Center for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom.
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Chem Phys. 2017 Feb 28;146(8):084113. doi: 10.1063/1.4974929.
Projection-based embedding provides a simple and numerically robust framework for multiscale wavefunction-in-density-functional-theory (WF-in-DFT) calculations. The approach works well when the approximate DFT is sufficiently accurate to describe the energetics of the low-level subsystem and the coupling between subsystems. It is also necessary that the low-level DFT produces a qualitatively reasonable description of the total density, and in this work, we study model systems where delocalization error prevents this from being the case. We find substantial errors in embedding calculations on open-shell doublet systems in which self-interaction errors cause spurious delocalization of the singly occupied orbital. We propose a solution to this error by evaluating the DFT energy using a more accurate self-consistent density, such as that of Hartree-Fock (HF) theory. These so-called WF-in-(HF-DFT) calculations show excellent convergence towards full-system wavefunction calculations.
基于投影的嵌入为多尺度波函数密度泛函理论 (WF-in-DFT) 计算提供了一个简单且数值稳健的框架。当近似密度泛函理论足够准确地描述低水平子系统的能量和子系统之间的耦合时，该方法效果很好。低水平 DFT 也必须对总密度进行定性合理的描述，在这项工作中，我们研究了模型系统，其中离域误差阻止了这种情况的发生。我们在开壳双自由基体系的嵌入计算中发现了大量误差，其中自相互作用误差导致单占据轨道的虚假离域。我们通过使用更准确的自洽密度（例如 Hartree-Fock (HF) 理论的密度）来评估 DFT 能量来解决此错误。这些所谓的 WF-in-(HF-DFT) 计算显示出与全系统波函数计算非常好的收敛性。
