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arXiv 2104.04053cond-mat.mtrl-sci
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在密度泛函近似的meta-GGA水平上低维材料的开带

Opening band gaps of low-dimensional materials at the meta-GGA level of density functional approximations

Bimal Neupane, Hong Tang, Niraj K. Nepal, Santosh Adhikari, Adrienn Ruzsinszky

摘要:

最近的任务元GGA密度泛函[Phys. Rev. Research,1,033082(2019)]在广义Kohn-Sham方案中构建了增强的非局域性,因此为带隙预测提供了很大的机会。虽然这种近似被发现产生良好的带隙的散装固体,这种精度不能直接转移到低维材料。这些材料的减少的屏蔽导致与它们的本体对应物相比更大的带隙,作为要克服的额外障碍。在这项工作中,我们演示了如何在此功能的确切物理约束的改变影响的带隙的单层和纳米带,并提出准确的带隙与HSE 06近似竞争。为了实现这一目标,我们修改了ASK泛函(a),将单电子或双电子系统($h_X^0$)的严格上限从1.174更改为1.29(b),通过更改内插交换增强因子$F_X (s,α)$的ASK泛函的内插函数($f_X (α\rightarrow \infty$)的极限从$α=$ 0更改为1。对从3D到2D再到1D(纳米带)的各种材料测试了所得的修改的ASK(mASK),并将其与更高级别的混合功能HSE 06的结果或与多体微扰理论内的G $_0$ W $_0$近似的结果进行了比较。我们发现,与PBE-GGA和SCAN meta-GGA相比,mASK大大提高了2D和1D系统的带隙和能带结构,而不会显著影响原始ASK对大块3D材料的准确性。我们通过评估TMD纳米带相对于各种弯曲曲率的能带结构进一步证明了mASK的适用性。

英文摘要:

The recent TASK meta-GGA density functional [Phys. Rev. Research, 1, 033082 (2019)] is constructed with an enhanced nonlocality in the generalized Kohn-Sham scheme, and therefore harbors great opportunities for band gap prediction. Although this approximation was found to yield excellent band gaps of bulk solids, this accuracy cannot be straightforwardly transferred to low-dimensional materials. The reduced screening of these materials results in larger band gaps compared to their bulk counterparts, as an additional barrier to overcome. In this work, we demonstrate how the alteration of exact physical constraints in this functional affects the band gaps of monolayers and nanoribbons, and present accurate band gaps competing with the HSE06 approximation. In order to achieve this goal, we have modified the TASK functional (a) by changing the tight upper-bound for one or two-electron systems ($h_X^0$) from 1.174 to 1.29 (b) by changing the limit of interpolation function $f_X (α\rightarrow \infty$) of the TASK functional that interpolates the exchange enhancement factor $F_X (s,α)$ from $α=$ 0 to 1. The resulting modified TASK (mTASK) was tested for various materials from 3D to 2D to 1D (nanoribbons), and was compared with the results of the higher-level hybrid functional HSE06 or with the G$_0$W$_0$ approximation within many-body perturbation theory. We find that mTASK greatly improves the band gaps and band structures of 2D and 1D systems, without significantly affecting the accuracy of the original TASK for the bulk 3D materials, when compared to the PBE-GGA and SCAN meta-GGA. We further demonstrate the applicability of mTASK by assessing the band structures of TMD nanoribbons with respect to various bending curvatures.

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