The air pollutions are the serious subject for the earth

The air pollutions are the serious subject for the earth, right now 1. One of the important matter in modern society is controlling the quantity of air pollutants 2, 3. Stratospheric ozone (O3) absorbs a part of the sun’s noxious ultraviolet rays, restricting it from reaching the earth’s area 4, 5. By the way, ozone in troposphere is a poisonous air pollutant found in near the earth’s surroundings 6. There are important deals of evidence to demonstrate that ozone in any urban area can harm lung function and hurt the respiratory tract. Ozone exposures can cause heart diseases, premature death, asthmatic attack and bronchitis 7. On the other hand, sulfur dioxide and nitrogen dioxide are notable gaseous pollutants, emission from industrial processes and natural sources that impacts upon human health 8–10. Therefore, due to the danger of theirs breathing, detection and removal of ozone, sulfur dioxide (SO2) and nitrogen dioxide (NO2) are important 11. Hence, a new adsorbent for gas detection has been strictly needed. For removing air pollutant gases, different methods have been considered 12–15.
In recent years, the low dimensional systems has obtained increasing attentions universal 16. The zero, one or two-dimension systems are low dimensional systems. In particular, different two-dimensional (2D) materials have been reported such as graphene, boron nitride, silicon carbide and aluminum nitride monolayer sheets 17–22. Nanosheet materials had larger ratio of surface area to volume, compared to other nanomaterials. Exclusively, silicon carbide nanosheets (SiCNSs) are extensively attend to be useful in electronic devices because of the thermal conductivity, thermal stability and mechanical strength properties 23–25. SiCNSs have much superior chemical reactivity into external adsorbates compared to graphene 26, 27. So far, these structures have attracted a great deal of consideration. For instance, the adsorption of poisonous gaseous (such as CO2, CO, NO2, NH3) on the graphene have been investigated 28–31. Different scientific studies had demonstrated that silicon carbide nanotubes were good adsorbents for some gas, such as SO2, HCN, CO, NO, HCHO, N2O, CO2, O2 and NO2 32–36. Also, special attentions have been given to the properties of metal doped 2D materials 37, 38.
In this work, we have used density functional theory to study the parameters such as adsorption energy, density of states (DOS) analysis, charge analysis and band gap of ozone, sulfur dioxide and nitrogen dioxide molecules adsorption on the pure and Fe-SiCNSs.

2. Computational details
The adsorption of O3, SO2 and NO2 molecules on the surface of pure and Fe-SiCNS are performed by density functional theory (DFT) calculations which were carried out using the DMol3 package in materials studio software 39, 40. The long-range van der Waals interactions (vdW) are considered using Grimme?s method for calculating the energies of the systems with the dispersion correction 41, 42. The spin unrestricted calculations are based on the generalized-gradient approximation (GGA) with the Perdew_Burke_Ernzerhof (PBE) functional to describe all electronic energy of exchange correlation effects 43. The density functional semi-core pseudopotentials (DSPP) and a double numerical plus polarization functions basis sets (DNP) with global orbital cutoff radius of 4.6 Å are adopted. In this calculation, a smearing of 0.01 Ha (1 Ha = 27.212 eV) is used to the orbital occupation. A k-point mesh of at least (8×8×1) points is employed to sample the Brillouin zone by Monkhorst–Pack scheme for the calculation of energy and other properties 44. The convergence threshold is set to be 1.0×10-5 Ha in energy, 2.0×10-3 Ha/ Å in force, and 5.0×10-3 Å in displacement. A 5×5 periodic hexagonal silicon carbide supercell containing 72 atoms (36 Si and 36 C atoms) are selected. The sizes of supercells of silicon carbide nanosheets are set to inside a box of 18.73×18.73×20 Å3.
To calculate the adsorption energy (Ead) of the ozone, sulfur dioxide and nitrogen dioxide molecules on the pure and Fe-doped silicon carbide nanosheets, the following equation is described:
E_ad= E_tot-(E_S + E_M) (1)
here E_tot show the total energy of adsorbed molecules on pure or Fe-SiCNSs. The E_S and E_M are the total energies of pure or Fe-SiCNSs and O3, SO2 and NO2 gases, respectively.

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