Behaviors of helium in Cr2AlC from first principles

Abstract

AbstractThe properties of helium incorporation and transport in Cr2AlC have been investigated using first principles method. The results of calculation show that a single helium atom is preferred to reside at an interstitial position near the Al plane in perfect Cr2AlC crystal, attributing to the low predicted formation energy. Helium atoms are expected to aggregate in Al layers. The interaction between helium and lattice atoms is primarily elastic due to the closed‐shell electronic structure of helium. The Doping of helium leads to a weakening of the Cr–Al bonds. Furthermore, an interstitial helium atom is likely to migrate along an indirect migration pathway from the hexahedral interstitial position on Al plane (IAlC), passing by the nearest tetrahedral interstitial position near Al plane (IAlCr), and finally reach to another hexahedral interstitial position (IAlC) with an activation energy of 1.21 eV. The high activation energy suggests a relatively low migration for helium atoms in Cr2AlC as well as a slow growth rate of helium bubbles for the early stage of helium irradiation.