A first-principles study of helium storage in oxides and at oxide–iron interfaces

Abstract

Density-functional theory calculations based on conventional as well as hybrid exchange-correlation functionals have been carried out to study the properties of helium in various oxides (Al 2 O 3 , TiO 2 , Y 2 O 3 , YAP, YAG, YAM, MgO, CaO, BaO, SrO) as well as at oxide-iron interfaces. Helium interstitials in bulk oxides are shown to be energetically more favorable than substitutional helium, yet helium binds to existing vacancies. The solubility of He in oxides is systematically higher than in iron and scales with the free volume at the interstitial site nearly independently of the chemical composition of the oxide. In most oxides He migration is significantly slower and He-He binding is much weaker than in iron. To quantify the solubility of helium at oxide-iron interfaces two prototypical systems are considered (Fe|MgO, Fe|FeO|MgO). In both cases the He solubility is markedly enhanced in the interface compared to either of the bulk phases. The results of the calculations allow to construct a schematic energy landscape for He interstitials in iron. The implications of these results are discussed in the context of helium sequestration in oxide dispersion strengthened steels, including the effects of interfaces and lattice strain.

Effects of Cr and W additions on the stability and migration of He in bcc Fe: A first-principles study

“…In terms to the above formation energies, the binding energy between two defects A and B is defined by [30,31]:…”

Defect Distributions and Transport in Nanocomposites: A Theoretical Perspective

“…Further, it has been proposed that the behavior of He in oxide dispersion strengthened steels is dictated by a similar energy landscape, albeit one that also involves a trap state at the interface. [28] Thus, He implantation experiments might provide another avenue for validating the premises of the model presented here.…”

Stable Storage of Helium in Nanoscale Platelets at Semicoherent Interfaces

“…MDIs are an intrinsic part of semi-coherent interfaces [17,18]. Experiments have shown that, on average, ~25 He atoms may be stored at each MDI without forming a bubble [19]-far in excess of the number expected from solubility arguments [20].…”