Fig. 4. (a) The calculated energy barriers for Mn migration in spinel Mn2O4·(X)0.25n for n = 0 (empty) and n = 2 (X = Na+, Li+, H2O and H3O+). The numbers are migration barriers. (b) The traveling pathway of target Mn (gray sphere) from an Oh site to a Td site in the presence of crystal water. The number denotes a distance. (c) The charge density of the traveling Mn at each intermediate migration position.
