JOURNAL OF RESEARCH ON MANY BODY SYSTEMS
Year:2019 | Volume:9 | Issue:1|Papers Count:21

In this article, bismuth ferrite nanoparticles (BiFeO3) were prepared by sol-gel method. To determine the sintering temperature range of bismuth ferrite nanoparticles, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were performed on its dry gel. In order to improve structural and optical properties, samples sintered at temperatures of 600‚ 650, 700, 750, 800 and 850 ° C. Then‚ structural and optical properties of the samples have been investigated of by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FESEM), Ultraviolet-visible spectroscopy analysis (UV-Vis) and Photoluminescence analysis (PL). The result of XRD and FT-IR analysis showed that samples have distorted perovskite structure. FESEM images indicated that by increasing sintering temperature, the size of nanoparticles increases. UV-Vis and PL analysis showed that samples are semiconductor and have an energy gap of about 2 (ev).

In the multipartite systems there exist different types of entanglement where genuine entanglement is an important one. Due to its importance in quantum information tasks, various criteria have been presented for the detection of genuine entanglement. One of them is the criterion introduced by Shchukin et al. [E. Shchukin and P. van Loock, Phys. Rev. A 92, 042328 (2015)]. First they established an inequality such that any multipartite continuous-variable quantum state violating the inequality for any bipartition is genuine entangled. Since application of the inequality requires numerical optimization and becomes more difficult by increasing the number of parties, next by using the inequality they presented a single analytical condition for genuine entanglement which, although is not the best possible one, does not have these difficulties. In this paper, using the original inequality, we present a single analytical condition for genuine entanglement whose lower bound is greater than the lower bound of the analytical condition obtained by them and so it is able to detect more genuine entangled states. Moreover, it has the same detection ability as the original inequality without having its difficulties. We illustrate this through an example.

The nonlinear propagation of electromagnetic waves in a plasma Bragg grating is considered. In a weakly relativistic regime, by means of the Maxwell’ s equations along with a plasma fluid model, two coupled equations are found that govern the evolution of the envelopes of forward and backward propagating waves in a cold unmagnetized plasma undergoing an ambient density modulation in the form of gratings. Then, the nonlinear plane wave solutions with constant amplitude are obtained and the stability of them against a small perturbation is investigated. The dependence of the growth rate and instability window on relevant parameters of the system is addressed.

The electronic, band offset and magnetic properties of Mn2FeAl /GaAs are investigated by first-principles calculations using density functional theory with generalized gradiant approgximation (GGA). The Mn-Mn/Ga interface is stable in terms of energy. The simultaneous analysis of the shotkey barriers and the electrostatic potential for this structure indicates the type III band alignment, where the valence band edge of Mn2FeAl is higher than that of conduction band edge of Gallium arsenide. We find a valence band offset (VBO) of 1. 54eV and conduction band offset(CBO) of 1. 39eV. Hence, Mn2FeAl /GaAs (001) is recommended for GMR and TMR applications. There was an electrostatic potential difference of 0. 056 μ V and also half-metallic behavior in this interface.

In this paper, we calculated the electronic properties of graphene in the presence and absence of the gold and nickelatoms using the density functional theory. The electronic structure, density of states, stability, band gap and spin polarization are studied. Our calculation is performed with SIESTA software. For this reason, we used local density approximation (LDA) and generalized gradient approximation (GGA) to calculate the exchange-correlation potential. The results show that the stability and spin polarization increase while the band gap decrease when the size of graphene increases. Graphene layer doesn’ t have any spin polarization but in the presence of impurity, it shows the spin polarization depends on the gold and nickel impurities location. Also gold and nickel impurities defer the flatness of surface. The is hybridization between H(s) with C(p) ingraphene with impurities of gold and nickeland hybridization between Au(d) and Ni(d) with C(p) orbitals.

