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

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.