The local spin method suggested previously for defining the spin state of an atom in a molecule is applied to model manganese complexes with three and four manganese centers. This method extracts from the wave function a spin for the manganese centers that has been compared to the one suggested by chemical intuition. Density functional theory (DFT) calculations with various total spin projections in the "up" directions, M, but controlled |M| for each manganese center, gave a set of energies that were fit to the Heisenberg Hamiltonian. The eigenvalues of this model Hamiltonian then predict the ground spin state and the preferred combinations of spin orientations of the manganese centers. In some model complexes, changes in the wave function for each spin solution made the Heisenberg Hamiltonian unsuitable for fitting. For a dinuclear manganese complex, complete active space self-consistent field calculations were performed and are in reasonable agreement with the DFT results.
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机译：先前建议的用于定义分子中原子的自旋态的局部自旋方法可用于模拟具有三个和四个锰中心的锰配合物。该方法从波动函数中提取了锰中心的自旋，该自旋已与化学直觉所建议的自旋进行了比较。在“向上”方向上具有各种总自旋投影的密度泛函理论（DFT）计算，M，但受控的| M |对于每个锰中心，给出了一组适合海森堡哈密顿量的能量。然后，该模型的哈密顿量特征值可预测基态自旋态以及锰中心自旋取向的最佳组合。在某些模型复合物中，每个自旋解的波动函数的变化使海森堡哈密顿量不适合拟合。对于双核锰配合物，进行了完整的活动空间自洽场计算，并且与DFT结果合理地吻合。
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