Broken symmetry approach to density functional calculation of zero field splittings including anisotropic exchange interactions
Broken symmetry approach to density functional calculation of zero field splittings including anisotropic exchange interactions
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DOI：
10.1063/1.4828727
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发表时间：
2013-11-14
影响因子：
4.4
通讯作者：
van Wuellen, Christoph
中科院分区：
文献类型：
--
作者：
Kessler, Eva M. V.;Schmitt, Sebastian;van Wuellen, Christoph
进一步发展了对称性破缺方法计算多核过渡金属配合物的零场分裂（或磁各向异性）。提出了一种从对称性破缺密度泛函计算中提取各向异性交换自旋哈密顿参数的方法。对于各向同性交换耦合常数J（ij），恢复了已建立的程序，并类似地得到各向异性（或伪偶极）交换耦合张量D-ij。该过程仅产生各个单离子零场分裂张量Di的和。因此，基于定域轨道的程序已经开发出提取个人的单离子的贡献。与手头的自旋哈密顿参数，零场分裂的个别自旋多重态计算的各向同性部分的精确对角化，然后由数字自旋投影完成。该方法被应用到双核阳离子[LCr（OH）（3）CrL]（3）+（L = 1，4，7-三甲基-1，4，7-三氮杂壬烷）和单分子磁体[Fe-4（CH 3C（CH 2 O）（3））（2）（dpm）（6）]（Hdpm = 2，2，6，6-四甲基庚烷-3，5-二酮）。在这两种三维化合物中，单离子张量主要来自自旋轨道相互作用。各向异性交换是占主导地位的自旋偶极相互作用，只有铬化合物。尽管铁化合物中的各向同性交换耦合相当小，但自旋轨道和自旋偶极对各向异性交换的贡献在这里具有相似的大小。(C)2013 AIP Publishing LLC.
The broken symmetry approach to the calculation of zero field splittings (or magnetic anisotropies) of multinuclear transition metal complexes is further developed. A procedure is suggested how to extract spin Hamiltonian parameters for anisotropic exchange from a set of broken symmetry density functional calculations. For isotropic exchange coupling constants J(ij), the established procedure is retrieved, and anisotropic (or pseudodipolar) exchange coupling tensors D-ij are obtained analogously. This procedure only yields the sum of the individual single-ion zero field splitting tensors D-i. Therefore, a procedure based on localized orbitals has been developed to extract the individual single-ion contributions. With spin Hamiltonian parameters at hand, the zero field splittings of the individual spin multiplets are calculated by an exact diagonalization of the isotropic part, followed by a spin projection done numerically. The method is applied to the binuclear cation [LCr(OH)(3)CrL](3) + (L = 1,4,7-trimethyl-1,4,7-triazanonane) for which experimental zero field splittings for all low-energy spin states are known, and to the single-molecule magnet [Fe-4(CH3C(CH2O)(3))(2)(dpm)(6)] (Hdpm = 2,2,6,6-tetramethylheptane-3,5-dione). In both these 3d compounds, the single-ion tensors mainly come from the spin-orbit interaction. Anisotropic exchange is dominated by the spin-dipolar interaction only for the chromium compound. Despite the rather small isotropic exchange couplings in the iron compound, spin-orbit and spin-dipolar contributions to anisotropic exchange are of similar size here. (C) 2013 AIP Publishing LLC.