Molecular static methods for the simulation of ferroelectric materials

用于模拟铁电材料的分子静态方法

• 批准号: 201207895
• 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 Units
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/201207895?language=en
• 关键词: Molecular; static; methods; simulation; ferroelectric

Ferroelectric materials are modelled and simulated on different length scales between the electron structure and the continuum description. Therefore, also atomistic models and algorithms have been developed further in the last decade and attain accurate results.Nevertheless the computational costs of the established atomistic methods are still significant. For that reason atomistic scale simulation methods are further developed.The goal of this project is the development and investigation of molecular static methods for the analysis of electromechanical phenomena on the micro level in ferroelectric materials. Therefore an accurate description of the material on an atomistic scale has to be made to investigate relevant regions, such as domain walls and nanofilms. In order to simulate ferroelectric materials on the micro scale, ab initio methods and molecular dynamics have been used for some time. Yet, not only the small length scale is a limiting factor but also the time step length. Through the use of molecular static methods the dynamic problem shall be transferred to a quasi-static algorithm.In order to simulate ferroelectric materials, the core-shell model is widely used in atomistic simulations. Thereby interactions between atom cores and electron shells are considered by interaction potentials, e.g. the Coulomb potential or the Lennard-Jones potential. The newly developed algorithm has been already used to investigate ferroelectric phenomena, such as domain walls, at the atomistic level. Moreover a new method has been implemented in order to consider macroscopic continuum stresses. Therefore the developed algorithm was able to compute not only the dielectric hysteresis but also the butterfly hysteresis of a ferroelectric crystal.Most molecular static algorithm do not consider temperature. However, in order to simulate phase transitions temperature has to be considered. Therefore a temperature dependent interaction potential has to be included to extend the core-shell model in order to simulate technically relevant structures and phase transitions.In addition to the targeted methodological outcome, the results shall be compared directly to the other projects which use non-atomistic methods for the simulation of ferroelectric materials.

铁电材料的电子结构和连续描述之间的不同长度尺度上建模和模拟。因此，原子模型和算法在过去的十年中也得到了进一步的发展，并获得了准确的结果。然而，所建立的原子方法的计算成本仍然很大。本计画的目标是发展和研究分子静态方法，以分析铁电材料中微观层次的机电现象。因此，必须在原子尺度上对材料进行精确描述，以研究相关区域，例如畴壁和纳米膜。为了在微观尺度上模拟铁电材料，从头算方法和分子动力学已经使用了一段时间。然而，不仅小的长度尺度是限制因素，而且时间步长也是限制因素。利用分子静态方法，可以将动力学问题转化为准静态问题，核壳模型是原子模拟铁电材料的常用方法。因此，原子核和电子壳层之间的相互作用被认为是相互作用势，例如库仑势或Lennard-Jones势。新开发的算法已经被用来研究铁电现象，如畴壁，在原子水平。此外，一种新的方法已经实施，以考虑宏观连续应力。因此，该算法不仅可以计算铁电晶体的介电滞回线，而且可以计算铁电晶体的蝶形电滞回线。然而，为了模拟相变，必须考虑温度。因此，必须包括温度相关的相互作用势，以扩展核壳模型，以模拟技术相关的结构和相变。除了有针对性的方法的结果，结果应直接比较的其他项目，使用非原子的方法模拟铁电材料。