چكيده به لاتين
As a new family of 2D materials, transition metal carbides and nitrides (MXenes) have attracted growing attention in recent years due to their widespread potential applications. The introduction of nanoscale materials, 2D materials, the synthesis, and the introduction of optical quantities have been discussed in chapter one of this thesis. The main fields of theory, computational method, and software (Quantum ESPERSSO) were examined in chapter two. The third chapter discussed MXenes introduction, synthesis method, properties, and applications. Also, all DFT calculations for geometrical optimizations, electronic structures, and evaluation of optical properties by the code (QE), which is in the form of density functional theory and quasi-potential method, were examined using plane waves as a basis in the fourth chapter. Using the GGA approximation, calculations were performed. The band structure and density of states have been evaluated for electronic structural investigation. Refractive index, absorption coefficient, optical transmission, dielectric function, energy loss function, and reflectivity were investigated to check optical properties. These four monolayers' density of states graph shows that the C-2P, O-2P, and S-4d orbitals play the largest roles in the VBM and CBM parts. The results obtained from the electronic band structure showed that the bandgaps of 2D semiconductors Sc2CCl2, Sc2CF2, Sc2CO2, and Sc2(OH)2 are, respectively, 0.90 indirect, 1.05 indirect, 1.53 direct, and 0.21 direct electron volts. According to the results from the optical properties of the real part of the dielectric function for the 2D Sc2CCl2, Sc2CF2, Sc2CO2, and Sc2C(OH)2 monolayers in the x(z) direction, respectively, 2(1), 1(0), 1(0), and 2(1) peaks have been observed in the range of visible spectrum. For the 2D Sc2CCl2, Sc2CF2, Sc2CO2, and Sc2C(OH)2 monolayers, the imaginary part of the dielectric function shows 1(1), 1(0), 0(0), and 2(1) peaks in the visible spectrum, respectively, in the direction of x(z). The intensity of the peaks of the 2D Sc2CCl2 monolayer is higher compared to that of the 2D Sc2C(OH)2, Sc2CF2, and Sc2CO2 monolayers, based on the absorption results obtained along the x(z) direction. According to a previous study on 2D materials such blue phosphorus, MoS2, AlN, and ReT2 (T=S, Se), 2D Sc2CCl2, Sc2C(OH)2, Sc2CF2, and Sc2CO2 monolayers have better absorption than these 2D materials. The highest peaks in the reflection results of these monolayers in the ultraviolet region indicate the maximum reflection; in this case, we will observe a decrease in the absorption and transmission of electromagnetic waves. These four 2D monolayers therefore have the potential to be used in UV protection applications and as reflective layers in solar cells considering the electronic and optical properties.
