A theoretical insight into hydrogen clustering at defects in Ni. (1st February 2021) - He, Shuang
ABSTRACT: Stability of hydrogen clusters at crystallographic defects in Ni has been recently reported in a number of density functional theory investigations at 0 K. It has been suggested that hydrogen atoms can accumulate at such defects as vacancies and grain boundaries in a form of a cluster containing up to six hydrogen atoms and that the formation of the hydrogen agglomerations can have a significant impact on the hydrogen embrittlement processes in Ni-base alloys. In this work, we employ a combination of density functional theory calculations and embedded atom method simulations to investigate the stability of hydrogen clusters at 0 K as well as finite temperatures. At 0 K, comprehensive calculations for stability of hydrogen clusters have shown that the vacancy of Ni exhibits as a stronger binding than grain boundary for hydrogen atoms, both the vacancies and grain boundaries are able to trap a certain amount of hydrogen atoms respectively. However, at the finite temperatures, our results show that stability of hydrogen clusters at crystallographic defects of Ni is limited to temperatures below 300 K and that their appearance at the ambient temperature and therefore an impact on possible hydrogen embrittlement mechanisms is unlikely.