First-principles investigation into the effect of Cr on the segregation of multi-H at the Fe Σ3 (1 1 1) grain boundary

First-principles calculations were carried out to investigate the effect of Cr on segregation of multiple H atoms in the Σ3 (1 1 1) grain boundary in bcc Fe. In the absence of Cr, four H atoms can be trapped at the interstitial site of the Fe grain boundary (areal density: 28 nm−2), and no H2 molecules are formed. The presence of Cr, however, suppresses the segregation tendency of H and only two H atoms can be trapped at this grain boundary. Although the volume expansion associated with the segregation of Cr to the grain boundary promotes H segregation, such a booting effect is unable to remedy the repulsion of H resulted from charge density increase in the grain boundary core. As a consequence, Cr mitigates H aggregation at the Σ3 (1 1 1) grain boundary in bcc Fe.