Knowing the electronic structure of a material is essential in energy applications to rationalize its performance and propose alternatives. Materials for thermoelectric applications are generally small-gap semiconductors and should have a high figure of merit ZT. Even if the Fe2VAl Heusler compound has a decent ZT, its conductive nature (semi-metal or semiconductor) is not yet clarified especially at low temperature. In this paper, we focus our DFT calculations on the effect of temperature on the bandgap of Fe2VAl. In contrast to what is usually observed, we show that both the temperature increase and the formation of thermally-activated Al/V inversion defects (observed experimentally), open the bandgap. Such an unusual behavior is the key for reconciling all bandgap measurements performed on the Fe2VAl compound using a standard GGA functional and could be an efficient way for improving the thermoelectric properties of this family of materials.

中文翻译：

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Fe2VAl Heusler 化合物的带隙意外增加

在能源应用中，了解材料的电子结构对于使其性能合理化并提出替代方案至关重要。用于热电应用的材料通常是小间隙半导体，应该具有高品质因数 ZT。即使 Fe2VAl Heusler 化合物具有不错的 ZT，其导电性质（半金属或半导体）尚未明确，尤其是在低温下。在本文中，我们将 DFT 计算重点放在温度对 Fe2VAl 带隙的影响上。与通常观察到的相反，我们表明温度升高和热激活的 Al/V 反转缺陷的形成（通过实验观察）都会打开带隙。