Ensemble density functional theory (EDFT) is a promising alternative to time-dependent density functional theory for computing electronic excitation energies. Using coordinate scaling, we prove several fundamental exact conditions in EDFT and illustrate them on the exact singlet bi-ensemble of the Hubbard dimer. Several approximations violate these conditions, and some ground-state conditions from quantum chemistry do not generalize to EDFT. The strong correlation limit is derived for the dimer, revealing weight-dependent derivative discontinuities in EDFT.

中文翻译：

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系综密度泛函理论的精确条件

系综密度泛函理论 (EDFT) 是计算电子激发能的瞬态密度泛函理论的一种有前景的替代方案。使用坐标缩放，我们证明了 EDFT 中的几个基本精确条件，并在哈伯德二聚体的精确单线态双系综上说明了它们。一些近似值违反了这些条件，并且量子化学中的一些基态条件不能推广到 EDFT。针对二聚体导出了强相关极限，揭示了 EDFT 中与权重相关的导数不连续性。