Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
J Chem Phys. 2012 Jun 14;136(22):224101. doi: 10.1063/1.4722552.
The computation of antiferromagnetic exchange coupling constants J by means of efficient density-based approaches requires in practice to take care of both spin projection to approximate the low spin ground state and proper localization of the magnetic orbitals at the transition metal centers. This is demonstrated here by a combined approach where the extended broken-symmetry (EBS) technique is employed to include the former aspect, while spin density constraints are applied to ensure the latter. This constrained EBS (CEBS) approach allows us to carry out ab initio molecular dynamics on a spin-projected low spin potential energy surface that is generated on-the-fly by propagating two coupled determinants and thereby accessing the antiferromagnetic coupling along the trajectory. When applied to the prototypical model of the oxidized [2Fe-2S] cofactor in Ferredoxins, Fe(2)S(2)(SH)(4), at room temperature, CEBS leads to remarkably good results for geometrical structures and coupling constants J.
通过高效的密度泛函方法计算反铁磁交换耦合常数 J，实际上需要兼顾自旋投影以近似低自旋基态，以及在过渡金属中心处适当定位磁轨道。通过组合方法可以实现这一点，其中扩展的破对称（EBS）技术用于包含前一方面，同时应用自旋密度约束来确保后者。这种约束 EBS（CEBS）方法允许我们在由传播两个耦合行列式实时生成的自旋投影低自旋势能表面上进行从头算分子动力学，从而沿着轨迹获取反铁磁耦合。当应用于 Ferredoxins 中氧化 [2Fe-2S] 辅因子的原型模型 Fe(2)S(2)(SH)(4) 时，CEBS 为几何结构和耦合常数 J 提供了非常好的结果。
