Interpretation and Quantification of Magnetic Interaction through Spin Topology.
Interpretation and Quantification of Magnetic Interaction through Spin Topology.
复制标题
通过自旋拓扑解释和量化磁相互作用。
DOI：
10.1021/ct2006506
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发表时间：
2012
影响因子：
5.5
通讯作者：
Anirban Misra
中科院分区：
文献类型：
--
作者：
Satadal Paul;Anirban Misra
这项工作发展了一种形式主义，从基态自旋拓扑结构中量化不成对自旋之间的相互作用。选择自旋通过直接交换和超交换耦合的磁系统作为参考。本文从一般的哈密顿量出发，得到了一个用自旋密度表示的有效哈密顿量，并利用它计算了直接交换磁系统中的交换耦合常数。高自旋低自旋能隙，提取耦合常数，通过密度泛函理论框架内的对称性破缺方法得到。另一方面，采用微扰方法来处理超交换过程。自旋转移之间的交换路径的网站被发现支配的磁性性质的分子执行超交换。金属-配体磁相互作用的估计使用的二级微扰能量的配位体的金属电荷转移和自旋密度的有关网站。使用本形式主义，在超交换过程中的总耦合常数也被划分为从金属配体和金属-金属相互作用的贡献。交换耦合常数的符号和大小，通过本形式主义，被发现是在奇偶校验与使用众所周知的自旋投影技术获得的。此外，在所有的情况下，基态自旋拓扑被发现补充耦合常数的符号。因此，自旋拓扑成为解释交换相互作用本质的一种简单而合乎逻辑的手段。在这种情况下的自旋密度表示类似于麦康奈尔的自旋密度哈密顿量，并反过来验证它。
This work develops a formalism to quantify the interaction among unpaired spins from the ground state spin topology. Magnetic systems where the spins are coupled through direct exchange and superexchange are chosen as references. Starting from a general Hamiltonian, an effective Hamiltonian is obtained in terms of spin density which is utilized to compute exchange coupling constants in magnetic systems executing direct exchange. The high-spin-low-spin energy gap, required to extract the coupling constant, is obtained through the broken symmetry approach within the framework of density functional theory. On the other hand, a perturbative approach is adopted to address the superexchange process. Spin transfer in between the sites in the exchange pathway is found to govern the magnetic nature of a molecule executing superexchange. The metal-ligand magnetic interaction is estimated using the second order perturbation energy for ligand to metal charge transfer and spin densities on the concerned sites. Using the present formalism, the total coupling constant in a superexchange process is also partitioned into the contributions from metal-ligand and metal-metal interactions. Sign and magnitude of the exchange coupling constants, derived through the present formalism, are found to be in parity with those obtained using the well-known spin projection technique. Moreover, in all of the cases, the ground state spin topology is found to complement the sign of coupling constants. Thus, the spin topology turns into a simple and logical means to interpret the nature of exchange interaction. The spin density representation in the present case resembles McConnell's spin density Hamiltonian and in turn validates it.