By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem DFT has recently emerged as a powerful tool for reducing the computational scaling of Kohn--Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extening FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dual approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement (but still within chemical accuracy) with Kohn--Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed.
University of Ulm（乌尔姆大学）；Science Institute and Faculty of Physical Sciences, University of Iceland（冰岛大学科学研究所与物理科学学院）；Helmholtz-Institute Ulm for Electrochemical Energy Storage, University of Ulm（乌尔姆亥姆霍兹电化学储能研究所）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）
Koopmans spectral functionals in periodic-boundary conditions
Koopmans光谱泛函旨在同时描述原子、分子、纳米结构和周期晶体的基态性质和带电激发。这是通过用简单但物理动机的轨道密度相关修正来增强标准密度泛函来实现的。这些修正作用于一组定域轨道，在周期系统中，类似于最大定域的Wannier函数。与原始的直接超原胞实现[Phys. Rev. X 8，021051（2018）]不同，我们在这里讨论i）使用显式布里渊区采样的边界码所需的复杂但有效的形式主义，以及ii）使用密度泛函微扰理论计算屏蔽的Koopmans校正。除了提供随系统尺寸的改进的缩放之外，本开发使得利用Koopmans泛函的能带结构的计算简单明了。在开源量子ESTERO分布和应用程序的原型绝缘和半导体系统的实施和讨论。
Density-functional approach to the band gaps of finite and periodic two-dimensional systems
我们提出了一种基于密度泛函理论的方法来计算有限和周期二维（2D）电子系统的基本能隙。我们的方法的计算成本是通过标准的半本地形式进行的总能量计算。我们通过用Guandalini等人[Phys. Rev. B 99，125140（2019）]的程序中的交换势的更复杂但计算简单的轨道相关建模来取代2D局部密度近似来实现这一点。我们展示了半导体二维量子点和人造石墨烯系统的有希望的结果，其中能带结构可以通过，例如，凯库勒失真。
All-electron machine-learned orbital-free density functional for periodic CHNO systems
Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University（海德堡大学跨学科科学计算中心）；Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, University of Edinburgh（爱丁堡大学物理与天文学学院极端条件科学与SUPA中心）
