Abstract
We discuss self-consistently obtained ground-state electronic properties of monolayers of graphene and a number of ’beyond graphene’ compounds, including films of transition-metal dichalcogenides (TMDs), using the recently proposed strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (meta-GGA) to the density functional theory. The SCAN meta-GGA results are compared with those based on the local density approximation (LDA) as well as the generalized gradient approximation (GGA). As expected, the GGA yields expanded lattices and softened bonds in relation to the LDA, but the SCAN meta-GGA systematically improves the agreement with experiment. Our study suggests the efficacy of the SCAN functional for accurate modeling of electronic structures of layered materials in high-throughput calculations more generally.
Highlights
The need for theoretical methods capable of accurate and efficient prediction of structural and electronic properties of atomically thin films and layered materials is clear
We present ground-state structural and electronic properties of a series of free-standing monolayer (ML) materials, which are: graphene, silicene, germanene and phosphorene, transition-metal dichalcogenides (TMDs) monolayers MX2 in the semiconducting 2H phase[40] (M =Mo, W; X =S, Se, Te), and one quintuple layer (QL) film of Bi2Se3
We tested how strongly constrained and appropriately normed (SCAN) performs compared to the local density approximation (LDA) and PBE-generalized gradient approximation (GGA) by calculating the lattice constants a, the nearest-atom bond lengths d for graphene, silicene, germanene and phosphorene, the buckling heights Δfor silicene, germanene and phosphorene, and X-M distances dM−X for the TMD monolayers (Fig. 2)
Summary
Materials using SCAN meta-GGA, an Accurate Nonempirical Density received: 19 October 2016 accepted: 14 February 2017. The need for theoretical methods capable of accurate and efficient prediction of structural and electronic properties of atomically thin films and layered materials is clear In this connection, improvements in density functional theory (DFT)[12] based first-principles computations, which have been the workhorse in the field for over five decades[13,14], have centered around the development of new classes of exchange-correlation functionals. We show that SCAN meta-GGA yields a systematic improvement over the LDA and GGA (at a comparable cost) in modeling ground state properties of 2D materials For this purpose, we consider the application of SCAN to monolayers of graphene and a number of ‘beyond graphene’ compounds, including films of transition-metal dichalcogenides (TMDs) as exemplar 2D systems. We describe the relevant computational details, followed by a presentation and discussion of our results, and a summary of our conclusions
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