Jeffrey Snyder: 通过费米表面复杂性因子, 高通量搜寻新型热电材料
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电子在固体内的环境相当复杂,但其在原子晶格内仍可视为自由移动。不过在模拟电子的运动和材料的性能时,需要用有效质量代替其真实质量作为参数,以考虑电子受固体内环境的影响。有效质量是电子能带结构方便的描述参量,但其定义有多种方式,每种可描述电子传输的某方面特征,与被模拟的材料特定性质相关。美国西北大学G. Jeffrey Snyder教授等基于第一性原理开展了玻尔兹曼输运计算,模拟不同的电子输运特性。他们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能带结构,发现可用这两种有效质量的比值确定材料费米表面复杂性因子Nv * K *。在简单体系中这一因子取决于费米表面袋的数量(N v *)及体系的各向异性K *,两者都有利于提高材料热电性能。如经典的PbTe就具有较高的Nv * K *。因此,费米表面复杂性因子可用于高通量搜索高性能的新型热电材料。
该文近期发表于npj Computational Materials 3: 7 (2017),标题与摘要如下,论文PDF文末点击阅读原文可以获取。
Effective mass and Fermi surfacecomplexity factor from ab initio band structure calculations
Zachary M Gibbs,Francesco Ricci, Guodong Li, Hong Zhu, Kristin Persson, GerbrandCeder, GeoffroyHautier, AnubhavJain & G.Jeffrey Snyder
The effective mass is a convenientdescriptor of the electronic band structure used to characterize the density ofstates and electron transport based on a free electron model. While effectivemass is an excellent first-order descriptor in real systems, the exact valuecan have several definitions, each of which describe a different aspect ofelectron transport. Here we use Boltzmann transport calculations applied to abinitio band structures to extract a density-of-states effective mass from theSeebeck Coefficient and an inertial mass from the electrical conductivity tocharacterize the band structure irrespective of the exact scattering mechanism.We identify a Fermi Surface ComplexityFactor: Nv * K * from the ratio of these two masses,which in simple cases depends on the number of Fermi surfacepockets ( N v * ) and their anisotropy K*,both of which are beneficial to high thermoelectric performance as exemplifiedby the high values found in PbTe. The Fermi Surface Complexity factor can beused in high-throughput search of promising thermoelectric materials.
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