Effect of Nb precipitate on defect formation and migration energies in bi-crystalline Zr

In this article, molecular statics based simulations were performed to study the effect of Nb precipitate on the defect formation and migration energies in the bi-crystals of zirconium and niobium alloy (Zr-Nb). In order to resemble the experimentally observed configurations of grain boundaries in Zr, symmetrical and asymmetrical tilt grain boundaries were generated along [0001] as tilt axis. It has already been established that point defect formation energies are lower in the vicinity of grain boundaries, as compared to bulk values, but literature is almost mute on the effect of Nb precipitate on these energies. A comparison between these energies in Zr-Nb alloy containing (0%, 1%, 2.5% and 5%) Nb is reported in this work. Vacancy migration energy was estimated with the help of nudged elastic band algorithm. Simulations performed in this article lead to a conclusion that addition of Nb in the Zr-Nb alloy significantly effects the formation as well as migration energies of the defects. It can be concluded that an appropriate weight percentage of Nb helps in enhancing the defect sinking capabilities of grain boundaries in bi-crystalline Zr.