The effect of Ti doping on He migration behavior in β-TMH₂ (TM = Sc and Er): first-principles calculations

In this work, the stability and migration behavior of He in Ti doped β-TMH₂ (TM = Sc and Er) are investigated by using density functional theory (DFT) calculations. The addition of Ti atoms reduces the formation energy of He in TMH₂ (TM = Sc and Er). Ti atoms repel He atoms in TMH₂ (TM = Sc and Er), reducing the stability of He in the interstitial sites. In addition, the effects of different Ti doping concentrations on He in TMH₂ (TM = Sc and Er) were explored. The results of the total density of states confirmed that the stability of He atoms decreases with the increase of Ti atom concentrations. The binding energy between He atoms in Ti doped TMH₂ (TM = Sc and Er) also decreases as the concentration of Ti atoms increases. The migration barrier of He in the tetrahedral vacancies reaches a maximum of 0.71 eV with a Ti doping concentration of 2.0% in ScH₂. The two He atoms have a weak repulsive force, and it is difficult for the He atom to approach the vacancy near the Ti atom. The study could provide an effective measure for TMH₂ (TM = Sc and Er) to realize good He fixating capability.