We examined the electronic property of Sb-doped Na_0.785CoO₂ using density functional calculations based on GGA+U formalism. We demonstrated that Sb dopants were the most stable when replacing Co ions within the complex Na_0.875CoO₂ lattice structure. We also showed that the Sb_Co dopants adopted the + 5 oxidation state introducing two electrons into the host Na_0.875CoO₂ compound. The newly introduced electrons recombined with holes that were borne on Co⁴⁺ sites that had been created by sodium vacancies. The elimination of Co⁴⁺ species, in turn, rendered Na_0.875(Co_0.9375Sb_0.0625)O₂ non-magnetic and diminished the compound’s thermoelectric effect. Furthermore, the Sb_Co dopants tended to aggregate with the Na vacancies keeping a minimum distance. The conclusions drawn here can be generalised to other highly oxidised dopants in Na_xCoO₂ that replace a Co.

中文翻译：

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Sb Co掺杂剂诱导的Na 0.875 CoO 2的磁性和塞贝克效应的抑制

我们使用基于GGA + U形式论的密度泛函计算方法研究了掺Sb的Na _0.785 CoO ₂的电子性质。我们证明当在复杂的Na _0.875 CoO ₂晶格结构中替换Co离子时，Sb掺杂剂最稳定。我们还表明，Sb _Co掺杂剂采用+ 5氧化态，将两个电子引入主体Na _0.875 CoO ₂化合物。新引入的电子与由钠空位产生的Co ⁴⁺位点上携带的空穴重组。消除了Co ⁴⁺物种后，Na _0.875（Co _0.9375 Sb _0.0625）O ₂无磁性，并降低了化合物的热电效应。此外，Sb _Co掺杂物趋于聚集，而Na空位保持最小距离。此处得出的结论可以推广到Na _x CoO ₂中的其他高度氧化的掺杂剂，以代替Co。