The thin films of N: ZnO are deposited on the glass substrate by the DC magnetron sputtering in 10-2 Torr pressure in equal amount of Ar and N2 as sputtering gas. Thickness, morphology, crystalline structure and optical properties of layers were detected in three different sputtering time depositions. By increasing the time deposition, the thickness of the layers, the roughness of the surfaces and the height of the grains increase. The hexagonal (wurtzite) N: ZnO structure layers have grown with high (002) textured structure. In the N: ZnO, the lattice parameter, c, increases compare to pure ZnO. These layers have an optical gap about 3. 2 eV which increased with thickness increasing this result was confirmed by photoluminescence spectra. The Raman spectrum confirmed the XRD results and the doping of nitrogen into the crystal structure of zinc oxide. The thickness of the layers was calculated by the Swanepoel method, which was close to the thickness measurement.

In this research spontaneous fission of 284Fl superheavy nucleus has been studied using Coulomb and nuclear proximity potential. Released energy in each fragmentation Q, driving potential (V-Q), penetrability, decay constant and fission yield for each individual fragmentation are calculated. With respect to the mass and charge asymmetry, the most favorable fragmentation in the binary spontaneous fission occurs for the highest Q value and the lowest driving potential (V-Q). For spontaneous fission of 284Fl superheavy nucleus, the highest yield has been seen for 136Xe isotope (N = 82, Z = 54) as one of the Fragments. The comparison between relative yields shows the role of doubly magic and near doubly magic nuclei in having the highest fission yield. The spontaneous fission half-life of 284Fl superheavy nucleus are calculated by obtaining the total decay constant λ and compared with the results of semi empirical formula as well as experimental data. Satisfactory agreement achieved between the results of this approach and experimental data than the results of semi empirical formulas

Using first-principles electronic structure calculations based on density functional theory, the electronic, magnetic, and structural properties of novel d0-d half-Heusler compounds XYBi (X=K, Rb; Y =Sc, Ti, V, Cr) are investigated. The results indicate that 6 of these compounds, namely, KTiBi, RbTiBi, KVBi, RbVBi, KCrBi and RbCrBi are half-metallic ferromagnets. The half-metallic energy band-gap of these compounds were calculated in the range of 0. 46-0. 71 eV. A detailed study of the partial density of states showed that the p-d exchange between transition metals 3d and Bi 6p states is mainly responsible for the half-metallic behavior. The total magnetic moments of the compounds under study are in agreement with the Slater-Pauling rule Mtot=Ztot-8 and it is integer valued in a wide range around the equilibrium lattice constant, which indicates that the half-metallic property is not sensitive to the lattice parameter. Employing the structure optimization program USPEX, it is shown that the introduction of d0 alkali metal atom leads to structural stability of the above novel half-Heusler compounds. In the light of their structural stability, high Curie temperature and large half-metallic gap, the above compounds are good candidates for spintronic applications.

One of the most challenging and exciting goals of modern physics is to achieve good and quantitative understanding of the strong interaction. Significant progress is achieved in recent years, all thanks to the remarkable progress in the study of empirical and speculative. Tentatively, study about hadron structure can be done by electrons, pions, kaons, protons and antiprotons. Antiprotons are excellent tools to inspect the antiprotons-protons annihilation problems, a particle with gluonic degrees of freedom and particle and antiparticle pair which are produced repeatedly, and also allow spectroscopy studying with very high precision and statistics. In order to identify more such as these cases, P ̅ ANDA experiment is designed to be completely extraordinary physical potential due to exploit the availability of cold and high-intensity beams of antiprotons. So, for more understanding and study of high-energy physics and strong interactions, P ̅ ANDA experiment is designed. One of the significant parts of the P ̅ ANDA set-up is gas electron multiplayer tracking systems which are under studying and construction. In this article is tried to demonstrate the influence of one typical kind of these systems in order to improve precise particles mass measurement, tracking efficiency and momentum resolution.

In this investigation, the approximate solution of Schrodinger equation with mean field Woods-Saxon potential in harmonic oscillator basis has been given. The eigen value energy and corresponding eigen function of bound single particle neutron and proton energy levels for some light, medium weight, and heavy nuclei were determined. Obtained results were compared with numerical solution of Schrodinger equation and good agreements were observed between two methods. By using Nikiforov-Uvarov (NU) method and considering boundary conditions the analytics and accurate solution of Schrodinger equation with Woods-Saxon potential have been represented for S-state neutron single particle. The energy levels for some light, medium weight, and heavy nuclei were calculated. Obtained results showed that the value of energy levels is strictly dependent to the adjustable parameters of Woods-Saxon potential and method of calculation. Such that by increase of atomic number and principle quantum number the discrepancy between calculated data by using numerical solution and analytic solution with different set of adjustable parameters is increased.

