论文标题
在一体密度矩阵函数中引入筛选：对扩展Koopmans定理的模型系统激发的影响
Introducing screening in one-body density matrix functionals: impact on the Extended Koopmans' Theorem's charged excitations of model systems
论文作者
论文摘要
在这项工作中，我们深入了解了使用扩展的Koopmans定理（EKT）获得的减少密度矩阵功能对去除/加法质量的影响。在降低的密度基质功能理论（RDMFT）中，EKT方法还原为基质对角线化，其成分是单体和两体降低的密度矩阵。 RDMFT内EKT的一个惊人特征是，它在强相关的材料中打开了一个带隙，尽管太大，这对于GW等最新方法是一个挑战。使用一维Hubbard模型和均质电子气体作为测试用例，我们发现：i）具有精确或非常准确的密度矩阵，将EKT系统地高估了Hubbard模型中的带隙和均质电子气体中的带宽； ii）具有近似密度矩阵，而EKT可以从取消误差中受益。特别是，我们测试了一个新的近似值，该近似结合了RPA筛选与Sharma等人引入的两体还原密度矩阵的功率函数（PF）近似。 [物理。 Rev. B 78，201103（R）（2008）]。该近似值的一个重要特征是它减少了研究模型中的EKT带隙。因此，这可能是校正强相关材料中EKT带隙高估的有希望的近似值。
In this work we get insight into the impact of reduced density matrix functionals on the quality of removal/addition energies obtained using the Extended Koopmans' Theorem (EKT). Within reduced density matrix functional theory (RDMFT) the EKT approach reduces to a matrix diagonalization, whose ingredients are the one- and two-body reduced density matrices. A striking feature of the EKT within RDMFT is that it opens a band gap, although too large, in strongly correlated materials, which are a challenge for state-of-the-art methods such as GW . Using the one-dimensional Hubbard model and the homogeneous electron gas as test cases, we find that: i) with exact or very accurate density matrices the EKT systematically overestimates the band gap in the Hubbard model and the bandwidth in the homogeneous electron gas; ii) with approximate density matrices, instead, the EKT can benefit from error cancellation. In particular we test a new approximation which combines RPA screening with the Power functional (PF) approximation to the two-body reduced density matrix introduced by Sharma et al. [Phys. Rev. B 78, 201103(R) (2008)]. An important feature of this approximation is that it reduces the EKT band gap in the studied models; it can hence be a promising approximation for correcting the EKT band-gap overestimation in strongly correlated materials.
