多晶材质电子结构及热电性能的模拟

Simulating electronic states and thermoelectric properties in polycrystallines

发展了一种研究多晶体系电子态以及热电性质的计算机模拟方法。首先采用相场动力学方法模拟多晶材质图案，再利用其模型序参量构造晶界的势函数，用近自由电子近似构造体系的哈密顿量。求解薛定谔方程得到体系的本征态。通过电荷密度的分布研究电子的限域特征,分析模拟结果发现对于晶界为势垒的情况，电子的基态出现在最大晶粒中；而对于晶界为势阱的情况，电子更容易限域在多个晶粒交叉的晶界附近，由得到的本征能级和波函数可以计算出温差导致的电位差，即得到赛贝克系数随温度的变化。结果表明具有导电晶界的多晶体的赛贝克系数要高于具有导电晶粒的多晶体。

A scheme has been developed to simulate the electronic and thermoelectric property of polycrystalline. PolycrystaUine texture is created from phase field method in a two dimension scale at the first step. Afterwards, the grain boundary potential function is created using the order parameters of the phase field, the grain boundaries are assumed as potential barriers or wells. Near free electron model is employed to construct the Hamiltonian. Eigen-values are obtained by solving the schordinger equation numerically. We found that the lowest state electrons are easyly confined at the largest grains or grain boundaries with several grains join together. The Seebeck coefficient has been calculated from the eigen-values. The calculated Seebeck coefficient is larger in polycrystallines with conductive grain boundaries, rather than that with conductive grains.