Ab initio calculation of the ferromagnetic interaction in a copper-vanadyl oxide (CuIIVIIO) heterodinuclear system
Ab initio calculation of the ferromagnetic interaction in a copper-vanadyl oxide (CuIIVIIO) heterodinuclear system
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铜-氧钒 (CuIIIVIIO) 异双核体系中铁磁相互作用的从头算
DOI：
10.1021/ja00225a015
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发表时间：
1988
影响因子：
15
通讯作者：
O. Kahn
中科院分区：
文献类型：
--
作者：
P. Loth;P. Karafiloglou;J. Daudey;O. Kahn
异双核化合物CuVO (fsa) 2en-CH3OH，其中（fsa） 2en4”是由希夫碱A？A′-（2-羟基-3-羧基苄基）- 1,2 -二氨基乙烷是交换耦合体系的经典例子，实验中观察到的铁磁相互作用（单重态-三重态分裂J= 120 cm-1）归因于磁轨道的严格正交性。为了详细说明这一现象的机理，在具有Cs对称的稍微理想化的分子结构上，用从头算法计算了J。利用赝势对开壳体系进行了从头算SCF-MO计算，得到了这两个磁轨道。正如预期的那样，以铜（Il）为中心的磁轨道相对于镜面是不对称的，而以钒（IV）为中心的磁轨道相对于镜面是对称的。通过对组态相互作用问题的摄动展开，直接得到了J。一阶电位交换项2A" ab为623 cm" 1。二阶动力学交换项恰好为零，因为磁轨道不像Cs的不可约表示那样变换。总的来说，二阶项等于-279 cm“1，这不能补偿零阶铁磁的贡献。计算出的J值为+ 344 cm”1。最后，根据我们的计算结果，讨论了用磁轨道严格正交性来设计基态自旋多重性最高的分子体系的策略。分子材料领域的主要挑战之一是在临界温度Tc以下设计基于分子的铁磁有序系统。当晶格内磁中心间相互作用的平衡导致局域磁场的不补偿时，就会出现这种情况
The heterodinuclear compound CuVO (fsa) 2en-CH3OH, where (fsa) 2en4" is the dinucleating ligand derived from the Schiff base A?, A'-(2-hydroxy-3-carboxybenzylidene)-l, 2-diaminoethane, is a classical example of an exchange-coupled system in which the experimentally observed ferromagnetic interaction (singlet-triplet splitting J= 120 cm-1) has been attributed to the strict orthogonality of the magnetic orbitals. In order to specify the mechanism of the phenomenon, J has been calculated in an ab initio scheme on a slightly idealized molecular structure with a Cs symmetry. The two magnetic orbitals havebeen obtained through an ab initio SCF-MO calculation on the open-shell system, using pseudopotentials. As expected, the magnetic orbital centered on copper (Il) is antisymmetric and that centered on vanadium (IV) is symmetric with regard to the mirror plane. J has been directly obtainedby a perturbation expansion of the configuration interaction problem. The first-order potential exchangeterm 2A" ab has been found as 623 cm" 1. The second-order kinetic exchange term is exactly zero due to the factthat the magnetic orbitals do not transform in the same way as the irreducible representation of Cs. Globally, the second-order terms have been found equal to-279 cm" 1, which does not compensatethe zeroth-order ferromagnetic contribution. The calculated J value has been found as+ 344 cm" 1. Finally, the strategy of strict orthogonality of the magnetic orbitals to design molecular systems in which the ground state has the highest spin multiplicity has been discussed in the light of results of our calculation.One of the main challenges in the field of molecular materials is the design of molecule-based systems ordering ferromagnetically below a critical temperature Tc. l~ J Such a situation may occur when the balance of the interactions between the magnetic centers within the crystal lattice leads to a noncompensation of the local