Elastic, electronic, and dielectric properties of bulk and monolayer ZrS₂, ZrSe₂, HfS₂, HfSe₂ from van der Waals density‐functional theory

Abstract

The elastic, electronic, and dielectric properties of layered transition metal dichalcogenides MX2 (M = Zr and Hf; X = S, Se) have been investigated using density functional theory (DFT) with van der Waals correction. The elastic modulus indicate that the structures belong to brittle materials. The band gaps of these materials through Heyd–Scuseria–Ernzerhof hybrid functional are in reasonable agreement with the experimental data. Partial density of state analysis suggests that the metallic atoms play a dominant role in the conduction band and the chalcogenide atoms have the main effect on the valence band. The presence of peaks in the dielectric constant spectra mainly result from the transition between first, second, third valence bands and the first conduction bands and the direction is from Γ to M, M to K, and K to Γ of the high symmetry k‐points for bulk and monolayer structures, respectively. What is more, parallel band effect has been observed in monolayer structures, which suggests strong light‐matter interactions in these materials. This work promotes the property understanding of these materials and holds potential for the development of optoelectronic devices based on these layered materials.

2D Group IVB Transition Metal Dichalcogenides

“…Strong similarities are displayed among the band structures of ZrS 2 with different layers, showing that they are all indirect bandgap semiconductors with conduction band minima (CBW) at M and valence band maxima (VBW) at Γ. Identical band structures between monolayer and bulk ZrS 2 were also found in Figure b,c, respectively, which are deduced from density functional theory (DFT) with the vdW correction. Moreover, it revealed a parallel‐band feature of monolayer ZrS 2 that the conduction and valence bands are parallel to each other.…”

“…Band structure of b) monolayer ZrS 2 and c) bulk ZrS 2 by DFT with vdW correction. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

Density Functional Theory Analysis of Electronic and Optical Properties of Two‐Dimensional Tantalum Carbides Tan+1Cn (n = 1, 2, 3)

“…Below 4.0 eV, there are two major peaks at 1.5 and 3.0 eV for Ta 2 C, four major peaks at 0.4, 0.8, 1.7, and 2.8 eV for Ta 3 C 2 , and three major peaks at 0.5, 0.9, and 1.6 eV for Ta 4 C 3 . From the electronic structure, these major peaks mainly originated from the transitions from occupied Ta 5d and C 2p states near the Fermi [26][27][28] Ta nþ1 C n monolayers show obvious discrepancy of the dielectric properties caused by its metallic feature. For TMDs and h-BN, the e 2 (ω) peaks appear only when photon energy exceeds the band gap, which are the absorptive transition from the valence bands to the conduction bands.…”

First‐Principles Calculations of Phonons and Thermodynamic Properties of Zr(Hf)S2‐Based Nanotubes

“…The formation and strain energies are defined as the difference (per formula unit) between the energy of NT and the energy of the bulk crystal and monolayer, respectively: PW [13] HSE06 (GW) PW [16] HSE06 (PBE) PW [26] PBE PW [25] PBE (GW) PW [12] PBE LCAO HSE06 [b] PW [13] HSE06 (GW) PW [16] HSE06 (PBE) PW [26] PBE PW [25] PBE (GW) PW [ …”

“…[1][2][3][4] Particularly, it was demonstrated that nanotubes produced from layered transition metal disulfides MoS 2 and WS 2 exhibit a stable, closed, hollow structure. [6,9,10] The theoretical modeling was carried out in references [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] for bulk Zr(Hf) sulfides and their monolayers. [4,7,8] The ZrS 2 and HfS 2 nanotubes have been synthesized since the early 2000s.…”