Multiscale Modeling and Simulation of Ferroelectric Materials

铁电材料的多尺度建模与仿真

• 批准号: 414986811
• 负责人: Professor Dr.-Ing. Paul Steinmann
• 金额: --
• 依托单位: Lehrstuhl für Technische Mechanik (LTM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/414986811?language=en
• 关键词: Multiscale; Modeling; Simulation; Ferroelectric; Materials

The state of the art in material modeling offers accurate simulation methods for specific length and time scales, spanning from electronic structure calculations and molecular mechanics at atomistic scales to continuum formulations at the macroscale. However, computational costs limit the length and time scales accessible to atomistic simulation techniques. As a noteworthy exception, the quasicontinuum (QC) method reduces computational costs without losing atomistic detail in regions where it is required. Thereby it reduces the number of degrees of freedom by introducing kinematic constraints, which interpolate lattice site positions from the positions of a reduced set of representative atoms. In addition to kinematic constraints, summation rules are introduced to efficiently reduce the number of lattice sites to be considered in the computation of energies and forces. The QC method has proven useful to study exemplary problems in multiscale material modeling such as nanoindentation, interaction of lattice defects with nanosized cracks and nanovoids, etc.However, the established QC method has two central limitations. First, it does not extend satisfactorily to multi-lattice crystals to capture non-uniform behavior within a unit cell or a molecule. Second, and more importantly, it does not extend to ionic crystals, since long-range Coulomb interactions present an additional challenge for the QC method. The QC summation rules take advantage of typical short-range interatomic potentials, which admit the local evaluation of quantities of interest. When long-range interactions gain importance, such a concept no longer applies. This restriction on the nature of atomic-level interactions for the conventional QC method excludes its application to a large class of materials; all dielectrics, polarizable solids, and ionic solids.The QC method, therefore, does not find application to study the rich dielectric behavior of typical functional materials that are central to modern technologies in energy storage, sensing/actuation, etc. Developing and extending the QC method for ionic crystals is thus a significant leap in broadening the applicability of the method. Therefore, through this project we propose a novel extended QC method that is applicable to multi-lattice crystals and ionic crystals thereby overcoming limitations of the established QC method. The preliminary work undertaken at LTM using a QC software developed and implemented in-house shows promising results and indicates that the proposed extended QC method will indeed apply effectively to ionic crystals. Thus in summary, the goals of this project are (i) extension of the QC method to multi-lattice crystalline materials, (ii) extension of the QC method to handle long-range Coulomb interactions, (iii) implementation of these extensions and providing the first open-source library for three-dimensional QC simulations, and (iv) the study of ferroelectric behavior using the extended QC method.

材料建模的最新技术为特定长度和时间尺度提供了精确的模拟方法，从原子尺度上的电子结构计算和分子力学到宏观尺度上的连续体公式。然而，计算成本限制了原子模拟技术的长度和时间尺度。作为一个值得注意的例外，准连续体（QC）方法减少了计算成本，而不会丢失所需区域的原子细节。因此，它通过引入运动学约束来减少自由度的数量，运动学约束从一组简化的代表性原子的位置插入晶格位置。除了运动学约束外，还引入了求和规则，以有效地减少在计算能量和力时需要考虑的点阵点的数量。QC方法已被证明可用于研究多尺度材料建模中的示例性问题，如纳米压痕、晶格缺陷与纳米裂纹和纳米空隙的相互作用等。然而，已建立的QC方法有两个主要局限性。首先，它不能令人满意地扩展到多晶格晶体，以捕获单位细胞或分子内的非均匀行为。其次，更重要的是，它不能扩展到离子晶体，因为远程库仑相互作用对QC方法提出了额外的挑战。QC求和规则利用了典型的短程原子间势，它允许对感兴趣的量进行局部评价。当远程交互变得重要时，这样的概念就不再适用了。传统QC方法对原子水平相互作用性质的限制使其无法应用于大类材料；所有的电介质、极化固体和离子固体。因此，QC方法不适用于研究典型功能材料的丰富介电行为，而这些功能材料是现代储能、传感/驱动等技术的核心。因此，发展和推广离子晶体质量控制方法是拓宽该方法适用性的一个重大飞跃。因此，通过本项目，我们提出了一种适用于多晶格晶体和离子晶体的新型扩展QC方法，从而克服了现有QC方法的局限性。LTM使用内部开发和实施的QC软件进行的初步工作显示出有希望的结果，并表明所提出的扩展QC方法确实可以有效地应用于离子晶体。综上所述，该项目的目标是(i)将QC方法扩展到多晶格晶体材料，（ii）将QC方法扩展到处理远程库仑相互作用，（iii）实现这些扩展并提供第一个用于三维QC模拟的开源库，以及（iv）使用扩展QC方法研究铁电行为。