Electronic structure and magnetic properties of a trigonal prismatic Cu(II)6 cluster.
Electronic structure and magnetic properties of a trigonal prismatic Cu(II)6 cluster.
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DOI：
10.1039/b907805c
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发表时间：
2009-07
影响因子：
4
通讯作者：
E. Zueva;M. Petrova;R. Herchel;Z. Trávníček;R. Raptis;Logesh Mathivathanan;J. McGrady
中科院分区：
文献类型：
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作者：
E. Zueva;M. Petrova;R. Herchel;Z. Trávníček;R. Raptis;Logesh Mathivathanan;J. McGrady
详细的磁化强度研究和电子结构分析相结合，使用破缺对称密度泛函理论来探索的三角棱柱Cu（II）（6）集群的电子结构。六个S = 1/2的顺磁性金属中心的存在产生了S = 3的最大多重数和总共31个M（S）< 3的破缺对称态。计算的高自旋和对称性破缺状态之间的能量差异表示在15个不同的海森堡交换耦合参数，J（ij），和方程求解的最小二乘拟合过程。通过检查引入的误差逐步对称化的哈密顿量，以减少独立的J（ij）的数量，我们到达一个最小的模型，只包含四个不同的J（ij）（三个内部和一个三角间）。然后，计算出的值指导磁化数据的拟合。J（ij）的计算趋势只有在反对称交换包含在模型哈密顿量中时才能重现。该哈密顿量的使用提供了在所有温度和磁场下的磁行为的合理描述。如果使用更简单的各向同性模型哈密尔顿算子，则J（ij）的最佳拟合值由于需要拟合反对称交换主导曲线形状的低温区域而受到损害。
A combination of detailed magnetisation studies and electronic-structure analysis using broken-symmetry DFT is used to explore the electronic structure of a trigonal prismatic Cu(II)(6) cluster. The presence of six paramagnetic metal centres with S = 1/2 gives rise to a maximum multiplicity of S = 3 and a total of 31 broken-symmetry states with M(S) < 3. Computed differences in energy between the high-spin and broken-symmetry states are expressed in terms of the 15 distinct Heisenberg exchange coupling parameters, J(ij), and the equations are solved by a least-squares fitting procedure. By inspection of the errors introduced by progressive symmetrisation of the Hamiltonian to reduce the number of independent J(ij), we arrive at a minimal model containing only four distinct J(ij) (three intra- and one inter-triangular). The computed values then guide the fitting of the magnetisation data. The computed trends in J(ij) can only be reproduced when antisymmetric exchange is included in the model Hamiltonian. The use of this Hamiltonian provides a reasonable description of the magnetic behaviour at all temperatures and fields. If a simpler isotropic model Hamiltonian is used instead, the best fit values of J(ij) are compromised by the need to fit the low-temperature region where antisymmetric exchange dominates the shape of the curve.