arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2202.09396cond-mat.mtrl-sci
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准粒子自洽$GW$自能的实空间表示及其在缺陷计算中的应用

Real space representation of the quasiparticle self-consistent $GW$ self-energy and its application to defect calculations

Ozan Dernek, Dmitry Skachkov, Walter R. L. Lambrecht, Mark van Schilfgaarde

摘要:

准粒子自洽QS $GW$方法通过能量无关的厄米特自能矩阵,将准粒子能量从它们的Kohn-Sham密度泛函理论(DFT)本征值修正到DFT本征值中。通过将它们扩展到原子中心的基组(特别是线性化的松饼-锡轨道),自能修正的实空间表示成为可能。我们表明,这种表示是相对短程的。这提供了新的机会,构建一个复杂系统的自能从系统的一部分,通过剪切和粘贴的方法。具体地,对于在大的超晶胞中表示的点缺陷,自能量可以由主体和较小的含缺陷晶胞的自能量构建。周期性宿主的自能可以简单地通过原始细胞的$GW$计算来构建。我们表明的情况下,作为$_\mathrm{Ga}$在GaAs中的缺陷部分已经可以很好地表示由一个最小的8个原子的细胞,并允许我们构建一个64细胞的自能与直接QS $GW$计算的大细胞的良好协议。使用这种方法,一个更大的216个原子的细胞显示的缺陷带接近一个孤立的缺陷水平。计算还允许识别第二缺陷带,其出现为导带最小值附近的共振。提取的缺陷能级的结果与格林函数计算的孤立缺陷和实验数据吻合良好。

英文摘要:

The quasiparticle self-consistent QS$GW$ approach incorporates the corrections of the quasiparticle energies from their Kohn-Sham density functional theory (DFT) eigenvalues by means of an energy independent and Hermitian self-energy matrix usually given in the basis set of the DFT eigenstates. By expanding these into an atom-centered basis set (specifically here the linearized muffin-tin orbitals) a real space representation of the self-energy corrections becomes possible. We show that this representation is relatively short-ranged. This offers new opportunities to construct the self-energy of a complex system from parts of the system by a cut-and-paste method. Specifically for a point defect, represented in a large supercell, the self-eneregy can be constructed from those of the host and a smaller defect containing cell. The self-energy of the periodic host can be constructed simply from a $GW$ calculation for the primitive cell. We show for the case of the As$_\mathrm{Ga}$ in GaAs that the defect part can already be well represented by a minimal 8 atom cell and allows us to construct the self-energy for a 64 cell in good agreement with direct QS$GW$ calculations for the large cell. Using this approach to an even larger 216 atom cell shows the defect band approaches an isolated defect level. The calculations also allow to identify a second defect band which appears as a resonance near the conduction band minimum. The results on the extracted defect levels agree well with Green's function calculations for an isolated defect and with experimental data.

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