Spin-polarized DFT calculations of elemental effects on hydrogen atom adsorption on FeCrAl (1 1 0) surface

• The three-fold sites are the stable sites for H adsorption on pure Fe / Cr / Al / FeCrAl (1 1 0) surface. • H cannot be adsorbed on the three-fold sites containing Al atom. • Cr atom(s) in the three-fold sites would decrease the adsorption stability of the H atom. • Al atoms nearby can enhance the interaction between H and Cr-containing three-fold sites by charge transfer. FeCrAl alloys, due to their high-temperature oxidation resistance and excellent mechanical properties, are considered as one of the most promising substitutes of the current Zirconium alloy as cladding in light water reactors. Hydrogen generation is an inevitable phenomenon in nuclear reactors, and hydrogen diffusion and retention in the cladding material would cause the deterioration of the mechanical and oxidation-resistant properties. Understanding hydrogen adsorption is of great importance for studying the whole diffusion mechanism. In this paper, spin-polarized density functional theory (DFT) calculations were conducted to investigate the H atom adsorption on the (1 1 0) surface of pure body-centered cubic structure (BCC) Fe, Cr, Al and FeCrAl. Different initial positions (top and three-fold sites) were calculated to assess how the three elements (Fe, Cr, Al) affect H adsorption. The results show that there are strong elemental effects of Cr and Al on H adsorption. H cannot be adsorbed at the top site of FeCrAl surfaces but it is stably adsorbed at the three-fold sites consisting of the Fe and Cr atoms. However, no H adsorption occurs at the three-fold site containing the Al atoms due to their charge deficiency. According to the charge density difference analyses, Al atoms influence the adsorption of Fe-Fe-Cr and Fe-Cr-Cr sites mainly by influencing the interactions between Cr and H.