PbTe的内在缺陷化学和自掺杂:第一性原理计算

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热电材料（能将热直接转换为电能，反之亦然）需要掺杂来提高其热电转换效率，而掺杂本质上受限于内在缺陷化学，可通过计算对固有缺陷化学和自掺杂作原子级精确预测。因强烈的自旋-轨道相互作用导致的窄带隙系统的建模却困难重重，尤其是出现自旋-轨道耦合效应（改变能带位置）时，更是无能为力。来自美国科罗拉多矿业大学的Goyal和Stevanovi'c等采用第一原理的密度泛函理论，准确模拟了PbTe的点缺陷。他们发现，PbTe缺陷的精确建模，需要组合自旋-轨道耦合杂化函数和Green函数理论。具有自旋-轨道耦合的杂化HSE函数与G0W0带边偏移计算组合，是唯一无需实验数据输入，既可以精确捕获PbTe中随着合成条件的变化导致的本征导电类型，又可以测定载流子浓度的方法。本研究结果确认了单个带边位置在缺陷计算中的关键作用，并证实在这种极具挑战性的窄带隙材料中，可用其准确预测可掺杂性。本文近期发表于npj Computational Materials 3: 42 (2017);
doi:10.1038/s41524-017-0047-6; 标题与摘要如下，论文PDF文末点击阅读原文可以获取。

First-principles calculation of intrinsic defect chemistry and self-doping in PbTe

(第一性原理计算PbTe的内在缺陷化学和自掺杂)

Anuj Goyal, Prashun Gorai, Eric S. Toberer & Vladan Stevanovi'c

Semiconductor dopability is inherently limited by intrinsic defect chemistry. In many thermoelectric materials, narrow band gaps due to strong spin–orbit interactions make accurate atomic level predictions of intrinsic defect chemistry and self-doping computationally challenging. Here we use different levels of theory to model point defects in PbTe, and compare and contrast the results against each other and a large body of experimental data. We find that to accurately reproduce the intrinsic defect chemistry and known self-doping behavior of PbTe, it is essential to (a) go beyond the semi-local GGA approximation to density functional theory, (b) include spin–orbit coupling, and (c) utilize many-body GWtheory to describe the positions of individual band edges. The hybrid HSE functional with spin–orbit coupling included, in combination with the band edge shifts fromG0W0is the only approach that accurately captures both the intrinsic conductivity type of PbTe as function of synthesis conditions as well as the measured charge carrier concentrations, without the need for experimental inputs. Our results reaffirm the critical role of the position of individual band edges in defect calculations, and demonstrate that dopability can be accurately predicted in such challenging narrow band gap materials.