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

Journal Article · Mon Jun 21 00:00:00 EDT 2021 · Physical Review Materials

DOI:https://doi.org/10.1103/physrevmaterials.5.063803· OSTI ID:1853746

Neupane, Bimal  ^[1]; Tang, Hong ^[1]; Nepal, Niraj K. ^[1]; Adhikari, Santosh ^[1]; Ruzsinszky, Adrienn ^[1]

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1. Temple Univ., Philadelphia, PA (United States)

The quasiparticle band structure can be properly described by Hedin's GW approximation (GW), at a high computational cost. For band gaps, semilocal density functionals up to the generalized gradient approximation (GGA) level cannot compete with the accuracy of hybrid-based approximations or GW. Meta-GGA density functionals with a strong dependence on the kinetic energy density ingredient can potentially give wider band gaps compared with GGAs. The recent TASK meta-GGA density functional from Aschebrock and Kümmel [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. Additionally, the reduced screening of these materials results in larger band gaps compared with their bulk counterparts, as an additional barrier to overcome. In this paper we demonstrate how the alteration of this functional affects the band gaps of monolayers and nanoribbons and present accurate band gaps competing with the revised Heyd-Scuseria-Ernzerhof (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 and (b) by changing the limit of the interpolation function $f_X(\alpha \to \infty$) of the TASK functional that interpolates the exchange enhancement factor $F_X(s,\alpha )$ from $\alpha =0$ to 1. The resulting modified TASK (mTASK) was tested for various materials from three dimensions to two dimensions to one dimension (nanoribbons) and was compared with the results of the higher-level hybrid functional HSE06 or with the ${\mathrm{G}}_0{\mathrm{W}}_0$ approximation within many-body perturbation theory. We find that mTASK systematically improves the band gaps and band structures of two-dimensional (2D) and 1D systems, without significantly affecting the accuracy of the original TASK for the bulk 3D materials, when compared with the Perdew-Burke-Ernzerhof (PBE) GGA and the strongly constrained and appropriately normed (SCAN) meta-GGA. We further demonstrate the applicability of mTASK by assessing the band structures of transition metal dichalcogenide nanoribbons with respect to various bending curvatures.

• Research Organization: Temple Univ., Philadelphia, PA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); US Army Research Office (ARO); National Science Foundation (NSF)
• Grant/Contract Number: SC0021263; W911NF-16-2-0189; 1625061
• OSTI ID: 1853746
• Journal Information: Physical Review Materials, Vol. 5, Issue 6; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Band gap
Density functional theory