Theoretical Framework for Modeling Field-Dependent Properties of Molecule-Based Magnetic Materials by using Spin-Flips

使用自旋翻转模拟基于分子的磁性材料的场相关特性的理论框架

• 批准号: 441274206
• 负责人: Dr. Sven Kähler, Ph.D.
• 金额: --
• 依托单位: Department of Chemistry
• 依托单位国家: 德国
• 项目类别: WBP Fellowship
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/441274206?language=en
• 关键词: Theoretical; Framework; Modeling; Field; Dependent

We plan to develop high-accuracy computer models to facilitate the design of new magnetic materials, specifically of single-molecule magnets (SMMs) and of molecular multiferroics (MFs) that display magneto-electric coupling. In SMMs unpaired electrons align their magnetic moments (their spins) to form a magnet. Major advantages of SMMs are their high density of magnetic centers and that their properties can be tuned by the chemical environment. This allows their application in novel data storage materials with up to 10000x higher information density compared to current materials. Also, SMMs can exhibit quantum behavior, allowing their use as qubits, the building blocks of quantum computers.MFs are materials with multiple ferroic properties, i.e. internal properties that can be switched by external influence, such as polarization switchable by an electric field or magnetization switchable by a magnetic field. In MFs with magneto-electric coupling (MEC), magnetic properties may also be switched by electric fields (and vice versa). Electric switching of magnetic properties is highly desirable since it is far easier to generate strong, quickly varying or spatially localized electric fields than magnetic ones. This opens up many applications in novel, smaller and more energy-efficient devices for sensing and for data processing and storage.Both SMMs and MFs rely on precise control over the interactions between spins which currently still require improvement to become application-ready: SMMs suffer from unwanted interactions so that their magnetization only remains stable for short times and at very low temperatures. MFs need stronger MEC for fast and efficient switching. Researchers use theoretical models called spin Hamiltonians to describe spin interactions. We propose a new way to parametrize these models using quantum chemical computations.In quantum chemical calculations on systems with multiple unpaired electrons, it is challenging to take into consideration the many different electron configurations that occur. Our innovation is to apply a spin-flip approach developed by my host Prof. Anna Krylov. Spin-flip calculations use so called high-spin states as a starting point, in which all unpaired electron spins are aligned, thereby forming a single configuration. From there, other important configurations are obtained by flipping individual spins.By calculating the spin Hamiltonian from first-principles, we will not only predict properties of candidate materials before they are synthesized but also identify design principles that optimize spin interactions for desired functionality.

我们计划开发高精度的计算机模型，以促进新的磁性材料，特别是单分子磁体（SMM）和分子多铁性（MF），显示磁电耦合的设计。在SMM中，未成对的电子排列它们的磁矩（它们的自旋）以形成磁体。SMM的主要优点是它们的高密度磁中心，并且它们的性质可以通过化学环境来调节。这使得它们能够应用于新型数据存储材料，与当前材料相比，信息密度高达10000倍。此外，SMM可以表现出量子行为，允许它们用作量子比特，量子计算机的构建块AF是具有多种铁电性质的材料，即可以通过外部影响切换的内部性质，例如可通过电场切换的极化或可通过磁场切换的磁化。在具有磁电耦合（MEC）的MF中，磁性也可以通过电场切换（反之亦然）。磁特性的电切换是非常期望的，因为它比磁电场更容易产生强的、快速变化的或空间局部化的电场。这为新型、更小、更节能的传感、数据处理和存储设备开辟了许多应用。SMM和MF都依赖于对自旋之间相互作用的精确控制，目前仍需要改进才能应用：SMM受到不必要的相互作用的影响，因此它们的磁化只能在很短的时间内和很低的温度下保持稳定。MF需要更强的MEC以实现快速有效的切换。研究人员使用称为自旋哈密顿的理论模型来描述自旋相互作用。我们提出了一种新的方法来参数化这些模型使用量子化学计算。在量子化学计算的系统与多个未成对电子，这是具有挑战性的，考虑到许多不同的电子配置发生。我们的创新之处在于采用了由我的东道主安娜·克雷洛夫教授开发的自旋翻转方法。自旋翻转计算使用所谓的高自旋态作为起点，其中所有未成对电子自旋对齐，从而形成单一配置。通过从第一性原理计算自旋哈密顿量，我们不仅可以在合成候选材料之前预测它们的性质，还可以确定优化自旋相互作用以实现所需功能的设计原则。