Conductivity and ' negative U ' for ionic grain boundaries
نویسنده
چکیده
We show that charge-transfer excitations (like 2M2-+ M+ M3-) can be lowered greatly in energy near grain boundaries. where sites are no longer equivalent. In special cases the excitations may be exothermic ('negative-Lr behaviour); likely cases include (320) and (122) grain boundaries in FeO. Consequences include effects on conductivity, segregation of impurities with different valence, and on other charge-state-dependent properties.
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