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arXiv 1106.2893cond-mat.str-el
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从头算局域相互作用研究$\rm Ca_3Co_4O_9$化合物的电子结构

Electronic structure of the $\rm Ca_3Co_4O_9$ compound from ab initio local interactions

Julien Soret, Marie-Bernadette Lepetit

摘要:

我们用完全关联从头计算方法确定了热电失配化合物$\rm Ca_3Co_4O_9$的Hubbard和t-J模型的有效参数。至于$\rm Na_xCoO_2$族,费米能级轨道是钴原子的$a_{1g}$轨道; $e'_g$的能量总是低于240毫电子伏以上。发现电子相关性非常大的$U/t\sim 26$以及作为结构调制的函数的参数波动。主要的后果是部分$a_{1g}$电子本地化和波动的平面内从AFM到FM的磁交换。根据从头算结果和496 K相变讨论了Seebeck系数随温度的变化.

英文摘要:

We used fully correlated ab initio calculations to determine the effective parameters of Hubbard and t - J models for the thermoelectric misfit compound $\rm Ca_3Co_4O_9$. As for the $\rm Na_xCoO_2$ family the Fermi level orbitals are the $a_{1g}$ orbitals of the cobalt atoms ; the $e'_g$ being always lower in energy by more than 240\,meV. The electron correlation is found very large $U/t\sim 26$ as well as the parameters fluctuations as a function of the structural modulation. The main consequences are a partial $a_{1g}$ electrons localization and a fluctuation of the in-plane magnetic exchange from AFM to FM. The behavior of the Seebeck coefficient as a function of temperature is discussed in view of the ab initio results, as well as the 496\,K phase transition.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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