density functional theory (dft)

 In this research, the electro-optical aspects of Tetra-Hexagonal-Carbon allotrope as a two-dimensional nanostructure under compressive buckling parameter based on density functional theory (DFT) with PBE-GGA full potential approximation method using simulation software and computational codes based on first-principles calculations have been investigated. The analysis of the results obtained from the calculations of the electronic properties of this nanostructure, such as the band gap and density of states (DOS) under buckling change, indicates that the energy band gap of this nanosheet as a direct band gap semiconductor with 1.61 eV, increases slightly under the influence of the compressive buckling factor and then decreases down to 1.11 eV by applying higher compressive buckling factors. The optical properties of this nanosheet have smooth and regular changes in the out-of-plane polarization, by applying compressive buckling conditions in the visible light spectrum. Also, according to the obtained results, an acceptable match between the electronic and optical properties of this two-dimensional nanostructure is observed, which indicates the correspondence of electronic and optical behaviors, which can predict this carbon nanosheet is a suitable material for designing electro-optical devices.

In this paper, electronic and structural properties such as lattice constant, energy band structure, and density of states of InP in bulk and nanowire are calculated. The calculations have been performed using the Pseudopotential method in the framework of density functional theory (DFT) with local density approximation (LDA), and generalized gradient approximation (GGA) by Quantum Espresso package. The results show a direct bandgap of 1.4 eV at the Γ point in the Brillouin zone and have not cut the Fermi level, with a good agreement with the available experimental results. Also, band structure in nanowires of about 1.49 eV was calculated, which shows an increased bulk state. The calculated results show good agreement with the available experimental results.

first principles calculation, we investigate electronic and optical properties of graphene with B, N, O and F adsorption. For the adatom studied the distortion of the graphene layer is quite significant and cause to change hybridization from sp2 to sp3 also we found that B, F and O adsorptions are n-type, p-type and direct semiconductor respectively while N adsorption has a metal behavior. N absorbed graphene show magnetic moment, while B, O and F absorbed graphene exhibit no magnetic moment. The absorption spectrum of monolayer graphene have been calculated for the cases of in plane (E⊥c), out of plane (E‖c) polarization of light and 45° to the plane of graphene layer and compared with atom adsorption on graphene and it was observed that For the case of (E⊥c) the graphene is an optical sensor for finding F atom and in the case of (E‖c) it is an optical sensor to find B atom in environment.

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. In this study, the electronic structures and optical properties of MXenes M2CF2 (M=Y, Lu) have been investigated using density functional theory (DFT) calculations. Based on the results, the Y2CF2 (Lu2CF2) monolayer is a semiconductor with indirect bandgap of 1.67 eV (1.42eV). Comparing the electronic bandgap of Y2CF2 and Y2CCl2 demonstrates the dependency of electronic and optical properties of these materials to the surface termination taking place during the experimental preparation of MXenes. To study the optical properties, the real and imaginary parts of the dielectric function was calculated. According to the results, there is a remarkable absorption in the ultraviolet and visible regions that they have better absorption compared to that of BP, MoS2 and Sc2CO2 monolayer compositions in the visible region. We have also considered electron energy loss function, refractive index and optical conductivity of the structures. All obtained results express that M2CF2 (M=Y, Lu) monolayers are good candidates for electronic, optoelectronic and solar energy applications.

In this study, the structural, electronic and transport properties of the (5, 0) zig-zag BN, GaAs, GaN, GaP, InN and InP nanotubes have been studied using Density Functional Theory (DFT) combined with Non-Equilibrium Green’s Function (NEGF) formalism with SIESTA software. The electronic band structure, density of states (DOS), current-voltage (I-V) characteristics and quantum conductance curves (dI/dV) of these structures were studied under low-bias conditions. The obtained results demonstrate that all of these structures exhibit semiconducting behavior but the (5, 0) zig-zag GaP nanotube has an indirect band gap which makes it suitable to use for full color displays. Instead the (5, 0) zig-zag GaAs nanotube has a smaller band gap, the highest value of the electron density of states and it showed the amazing property of Negative Differential Resistance (NDR). Therefore, it is an important candidate to use in high-speed optoelectronic devices, high-speed switching devices and high frequency oscillators.

The present study is an applied-developmental study that investigates the increase in efficiency and improvement of the properties of single-walled boron nitride nanotubes (6,6) as nanocarriers for dacarbazine. In this research, the loading of dacarbazine on boron nitride nanotube (6,6) was investigated theoretically and the electron delocalization effects, electrostatic interaction, steric repulsion effects on the structural, electronic properties, and reactivity of dacarbazine on the boron nitride nanotube substrate were studied using quantum mechanical calculations of DFT (Density Functional Theory) evaluated at the B3LYP/6-31G* level of theory. The molecular orbitals distribution was investigated to understand changes in the electronic structures, adsorption energies (Ead), and electrical conductivity during the adsorption process. Frequency calculations were performed to determine the thermodynamic functions and vibrational frequencies in the gas phase. NBO (Natural Bond Orbital analysis) analysis was used to calculate the electronic transition effects as well as electrostatic interactions and other properties of the studied systems. The role of structural parameters, electron transfers, donor-acceptor orbital energies, orbital populations, and NBO charges on the boron nitride nanotube in interaction with dacarbazine were discussed. To determine the electrical conductivity and chemical properties of boron nitride nanotubes reacting by dacarbazine, electron energies, the dipolar moment was calculated and investigated.