نشریه پژوهش سیستم های بس ذره ای
سال یازدهم شماره 1 (پیاپی 28، بهار 1400)

In this paper, the electronic transport properties of graphene-like borophene as well as its doped structures with boron, carbon and nitrogen atoms are investigated using the density functional theory. Total and partial density of states, band structure, charge density, quantum conductance and current-voltage characteristic of these structures have been studied and compared. The results indicate that graphene-like borophene is a metal, and has a Dirac point with a linear dispersion relation similar graphene. Our investigations demonstrate that the Dirac point is in upper place than the Fermi level, and the doping can affect the location of Dirac point. Moreover, the current-voltage characteristics show Ohmic behavior of these structures. In doped graphene-like borophene structures, boron atoms are formed ionic bonds. In all considered structures, the current density along zigzag and armchair directions exhibit an anisotropic behavior. By 90° rotation of graphene-like borophene sheet with carbon atom, its current is controlled and this material can be used to design nanoelectronic switches. The current control with C atom doping can be used in this two-dimensional material to design nanoelectronic switches.

In this study, pure bismuth oxide (Bi2O3) nanostructures and bismuth oxide- molybdenum bismuth oxide (Bi2O3/ Bi2MoO6) nanocomposites with additive 2, 4, 6, 8, 10 and 12cc values of molybdenum precursor (Na2MoO4.2H2O) were prepared by ultrasound assisted-method, and the effect of additive values of molybdenum precursor has been studied on the photocatalytic activity of pure bismuth oxide nanostructures by removing methylene blue from the water. The structural, morphological and optical properties of these nanostructures have been investigated by TGA/DTA, XRD, SEM and UV-Vis analyzes. The results of XRD show that with increasing of additive values of molybdenum precursor, the intensity of bismuth oxide diffraction peaks decreases and the intensity of bismuth oxide molybdenum diffraction peaks becomes more apparent. SEM images show change in the nanocomposite’s morphology and their size due to additive of molybdenum precursor. The energy gap of nanocomposites was calculated by UV-Vis spectrum, and the results showed that, the energy gap of the samples has been reduced with increasing the amount of molybdenum precursor. Also, the results of photocatalytic activity showed that the nanocomposite containing 2cc molybdenum precursor has the highest photocatalytic activity among the prepared samples and removed 100% methylene blue from the water within 24 minutes.

In this paper, the effects of structural parameters and temperature on the thermal emission properties of a square array of cylindrical nano/microcavities on chromium (Cr) slab have been investigated. The obtained results show that the enhancement and selectivity in the emissivity are depended on the coupling between thermally excited radiation with the resonance modes, surface plasmon-polariton and Bragg diffraction from the surface of the periodic nano/microcavities. For nanocavities with radius r

In this research, squeeze vacuum state of quantum light is simulated. For this purpose, single mode dissipative cavity with non-zero second-order susceptibility is used. Cavity nonlinear medium is driving by laser pump with known frequency, and pairs of identical photons are created, with one-half frequency of driving pump. This process known as degenerate parametric down conversion. In the absence of any dissipation, simulation shows linear time dependent squeezing parameter, which is in agreement with theoretical results. In two photon loss of cavity in contact with cold reservoir, competition between gain and two photon loss, results in stable squeezing of initial vacuum, in steady state of system.

In this article we investigate the effects of particles’ geometry on the uniaxial-biaxial and planar nematic-homeotropic phase transition of hard cylinders and hard rectangular rods between two structureless walls. The calculations are doneusing the Parsons-Lee theory into the Zwanzig approximation. These particles show a first order phase transition from planar to homeotropic that disappears at a critical point for both particles which this critical point is and for hard rectangular and cylinder rods, respectively. In addition, there is a second order phase transition called uniaxial planar nematic to biaxial planar nematicwhere there is three different optical axes for both shapes. This transition occurs at higher densities for the particles with smaller shape anisiorpies due to decreasing of excluded area inplanar order. Our calculations depict that both types of phase transitions take place at lower densities

In this research, we have considered quantum phase transition for even-even neodymium isotopes ( ) using the Hamiltonian of Interacting Boson Model (IBM-1) in the framework of affine SU(1,1) Lie algebra. The energy spectrum of this chain has obtained by calculating the Hamiltonian control parameters with Least Squares method. In the following, energy surfaces using coherent state formalism has calculated. Changes observed in the energy surfaces and the values of showed that the  isotope is the transitional nuclei between U(5) and SO(6) limits. The results of this model are in good agreement with New Empirical Formula (NEF).

