First principle calculation of helium in La2Zr2O7: Effects on structural, electronic properties and radiation tolerance

First principle calculations based on density functional theory have been employed to study structural effects of trapping helium in La2Zr2O7 pyrochlore. Lattice swelling and the distortion of unit cell have been found in He-La2Zr2O7 systems. By analyzing the electronic structures and chemical bonding of He-La2Zr2O7 systems, weak repulsive and attractive chemical interactions of helium in La2Zr2O7 pyrochlore have been observed. The formation energies have been calculated to assess the relative stability of various helium interstitial configurations and the results show that the octahedral interstitial site is the most stable structure. The cation antisite defect formation energies and the x positional parameter for 48f-site oxygen are calculated to predict the radiation resistance of He-La2Zr2O7 systems. The results indicate that the presence of low concentration of He interstitials may increase the radiation resistance of La2Zr2O7 pyrochlore.