单原子填充方钴矿热电材料微观力学行为的分子动力学模拟研究

Filled skutterudites, i.e., partially filling the intrinsic crystal voids of skutterudites with various filler atoms, is a class of novel medium-temperature thermoelectric materials. It is sufficiently understood that the inducing of filler atoms can realize the collaborative controlling of electric and thermal transport, and thus significantly promote the thermoelectric performances. However, the effect of atom filling on the mechanical behavior of skutterudites is not very clear so far. The present program aims to reveal the impact pattern and its physical mechanism of single filling on the mechanical behavior of crystalline skutterudites, for the three typical single-filled (alkali metal, alkaline-earth metal, and rare-earth metal) skutterudites. The interatomic interaction features between the filling atoms and the host atoms, and the impact of inducing filling atoms on the interatomic interactions of host atoms are studied, then the interatomic potentials are constructed to carry out the molecular dynamics simulations. The mechanical behavior of filled crystalline skutterudites is obtained at different temperatures. The impact pattern and its physical mechanism of single filling of different filling atoms or different filling fractions on the intrinsic mechanical performances of skutterudites are revealed. The effect of microdefects on the mechanical behavior of skutterudites is explored as well. The results are expected to provide mechanical foundations for developing high-performance filled skutterudites.

填充式方钴矿是通过在方钴矿化合物的本征晶格孔洞中部分填充杂质原子的一类最具应用价值的中温热电材料。已有的研究表明，填充原子的引入可实现电热输运的协同调控，从而大幅度提高方钴矿的热电性能，但填充原子的引入对方钴矿力学行为的影响规律目前尚不明确。本项目以三类典型原子（碱金属、碱土金属与稀土金属原子）单填充方钴矿晶体为研究对象，以揭示单原子填充对方钴矿晶体力学行为的影响规律及其物理机制为目标，研究填充原子与框架原子之间的相互作用特性和填充原子的引入对框架原子之间相互作用的影响，以此建立填充式方钴矿晶体的原子间作用势，发展分子动力学模拟方法，获得填充式方钴矿晶体在不同温度下的力学行为，研究填充原子种类和填充量对单原子填充方钴矿热电材料本征力学性能的影响规律及其物理机制，并探索微缺陷对材料力学性能的影响规律，为发展高性能填充方钴矿热电材料奠定力学基础。

方钴矿是一类具有潜在应用价值的新型中温热电材料。为了提高综合热电性能，人们提出以杂质原子在方钴矿化合物的本征晶格孔洞中部分填充为基础的结构调控方法。本项目以方钴矿热电材料的典型代表CoSb3为研究对象，发展了二元CoSb3和填充CoSb3的分子动力学模拟及分析方法。由于原子间相互作用势是分子动力学模拟的基础问题，建立了能够描述CoSb3化合物原子间相互作用的作用势模型。围绕单晶块体CoSb3的热-力学性能开展了一系列的研究工作，获得了理想结构及含缺位或纳米孔洞CoSb3在单轴拉伸和压缩时的基本力学性能。同时对理想满填充CoSb3的基本力学行为进行了研究，获得单原子填充CoSb3的力学行为。通过密度泛函理论计算研究了方钴矿热电材料的脆性断裂机制。这些研究成果为方钴矿类热电材料的推广应用奠定了理论基础。