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Multiscale Modeling of Molecular Magnets

机译:分子磁体的多尺度建模

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摘要

Here, we present an overview of methods of modeling Molecular Magnets in different length scales. First, we discuss a microscopic model to understand the nature of superexchange interaction in binuclear transition metal complexes of different geometry viz. A-B, A-B-A, B-A-B, linear A-B-A-B, and cyclic A-B-A-B systems. We obtain the quantum phase diagrams along various planes in the parameter space and identify the various model parameters which control the nature of superexchange in these systems. We also obtain contours of effective superexchange constants. In the next section we discuss the method of full symmetry adaptation in Valence Bond method to obtain the low-lying eigenstates of the Heisenberg spin Hamiltonian of large systems. The third part of this article deals with the calculation of the magnetic anisotropy parameters (D_M and E_M) of Single Molecule Magnets (SMMs). We use the single ion anisotropy values to obtain D_M and E_M values of the SMM, using a perturbative approach. We first solve the unperturbed Hamiltonian which is a simple spin Heisenberg Hamiltonian. Then we introduce the perturbing term H_l consisting of the single ion anisotropy. We then solve for the molecular anisotropy parameters by equating two different ways for computing the matrix elements of the perturbation term, from knowledge of the spin-spin correlation functions and the direction of orientation of the single ion anisotropies.
机译:在这里,我们概述了在不同长度范围内对分子磁体建模的方法。首先,我们讨论一个微观模型,以了解不同几何形状的双核过渡金属配合物中超交换相互作用的性质。 A-B,A-B-A,B-A-B,线性A-B-A-B和循环A-B-A-B系统。我们获得了沿参数空间中各个平面的量子相图,并确定了控制这些系统中超交换性质的各种模型参数。我们还获得有效的超交换常数的轮廓。在下一部分中,我们将讨论价键方法中的完全对称自适应方法,以获得大系统的Heisenberg自旋哈密顿量的低层本征态。本文的第三部分讨论了单分子磁体(SMM)的磁各向异性参数(D_M和E_M)的计算。我们使用微扰方法使用单离子各向异性值获得SMM的D_M和E_M值。我们首先解决不受干扰的哈密顿量,这是一个简单的自旋海森堡哈密顿量。然后,我们介绍由单离子各向异性组成的扰动项H_1。然后,通过了解自旋-自旋相关函数和单离子各向异性取向的方向,我们通过等于两种不同的方法来计算微扰项的矩阵元素,从而求解分子各向异性参数。

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