In this research, the geometrical parameters, the spin density of atoms, and the EPR parameters of radiation and mechanically induced radicals in alpha keratin were investigated using density functional theory. Generally, various factors such as hydrogen bonds and temperature impact the EPR parameters. First, cluster calculations were used to study the effect of hydrogen bonds, and then ab-initio molecular dynamics calculations were used to investigate the simultaneous effects of hydrogen bonds and temperature. Variation of the g tensor components and the coupling constants are dependent on the change of the geometrical parameters and the spin density of the atoms. Due to being a small variation of the geometrical parameters and the spin density of the atoms between the cluster model and the molecular dynamics for the radiation and the mechanically induced radicals, the difference between calculated EPR parameters by means of two mentioned models is insignificant. The result shows a good agreement between the calculated EPR parameters and the experimental results. Also, due to the considering of the ambient temperature effect, the obtained results from the molecular dynamic calculation have a better agreement with the experimental data in comparison to the cluster model.

Entanglement is one of the fundamental quantum concepts that not only distinguishes quantum mechanics from its classical counterpart but also plays important roles in quantum communication and information processing technologies. Here, we aim to study anisotropy contributions of continuous variable entanglement between magnon modes in antiferromagnets. By introducing different bosonic modes, it is shown that the magnetic uniaxial anisotropy induces different entanglement contributions in the ground state of the system. While some of these contributions appear to be decreasing with respect to anisotropy, the other contributions are increasing as functions of anisotropy. It is also shown that the maximum magnon entanglement is always at the centre of Brillouin zone. The analysis presented here is independent of geometric lattice structure and appropriate for many classes of compounds.

Utilizing boundary element method (BEM), we investigate fluorescence rate enhancement by conical nanoantennas. The nanoantennas consist of two gold nanoparticles located along a line on both sides of the molecule. Molecular fluorescence rate can be considerably enhanced by nanoantennas. The fluorescence rate depends on the orientation, distance and position of molecule with respect to nanoantennas, as well as the effect of the incident light angle and the gap distance of the two nanoparticles. In practice, it is not easy to fix a precise position and orientation for a molecule in the vicinity of a nanoantenna. By allowing for the effect of molecule position and orientation on the emission spectra, one can achieve a better agreement between experimental results and theoretical calculations. Moreover, it provides important information to design the experimental configuration.

In this paper, a new numerical method is introduced to solve the time-dependent nonlinear Schrödinger equation. The proposed method is a combination of a novel metaheuristic optimization algorithm with the finite difference method. First, the regarded Schrödinger equation with the ralated boundary and initial conditions are converted into an unconstrained problem. For this purpose, the boundary and initial conditions are satisfied using the penalty method and a proper objective function is defined through the discretized governing equation. Then, a successful version of the particle swarm optimization is implemented to minimize the identified error function and find the best nodal values. The simulation results for several cases are illustrated to depict the effectiveness and capability of the introduced sterategy for solving the time-dependent nonlinear Schrödinger equation.

In this paper, the hydromagnetic waves are studied in a degenerate complex magnetoplasma environment taking into account the quantum forces related to the electron spin and the quantum potentials of the ions and electrons. To this end, a modified quantum fluid formalism including the quantum density fluctuations and spin magnetization energy is employed to analyze the dispersive properties of the wave modes. The results show that the presence of dust particles as well as quantum corrections significantly alter the behavior of the waves. In other words, the dispersion of waves decreases with the mass of dust particles. Also, the corrections due to the density fluctuations of ions and electrons have significant effects and introduce non-linear terms in the dispersion relation. In addition, the effect of the electron spin reduces the contribution of other quantum potentials on the dispersion of wave modes. Finally, some special limiting cases are discussed.

We investigate the radiative heat transfer in systems of magneto-optical nanoparticles. The resonance of surface modes due to an external magnetic field results in an anisotropic optical response of these nanoparticles. Using the many-body radiative heat transfer theory, we have investigated the influence of the magnitude and the direction of an external magnetic field on the steady state temperature of system of magneto-optical nanoparticles. Moreover, the influence of configuration symmetry breaking (with change of nanoparticles size) on the net heat exchange and temperatures are investigated in a three body system and the results are compared to that of symmetrical system.