Comparative study on the radiation resistance of pure and He-doped Gd2Zr2O7 pyrochlore by DFT + U calculation

Abstract

The helium accumulation in the pyrochlore ascribed to alpha decay has important effects on its performance during service. This work adopts first-principle method to investigate the structural evolution, discrepancy in mechanical properties and radiation resistance before and after He doping in Gd2Zr2O7 pyrochlore. By calculating each configuration of pure and He-doped Gd2Zr2O7, it is found that the unit cell expands and distorts due to the doping helium. Single helium atom prefers to occupy the octahedral interstitial site and Gd vacancy. The variation of elastic constants and elastic modulus implies that helium doping has no obvious damage to mechanical stability. He-Gd2Zr2O7 systems have lower antisite defects formation energy and higher vacancy defects formation energy, indicating better radiation resistance. Moreover, the electronic structure analysis shows that <Zr-O> bonds have a greater influence on radiation resistance than <Gd-O> bonds. This study demonstrates that Gd2Zr2O7 pyrochlore would exhibit excellent radiation resistance in long-term service.