monolayer with high stability and a tunable bandgap*

Two dimensional atomic crystals with pentagonal building blocks have attracted extensive interest in recent years. Here, with the help of ab initio calculations based on density functional theory, we report a unique pentagonal structured NiS₂ monolayer in P-42₁m symmetry, named P-NiS₂. Its dynamic stability has been confirmed by phonon mode analysis. Molecular dynamics simulations and total-energy calculations show that this new P-NiS₂ has robust thermal stability and energetically more stable than all other reported NiS₂ monolayer structures. Electronic band structure calculations show that it is a semiconductor with an indirect band gap of 1.94 eV. Furthermore, we find that small strain triggers a transition from the indirect to direct band gap for this P-NiS₂, suggesting its great potential for applications based on strain-engineering techniques.
[Reference] C.-T. Wang and S. Du, Phys. Chem. Chem. Phys., 2020, 22, 7483-7488.