping in the Zr/Ti₂AlC interface

MAX phases have been suggested to be applicable in the next generation nuclear reactors for their advantages in thermal/mechanical properties at high temperatures and radiation damage resistance. In the present investigations, the stabilities and formation energies of helium defects in the Zr/Ti₂AlC interface are studied by first principles calculations. The calculations are performed using four possible interface models, and the trap of helium atoms in interstitial or vacancy sites are taken into consideration. According to the predicted formation energies, a single He atom tends to reside between the Al and Ti planes. The results also imply that Al vacancies are better able to trap He atoms. The stepwise rise for the trapping energies with the increasing number of trapped He atoms are determined in an Al vacancy and the corresponding swelling effect is examined. These investigations may provide new insight into the underlying mechanisms of helium bubble nucleation and formation in the Zr/Ti₂AlC interface.