论文标题
在自我能力嵌入理论框架内测试GFCCSD杂质求解器
Testing the GFCCSD impurity solver on real materials within the self-energy embedding theory framework
论文作者
论文摘要
我们将绿色功能耦合群集单打和双打（GFCCSD）（GFCCSD）应用于对自我能源嵌入理论（SEET）框架中强相关的固体产生的现实杂质问题。我们描述了我们的GFCC求解器实现的细节，研究其性能，并在自洽的SEET中为抗铁磁mno和promagagnetic srmno $ _ {3} $强调了潜在的优势和问题。 GFCCSD为弱和中等相关的杂质提供了令人满意的描述，这些杂质具有通过现有的精确杂质求解器（例如精确的对角线化）（ED）而棘手的大小。但是，我们的数据还表明，当相关性变得较强时，GFCC中使用的单打和加倍近似可能会导致在寻找杂质问题中存在的粒子数时不稳定性。当杂质大小变大，并且存在具有很强相关性的多个退化轨道时，这些不稳定性显得特别严重。我们得出的结论是，要充分检查GFCCSD结果的可靠性，并在没有实验的情况下将它们全面使用{\ em ab instib}计算，则必须对具有高阶激发的GFCC求解器进行验证。
We apply the Green's function coupled cluster singles and doubles (GFCCSD) impurity solver to realistic impurity problems arising for strongly correlated solids within the self-energy embedding theory (SEET) framework. We describe the details of our GFCC solver implementation, investigate its performance, and highlight potential advantages and problems on examples of impurities created during the self-consistent SEET for antiferromagnetic MnO and paramagnetic SrMnO$_{3}$. GFCCSD provides satisfactory descriptions for weakly and moderately correlated impurities with sizes that are intractable by existing accurate impurity solvers such as exact diagonalization (ED). However, our data also shows that when correlations become strong, the singles and doubles approximation used in GFCC could lead to instabilities in searching for the particle number present in impurity problems. These instabilities appears especially severe when the impurity size gets larger and multiple degenerate orbitals with strong correlations are present. We conclude that to fully check the reliability of GFCCSD results and use them in fully {\em ab initio} calculations in the absence of experiments, a verification from a GFCC solver with higher order excitations is necessary.
