Temperature-dependent transport properties of solids from first principles

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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.