Temperature-dependent transport properties of solids from first principles

功能材料的许多物理性质都与温度相关，部分是通过固体中原子振动的温度依赖性来实现的。一个典型的例子是热电材料，它可以使用固态半导体器件将热量转化为电能，而无需任何移动部件。原子振动及其温度依赖性影响热电材料的所有关键特性——电导率和塞贝克系数以及电子和晶格对热导率的贡献。尽管如此，绝大多数第一原理电子结构计算都是基于静态晶格、零开尔文计算。该项目的目的是根据第一原理模拟有限温度下晶格振动对半导体（特别是热电材料）电子结构和电子输运特性的影响。该项目将探索和测试最新理论和软件开发的能力和局限性，这些理论和软件开发已提供给研究界，例如在 abinit 项目中。一个中心目标是对半导体电子带隙随温度的变化做出可靠的预测，这是一个关键因素，迄今为止要么被完全忽略，要么从可用的实验数据中获取。这里要研究的候选系统包括硒化锡（SnSe）和碲化铅（PbTe）。这些与温度相关的模拟可以扩展到还包括应力和高压的影响。总体而言，该项目将有助于改善能源应用新材料的计算研究和筛选。

Many physical properties of functional materials are temperature-dependent, in part through the temperature dependence of the atomic vibrations in solids. A case in point are thermoelectric materials, which can be used to convert heat into electricity using solid-state semiconductor devices without any moving parts. Atomic vibrations and their temperature dependence affect all key properties of a thermoelectric material - electrical conductivity and Seebeck coefficient as well as the electronic and lattice contributions to the thermal conductivity. Despite this, the vast majority of first-principles electronic structure calculations are based on static-lattice, zero-kelvin calculations.The aim of this project is to model, from first principles, the effect of lattice vibrations at finite temperatures on the electronic structure and electronic transport properties of semiconductors, in particular thermoelectric materials. The project will explore and test the capabilities and limits of recent theory and software developments, which have been made available to the research community, e.g., in the abinit project. A central aim will beto make reliable predictions of the variation of the electronic band gap of semiconductors with temperature, a key factor that has so far been either ignored altogether or taken from experimental data where available. Candidate systems to be studied here include tin selenide, SnSe, and lead telluride, PbTe. These temperature-dependent simulations may be extended to also include effects of stresses and high pressure. Overall, this project will contribute towards improving the computational study and screening of new materials for energy applications.