Migration paths of the Na+-ion diffusion for minerals of the lovozerite group: crystallochemical and DFT modeling

Abstract

For 11 minerals of the lovozerite group, theoretical investigations of Na⁺-ion migration were performed. The combination of GT, BVSE, and DFT-NEB approaches allows for studying the relationship between the crystallochemical energetic characteristics and ion-conductive properties of solid electrolytes. The constructed tilings made it possible to establish common types of cavities (tiles) for these structures. The location of sodium in large cavities suggests that these cavities can serve as new building blocks for modeling zeolite-like frameworks. GT analysis indicated that combeite, townendite, kapustinite and kazakovite have the widest Na⁺-migration paths among the 11 minerals. Using the BVSE approach, values of the migration barriers were obtained. For combeite, townendite, kapustinite and zolotarevite, the values of the migration barriers are in the range of 0.60–0.80 eV. DFT-NEB modeling results are in good agreement with the results from BVSE and GT analyses. It was found that minerals of this group have structures that are promising for the creation of new cation-conducting materials.