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Regulating the Entropy of Oxygen Ion Transport Using Phonon Features in the Oxygen Local Environment
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DOI：10.1021/acs.chemmater.6c00037.png)
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Abstract
En 中文
Designing solid-state materials with increased oxygen ion conductivity is essential for technologies such as fuel cells and oxygen separation membranes. In this study, density functional theory simulations of perovskite oxygen ion conductors highlight the role of migration entropy and phonon density of states in regulating pre-exponential factors. We report an extensive data set of migration entropies, where increasing migration entropy and pre-exponential factors are correlated with decreasing phonon band centers at the saddle point relative to equilibrium. Analyzing the atomic contributions to migration entropy reveals that the changes in the phonon density of state of atoms in the local environment of the hopping O* ion significantly contribute to migration entropy. This local environment includes the nearest oxygen ions to O*, with contributions from surrounding ions decaying with distance. Stiffer local environments with higher phonon band centers at equilibrium, tend to soften more during ion hopping causing lower phonon band center at the saddle point relative to equilibrium, and higher migration entropy. Analysis of the Meyer–Neldel rule suggests that coupled trends of vibrational and electronic structures govern the trend of simultaneously increasing migration entropy and energy. This insight opens avenues for material design through the strategic decoupling of migration entropy and energy. These findings provide a theoretical foundation to establish migration entropy as a design variable for next-generation ionic conductors.
Keywords:
Entropy
Genetics
Ions
Oxides
Oxygen
Journal
IF:
7
Papers:
2.8W
Citations:
11.4W