A first-principles calculation was used to investigate the effects of He in an Fe Σ5(310)/[001] grain boundary using the SIESTA code, for which the reliability of the pseudopotential and the basis set were systematically tested. The formation and segregation energies were calculated for various substitutional and interstitial cases in order to determine the site preference and the segregation properties of He in the Fe GB. It was demonstrated that the He segregation either broke (substitution) or weakened (interstitial) the surrounding interfacial Fe–Fe bonds, leading to the grain-boundary tensile strength reduction.

First-Principles Study of He Effects in a BCC Fe Grain Boundary: Site Preference, Segregation and Theoretical Tensile Strength. L.Zhang, X.Shu, S.Jin, Y.Zhang, G.H.Lu: Journal of Physics - Condensed Matter, 2010, 22[37], 375401