In high-temperature density functional theory simulations (from tens of eV to keV), the total number of Kohn–Sham orbitals is a critical quantity to get accurate results. To establish the relationship between the number of orbitals and the level of occupation of the highest energy orbital, we derived a model based on the homogeneous electron gas properties at finite temperature. This model predicts the total number of orbitals required to reach a given level of occupation and, thus, a stipulated precision. Levels of occupation as low as ${10}^{-4}$, and below, must be considered to get converged results better than 1%, making high-temperature simulations very time consuming beyond a few tens of eV. After assessing the predictions of the model against previous results and Abinit minimizations, we show how the extended FPMD method of Zhang et al. [Phys. Plasmas 23, 042707 (2016)] allows us to bypass these strong constraints on the number of orbitals at high temperature.

中文翻译：

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高温Kohn-Sham DFT模拟的要求以及如何绕过它们

在高温密度泛函理论模拟（从数十eV到keV）中，Kohn–Sham轨道的总数是获得准确结果的关键量。为了建立轨道数与最高能量轨道的占据水平之间的关系，我们基于有限温度下的均匀电子气性质推导了一个模型。该模型可预测达到给定占领水平所需的轨道总数，从而可预测规定的精度。职业水平低至${10}^{-4}$，及以下，必须考虑以获得大于1％的收敛结果，从而使高温模拟非常耗时，超过几十eV。在根据先前的结果和A binit最小化评估模型的预测后，我们展示了Zhang等人的扩展FPMD方法。[物理 等离子体23，042707（2016）]使我们能够旁路上在高温下轨道数这些强约束。