Physics Department, La Sapienza-University of Rome, Rome, Italy.
J Chem Phys. 2012 Sep 21;137(11):114107. doi: 10.1063/1.4752398.
The description of the electronic structure and magnetic properties of multi-centers transition metal complexes, especially of mixed-valence compounds, still represents a challenge for density functional theory (DFT) methods. The energies and the geometries of the correctly symmetrized low-spin ground state are estimated using the Heisenberg-Dirac-van Vleck spin Hamiltonian within the extended broken symmetry method introduced by Marx and co-workers [Nair et al., J. Chem. Theory Comput. 4, 1174-1188 (2008)]. In the present work we extend the application of this technique, originally implemented using the DFT+U scheme, to the use of hybrid functionals, investigating the ground-state properties of di-iron and di-manganese compounds. The calculated magnetic coupling and vibrational properties of ferredoxin molecular models are in good agreements with experimental results and DFT+U calculations. Six different mixed-valence Mn(III)-Mn(IV) compounds have been extensively studied optimizing the geometry in low-spin, high-spin, and broken-symmetry states and with different functionals. The magnetic coupling constants calculated by the extended broken symmetry approach using B3LYP functional presents a remarkable agreement with the experimental results, revealing that the proposed methodology provides a consistent and accurate DFT approach to the electronic structure of multi-centers transition metal complexes.
多中心过渡金属配合物，特别是混合价化合物的电子结构和磁性质的描述仍然是密度泛函理论（DFT）方法的一个挑战。采用 Marx 等人引入的扩展破对称方法中的海森堡-狄拉克-范弗莱克自旋哈密顿量，估计了正确对称化的低自旋基态的能量和几何形状[Nair 等人，J. Chem. Theory Comput. 4, 1174-1188（2008）]。在本工作中，我们将这项技术的应用扩展到了杂化泛函的使用上，研究了二铁和二锰化合物的基态性质。铁氧还蛋白分子模型的计算磁耦合和振动性质与实验结果和 DFT+U 计算吻合良好。对六种不同的混合价 Mn(III)-Mn(IV)化合物进行了广泛研究，在低自旋、高自旋和破对称状态下以及使用不同的泛函对其进行了几何优化。使用 B3LYP 泛函的扩展破对称方法计算的磁耦合常数与实验结果非常吻合，表明所提出的方法为多中心过渡金属配合物的电子结构提供了一种一致且准确的 DFT 方法。
