Atomic interactions at the interface between iron or iron fluoride, and sodium by the first-principles calculation.

In order to reproduce the atomic interaction at the interface between iron (Fe) and iron fluoride (FeF2, FeF3) and liquid sodium atoms, we created a cluster model in which Na atoms were placed on the surface of each material. The electronic states of each cluster model were calculated using the DV-Xα method, one of first-principles calculations. Figure (a) shows the strength of the covalent bonding (BO: Bond Order) between the central Fe atom of each cluster models and liquid Na atoms. Figure (b) shows the strength of the covalent bonding between the central F atom of each cluster models and liquid Na atoms. It is shown that the covalent bonding of FeF2 with Na atom is relatively larger than that of Fe with Na atom. In contrast, the covalent bonding of FeF3 with Na atom was not much different from that of Fe with Na atom. Figure (c) shows the amount of the difference in ionicity transferred from Na atoms to the central atom of each cluster model. The correlation was found between the oxidation number of Fe atoms by F atoms and the amount of difference in ionicity. [Display omitted] Atomic interactions at the interface involving iron, iron fluorides (iron (II) fluoride and iron (III) fluoride), and sodium were investigated using first-principles calculations. The wettability with liquid sodium was subsequently examined, focusing on the calculated atomic interactions. From a covalent bonding perspective, iron (II) fluoride exhibited weaker bonds between neighboring atoms in the substrate material than iron (III) fluoride. However, it exhibited relatively strong bonds between the substrate material and sodium atoms. In contrast, iron (III) fluoride had stronger bonds between neighboring atoms in the substrate material, with weaker bonds between the substrate material and sodium atoms. Additionally, in terms of ionic bonding, the contact of the sodium atom with the substrate material increased the charge transfer of the substrate material atom, correlating with the oxidation number of iron. Iron (III) fluoride exhibited the most substantial charge transfer among the substrate materials. The charge transfer from the sodium atom to the atom in contact with it was approximately 2.5 times that of iron. This result underscores the change in electronic states induced by the iron or iron fluoride interface, potentially influencing the wettability between the material surface and liquid sodium. [ABSTRACT FROM AUTHOR]