Midinfrared spectrum of undoped cuprates: d-d transitions studied by ab initio methods
Midinfrared spectrum of undoped cuprates: d-d transitions studied by ab initio methods
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未掺杂铜酸盐的中红外光谱：从头算方法研究 d-d 跃迁
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
R. Broer
中科院分区：
文献类型：
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作者：
C. Graaf;R. Broer
我们提出了 d-d 跃迁的从头计算结果，该跃迁出现在未掺杂的铜酸盐化合物的中红外光谱中。有人认为，La2CuO4 和 Sr2CuO2Cl2 中这些跃迁发生的能量低至 0.4 eV。我们研究了一系列含有铜离子六重、五重或四重配位化合物的铜酸盐中 d-d 跃迁能的差异。此外，我们分析了模型系统 CuO 中 3dx22y 2!3dz2 激发能对面内和顶点铜配体距离之比的依赖性。我们的簇计算不支持将 0.4‐1-eV 频带分配给 d-d 跃迁的声子和磁振子边带。另一方面，我们确认了 CuGeO3 中观察到的 1.7 eV 左右峰值的解释是由 d-d 跃迁产生的。
We present results of ab initio calculations for d-d transitions, which arise in the midinfrared spectrum of undoped cuprate compounds. It has been suggested that these transitions arise at energies as low as 0.4 eV in La2CuO4 and Sr2CuO2Cl2. We study the differences in d-d transition energies in a series of cuprates that contains compounds in which the Cu ions are sixfold, fivefold, or fourfold coordinated. Furthermore, we analyze the dependence of the 3dx22y 2!3dz2 excitation energy on the ratio of the in-plane and apex copper— ligand distances in the model system CuO. Our cluster calculations do not support the assignment of the 0.4‐1-eV band to phonon and magnon sidebands of a d-d transition. On the other hand, we confirm the interpretation of the peak around 1.7 eV observed in CuGeO3 as arising from d-d transitions.