| Abstract
| - Migration of Li+ ions via the vacancy mechanism in LiX (X = F, Cl, Br, and I) with the rocksalt andhypothetical zinc blende structures and Li2X (X = O, S, Se, and Te) with the antifluorite structure has beeninvestigated using first-principles projector augmented wave calculations with the generalized gradientapproximation. The migration paths and energies, determined by the nudged-elastic-band method, are discussedon the basis of two idealized models: the rigid-sphere and charged-sphere models. The trajectories and energyprofiles of the migration in these lithium compounds vary between these two models, depending on the anionspecies and crystal structure. The migration energies in LiX with both the rocksalt and hypothetical zincblende structures show a tendency to decrease with increasing periodic number of the anion species in theperiodic table. This is consistent with the widely accepted view that anion species with large ionic radii andhigh polarizabilities are favorable for good ionic conduction. In contrast, Li2O exhibits the lowest migrationenergy among Li2X compounds, although O is the smallest among the chalcogens, indicating that electrostaticattractive interactions play the dominant role in the inter-ion interactions in Li2O and, therefore, in the ionmigration.
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