Quantum Monte-Carlo and Series-Expansion Analysis of Spin-Models for Molecular Magnets

分子磁体自旋模型的量子蒙特卡罗和级数展开分析

• 批准号: 25514662
• 负责人: Professor Dr. Wolfram Brenig
• 金额: --
• 依托单位: Institut für Theoretische Physik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2006
• 资助国家: 德国
• 起止时间: 2005-12-31 至 2008-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/25514662?language=en
• 关键词: Quantum; Monte; Carlo; Series; Expansion

This project is devoted to thermodynamic, time-dependent, and zero temperature properties of molecular magnets. First, we will analyze the susceptibility and magnetization, of unfrustrated single-molecule magnets (SMM)s which are too large to be handled with present days exact diagonalization (ED) methods. This will be done using the stochastic series expansion (SSE), which is a novel Quantum Monte-Carlo (QMC) simulation method. We intend to improve and adopt the SSE for this purpose. In particular we will apply the SSE to the SMM [Mn9(2POAP-2H)2]6+. Second, we will study the role of dimer-coupling, local anisotropies, and magnetic fields in dimer-ladders as eg. the oxalate systems Na2Me2(C2O4)3(H2O)2, with Me = Mn, Fe, Co, Ni and spin S = (5, 4, 3, 2)/2. This study will be based on the SSE, complemented by an analytic bond-operator theory (BOT). Finally, using a high order series expansion at zero temperature, which is based on an operator renormalization group (ORG) method we will study inter-cluster exchange and spin-frustration in weakly coupled tetra-nuclear molecular magnets. In collaboration with experimental groups the role of inter-tetrahedral exchange on the spin-dynamics of eg. [L2Ni4(N3)(O2CAda)4](CIO4) will be considered.

该项目致力于研究分子磁体的热力学、时间依赖性和零温度特性。首先，我们将分析非受阻单分子磁体 (SMM) 的磁化率和磁化强度，这些磁体太大而无法使用当今的精确对角化 (ED) 方法进行处理。这将使用随机级数展开 (SSE) 来完成，这是一种新颖的量子蒙特卡罗 (QMC) 模拟方法。我们打算为此目的改进和采用上交所。特别是，我们将 SSE 应用于 SMM [Mn9(2POAP-2H)2]6+。其次，我们将研究二聚体偶联、局部各向异性和磁场在二聚体梯中的作用，例如。草酸盐体系 Na2Me2(C2O4)3(H2O)2，其中 Me = Mn、Fe、Co、Ni，自旋 S = (5, 4, 3, 2)/2。本研究将以 SSE 为基础，并辅以分析键算子理论（BOT）。最后，使用基于算子重正化群（ORG）方法的零温高阶级数展开，我们将研究弱耦合四核分子磁体中的簇间交换和自旋挫败。与实验小组合作，研究了四面体间交换对自旋动力学的作用。将考虑[L2Ni4(N3)(O2CAda)4](CIO4)。