LiY(SO${}_4$)${}_2$: A Superionic Material Synthesized by Superionic State Hidden in no-Superionic Literature

A potential superionic material LiY(SO${}_4$)${}_2$ has been excavated from the published literatures because its synthesis method and experiment data implied it exists the superionic state. We use $\mathit{\text{ab}}\mathit{\text{initio}}$ calculation to analyzing the differences between solid state and superionic state. We found the diffusion of Li${}^{+}$ from the lattice site to the interstitial site will change the nearest neighbor numbers of O atom from 4 to 8. In order to reduce energy, the reorientation of SO${}_4^{2-}$ must exist accompany with the diffusion of Li${}^{+}$ so the nearest neighbor number of O will keep about 5 in the superionic state. Our work not only presents an example for discovering materials from literatures based on prior knowledge but also reveals the micromechanism of cation-anion coupled dynamics for superionic state.