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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Local structure and excitations in systems with CuF64- units: lack of Jahn-Teller effect in the low symmetry compound Na2CuF4
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Local structure and excitations in systems with CuF64- units: lack of Jahn-Teller effect in the low symmetry compound Na2CuF4

机译：具有CUF64-单位的系统中的局部结构和激发：低对称化合物NA2CUF4中的缺乏JAHN蛋白胨效应

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This work attempts to unveil the similarities and differences between Jahn-Teller (JT) and non-JT systems involving CuF64- units. For achieving this goal, we firstly explore Na2CuF4 and NaF:Cu2+ systems through first principles calculations and pay particular attention to the links between JT and non-JT systems looking at the electronic density of the hole. The results on Na2CuF4 in the monoclinic P2(1)/c space group and also in the parent Pbam structure reveal that the local geometry can be understood as an initial tetragonally compressed CuF64- unit, followed by an additional orthorhombic instability that excludes the JT effect as the origin. Although the present results on NaF:Cu2+ underpin an elongated equilibrium geometry such as that measured for Cu2+ ions in the cubic perovskite KZnF3, the force constant for NaF:Cu2+ is half that for KZnF3:Cu2+. This crucial fact is direct proof of the elastic decoupling of CuF64- from the NaF lattice leading to a JT energy, E-JT, which is twice that found for KZnF3:Cu2+. However, both systems have practically the same linear electron-vibration coupling constant, V-1e, a relevant fact whose origin is discussed. The final aim of this work concerns the influence of tetragonal and orthorhombic distortions as well as the internal electric field on the A(1g)-B-1g energy gap, Delta, of a variety of systems with CuF64- complexes. Interestingly, it is shown that compounds with orthorhombic instability and an internal electric field can have a Delta value comparable to the JT system NaF:Cu2+. Accordingly, explanations for optical spectra of transition metal compounds based on simple parameterized models can be meaningless. The present study shows that properties displayed by d(9) compounds in low symmetry lattices can hardly stem from a static JT effect.
机译：这项工作试图揭示Jahn-Teller（JT）和涉及CUF64的非JT系统之间的相似性和差异。为了实现这一目标，我们首先通过第一个原则计算来探索Na2Cuf4和NAF：CU2 +系统，并特别注意看着孔的电子密度的JT和非JT系统之间的链接。 Na2Cuf4在单斜斜液P2（1）/ C空间组中的结果以及在母体PBAM结构中揭示了局部几何形状可以理解为初始四边形压缩的Cu64-单元，其次是额外的正交不稳定性，不包括JT效应作为起源。尽管NAF的目前结果：Cu2 +支撑着细长的平衡几何形状，例如在立方钙钛矿KZNF3中测量的Cu 2 +离子，NAF的力常数：Cu 2 +为KNF 3：Cu 2 +的一半。这种至关重要的事实是Cuf64的弹性去耦的直接证明，从NAF格子导致JT Energy，E-JT，这是KZNF3：Cu2 +的两倍。然而，两个系统实际上具有相同的线性电子振动耦合常数，V-1E，讨论其来源的相关事实。这项工作的最终目的涉及四边形和正交变形以及具有CUF64-复合物的各种系统的A（1G）-B-1G能量间隙中的内部电场的影响。有趣的是，结果表明，具有正交不稳定和内部电场的化合物可以具有与JT系统NAF：Cu2 +相当的Δ值。因此，基于简单的参数化模型的过渡金属化合物的光谱的说明可能是毫无意义的。本研究表明，D（9）低对称晶格中的D（9）化合物显示的性质几乎不能源于静态JT效应。

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    Sanchez-Movellan I.; Aramburu J. A.; Moreno M.;

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    Univ Cantabria Dept Ciencias Tierra &

    Fis Mat Condensada Ave Castros S-N Santander 39005 Spain;

    Univ Cantabria Dept Ciencias Tierra &

    Fis Mat Condensada Ave Castros S-N Santander 39005 Spain;

    Univ Cantabria Dept Ciencias Tierra &

    Fis Mat Condensada Ave Castros S-N Santander 39005 Spain;

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  • 正文语种 eng
  • 中图分类 物理学;化学;
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