Effective mass and Fermi surface complexity factor from ab initio band structure calculations (基于第一性原理能带计算的有效质量和费米表面复杂因子)
Zachary M. Gibbs, Francesco Ricci, Guodong Li, Hong Zhu, Kristin Persson, Gerbrand Ceder, Geoffroy Hautier, Anubhav Jain & G. Jeffrey Snyder
npj Computational Materials 3, Article number: 8 (2017)
doi:10.1038/s41524-017-0013-3
Published online:23 February 2017
Abstract| Full Text | PDF OPEN 

 

摘要：有效质量是电子带结构方便的描述参量，可用于表征自由电子模型的态密度和电子传输特征。虽然有效质量在实际系统中是优良的一阶描述参量，但其精确值有不同的定义，每种可描述电子传输的某方面特征。本研究基于第一性原理开展了玻尔兹曼运输计算，不考虑确切的散射机制，而从塞贝克系数提取态密度有效质量、从电导率提取惯性质量来表征带结构。我们以这两个质量比值确定了费米表面复杂性因子，即Nv * K *，在简单体系中它取决于费米表面袋的数量（N v *）及体系的各向异性K *，这两方面都有利于提高热电性能，如热电材料PbTe就具有较高的费米表面复杂性因子值。费米表面复杂性因子可用于高通量搜索有前景的热电材料。  

Abstract: The effective mass is a convenient descriptor of the electronic band structure used to characterize the density of states and electron transport based on a free electron model. While effective mass is an excellent first-order descriptor in real systems, the exact value can have several definitions, each of which describe a different aspect of electron transport. Here we use Boltzmann transport calculations applied to ab initio band structures to extract a density-of-states effective mass from the Seebeck Coefficient and an inertial mass from the electrical conductivity to characterize the band structure irrespective of the exact scattering mechanism. We identify a Fermi Surface Complexity Factor: Nv * K * from the ratio of these two masses, which in simple cases depends on the number of Fermi surface pockets ( N v * ) and their anisotropy K^*, both of which are beneficial to high thermoelectric performance as exemplified by the high values found in PbTe. The Fermi Surface Complexity factor can be used in high-throughput search of promising thermoelectric materials.

Editorial Summary

Electronic materials: In search of the right mass (电子材料：寻找合适的质量)

由美国和比利时的研究人员开发了一种用于确定材料热电性能的简单方法。美国西北大学的Snyder及其同事建立的模型，可以简化寻找以废热发电的材料的方法。即便固体内电子的环境非常复杂，电子穿过固体原子晶格的方式仍可看作是在自由空间移动。然而，由于其环境的影响，人们用材料的有效质量，而不是其真实质量，来模拟电子的运动和材料的性能。但有效质量有几种定义方式，与被模拟材料某一性质相关。Snyder等通过对不同电子性质的模拟计算，确定了两种不同有效质量的比值，不仅可用作识别新热电材料的良好方法，还可与电子结构的“复杂性”关联起来。 

A simple method for determining a material’s thermoelectric properties is developed by researchers in the United States and Belgium. Jeffrey Snyder from Northwestern University and his co-workers’ model could simplify the search for materials that efficiently generate electricity from waste heat. Even though the environment of an electron in a solid is very complex, the way an electron moves through a solid’s lattice of atoms can be treated as if it is moving in free space. However, because of the influence of its environment an effective mass, not its true mass, is used to model the movement of electrons and that material’s properties. But this effective-mass can be defined in several ways depending on which material property is being modeled. Snyder et al. determine that the ratio of two different effective masses, as computed from different electronic properties, could be a good method to identify novel thermoelectric materials and can be associated with the “complexity” of the electronic structure

。