Ab Initio Study of the Energetics, Electronic Properties, and Chlorine Migration Behavior of B2-FeAl (110) Surface by Microalloying

Ab initio methods based on DFT are utilized to study the formation energy, adsorption energy, and electronic properties of pure and X-doped (X = Mo, Ti, Ni) B2-FeAl (110) surface configurations. The effect of microalloying element doping on the corrosion resistance of B2-FeAl coating to molten chlorinated salts was evaluated by the CI-NEB method. Our results show that the Ni atom preferentially occupies the position of the Fe atom, while the Mo and Ti atoms preferentially replace the Al atom in the supercell. The Cl atom tends to be adsorbed at the SB-FeAl site on a pure B2-FeAl (110) surface. The adsorption energies of a single chlorine atom at stable adsorption sites of Ni-doped B2-FeAl (110) surface are small, which means that Ni doping reduces the possibility of corrosion. The PDOS diagrams confirm that for the chlorine adsorption model of Mo-doped B2-FeAl (110) surface, strong hybridization between Mo-d, Al-p, and Fe-d orbitals occur in the energy region of −4.5~−2 eV and 0.5~2.5 eV, while in the energy range of −7.0~4.8 eV, Cl-p interacts with Mo-d and Al-s, respectively, indicating that Cl bonds with Mo and Al atom, respectively. The addition of Mo and Ni hinders the diffusion of chlorine atoms on the surface, weakens the corrosion rate of B2-FeAl in chlorinated molten salt, and improves the corrosion resistance of B2-FeAl coating. However, Ti doping promotes the migration of chlorine atoms and increases the corrosion rate of B2-FeAl in chlorinated molten salt to a certain extent. The aim of this study is to reveal the corrosion resistance mechanism of FeAl coating from the atomic level and provide a theoretical basis for the application of chloride molten salt as an efficient heat storage medium in the field of photothermal.