Collective diffusion within the superionic regime of Bi2O3

Article

关键词: INITIO MOLECULAR-DYNAMICS;    LINKING STRUCTURE;    ION DIFFUSION;    CONDUCTOR;    THERMODYNAMICS;    TRANSPORT;   

DOI  :  10.1103/PhysRevB.101.104309

来源: SCIE

【 摘 要 】

The delta phase of Bi2O3 has the highest known value of oxide ion conductivity within the solid state and, therefore, remains a benchmark for the development of future generations of electrolyte materials to fuelcell technologies. Conventionally, the high value of conductivity in delta-Bi2O3 has been explained by a large concentration of inherent vacancies together with a strongly polarizable Bi-O bond. We show from ab initio molecular dynamics simulations that short chains of collective migrating oxygens also contribute strongly to the high value of conductivity with the single-particle Nernst-Einstein (N.E.) conductivity to collective (dc) conductivity sigma(N.E.)/sigma(dc) similar to 0.57 +/- 0.05 at 1033 K. The nature of collective events is investigated from a hopping model, the distinct part of the van Hove function and from the extent of dynamical heterogeneities in the superionc regime. Results from this analysis indicate that the main contribution to collective ionic diffusion in delta-Bi2O3 involves short collinear chains of two or three oxygens. These chains are either initiated by an oxygen that jumps into an already occupied oxygen cavity (where they coexist for a very short time before the residential oxygen is kicked out of its cavity) or from a jump into a vacant cavity which triggers a next-nearest-neighboring oxygen to migrate. Since delta-Bi2O3 is easily stabilized in a range of environments, the nature of these collective chains can give important insight into the design of delta-Bi2O3-based fuel cells for the future.

【 授权许可】

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