Ab initio based multiscale simulations of domain structures in thermoelektric materials

基于从头开始的热电材料域结构的多尺度模拟

• 批准号: 220269302
• 负责人: Privatdozent Dr. Thomas Gruhn
• 金额: --
• 依托单位: Lehrstuhl für Biomaterialien
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/220269302?language=en
• 关键词: Ab; initio; based; multiscale; simulations

The reduction of the thermal lattice conductivity is an important objective in the development of new thermoelectric materials. Low lattice conductivities are found in materials with suitable nanostructures. In some compounds such a structure formation occurs spontaneously due to a phase segregation of components. In this project, we use ab-initio based multiscale simulations to study the domain formation and the resulting thermal lattice conductivity of thermoelectric materials that show partial demixing. The focus of the investigations will be on the thermoelectric half-Heusler material CoTi1-xMnxSb, which shows a partial segregation on one of the three sublattices. The simulations provide information about the segregation type and the shape of the domains as a function of the temperature and the stoichiometry of the system. Furthermore, we investigate the dynamics of the domain formation and the thermal lattice conductivity of differently structured materials. The material properties are determined with the help of Monte Carlo simulations and phase field methods. The simulations are based on a cluster expansion of the configurational energy that we derive from quantum mechanical density functional calculations. The Monte Carlo simulations are used to analyze the coexistence region of the alloy. This allows predicting whether a given compound demixes by cluster growth or by spinodal decomposition. Monte Carlo simulations of the domain boundary and its regularity help to determine a material with an optimum phonon damping. The phase field method is used to determine the three-dimensional domain structure on a larger length scale, which is very difficult to investigate, experimentally. The thermal lattice conductivity is calculated for nano and micro-structured materials, showing which domain structures lead to especially low heat conduction. The phase field method is also used to study the dynamics of segregation, which gives information on the persistence of the domain structures. The aim of all the numerical studies is to determine the structural and thermal properties of the compounds as a function of the composition and the production parameters in order to provide guide lines for the development of optimized thermoelectric materials.

降低晶格热导率是开发新型热电材料的重要目标。在具有合适的纳米结构的材料中发现低晶格电导率。在某些化合物中，由于组分的相分离，这种结构的形成自发地发生。在这个项目中，我们使用基于从头算的多尺度模拟来研究显示部分分层的热电材料的畴形成和由此产生的热晶格电导率。调查的重点将是热电半Heusler材料CoTi 1-xMnxSb，它显示了部分偏析的三个子晶格之一。模拟提供了有关偏析类型和形状的域作为温度和化学计量的系统的函数的信息。此外，我们调查的动态域的形成和不同结构的材料的热晶格电导率。的材料属性的Monte Carlo模拟和相场方法的帮助下确定。模拟的基础上，我们来自量子力学密度泛函计算的组态能量的集群扩展。采用Monte Carlo模拟方法对合金的共存区进行了分析。这允许预测给定的化合物是否通过簇生长或通过旋节分解而解混。Monte Carlo模拟的域边界和它的规律性，以帮助确定一个最佳的声子阻尼材料。相场法被用来确定在一个更大的长度尺度上的三维畴结构，这是非常困难的调查，实验。计算了纳米和微米结构材料的热晶格传导率，显示了哪些畴结构导致特别低的热传导。相场方法也被用来研究偏析的动力学，这给出了信息的持续性的域结构。所有数值研究的目的是确定化合物的结构和热性能作为组合物和生产参数的函数，以便为开发优化的热电材料提供指导。