Nowadays, electron sources based on field emitters have an important role in our life. For example, utilizing the field emitters in electron microscopes, field emission displays, and solar cells are the main application of the field emission. In recent years carbon naotubes (CNTs) have been considered as a good electron emitter because of their unique electron conductivity. Also, TiO2 nanotubes as a metal oxide semiconductor with capability to grow on a conductive substrate can be a promising candidate for electron emitter. In this study, we have focused on investigating the field emission characteristics of the bare TiO2 nanotubes and CNT coated TiO2 nanotubes to achieve a high current electron emitter. In this study, we have shown that the layered nanostructures have a significantly higher electron emission comparing to the bare TiO2 nanotubes. Also, the emission current from these nanostructures changes udder the light exposure.

In this research, magnesium ferrite nanostructures have been prepared by the ultrasound-assisted method and for their structural, optical and magnetic characteristics, different methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible spectroscopy and vibrating sampling magnetometer (VSM), have been used. XRD pattern of the prepared magnesium ferrite nanostructures shows mixed cubic spinel phase. SEM images show a nearly spherical form of nanostructures and the mean nanoparticles size are about 10-15nm. Bandgap value of the prepared magnesium ferrite derived from UV-visible absorption spectra is 2. 8eVwhich in comparison with its bulk value, a blue shift (0. 62eV) due to the quantum confinement effect observed. The hysteresis loop of the prepared sample from the VSM analysis for the prepared magnesium ferrite nanostructures at room temperature shows a paramagnetic behavior. The optimum value of the pH of MB was 13. The intensity and spectrum of light source were engineered and the most efficient state has been used for the experiment. the results showed that within 45 minutes 99% of dye is degraded by magnesium ferrite nanostructures.

In this article, a transparent gallium doped zinc oxide nanocomposite with a novel photoluminescence properties was prepared at room temperature. GZO nanocrystals were synthesized by the simple sol-gel method. The optical, structural and morphological properties of the samples were investigated by various analysis including photoluminescence spectrum, absorption spectrum, XRD, EDAX, FTIR, TEM and FESEM images. The XRD study showed that the samples had a wurtzite structure consistent with all crystalline plates of ZnO without any additional peaks or oxidation phases. Two nanocomposites containing dried nanopowders and the other containing calcined nanopowders were also prepared. Calcined nanocomposite exhibited good optical properties, including 70% optical transparency in the visible wavelength region with a high green emission peak at the room temperature. Also, the presence of gallium and zinc and related bonds in the structure was confirmed by EDAX and FTIR characterization. Studies have shown that the GZO composite has a novel luminance property in the blue-to-green visible region, which can be a good candidate for photo detection and photonic applications with a very low cost.

In liquid crystals, pear-shaped and banana molecules find a splay and bend arrangements, due to their asymmetry. In these crystals, the director deviation from equilibrium produces pure polarization. This effect is called Flexoelectricity. Flexoelectric coefficients in liquid crystals were derived from simulation and experimental methods. In density functional theory, these coefficients depend on the direct correlation and the angular distribution functions of molecules. In this work, by using parameterized hard Gaussian overlap method the closest distance of hard pear shape molecules is calculated. By using this closest distance, the approximate direct correlation function of pear-shaped molecules is obtained. Using this correlation function and deduced proper distribution function, the dipolar Flexoelectric coefficients for liquid crystals with elongations 3 and 5 pear-shaped molecules are calculated. The results are consistent with the simulation results qualitatively.

Within the semi-classical approximation of Thomas-Fermi, which is based on a statistical approach, the phase-space occupation equation number of nuclear matter is obtained by employing the Landau Fermi-Liquid theory. At the first, using the NN-interactions of Myers and Swiatecki, known as TF(96) and TF(90), the equation of state of nuclear matter (EOS) is derived. Then, a special attention is devoted to studying the behavior of symmetry energy and symmetry free energy quantities which have a substantial effect on the equation of state. Hence, the stiffer behavior of the EOS in the TF(90) interaction compared to the TF(96) interaction, refers to the important effects of these quantities. The extensibility feature of the present model is shown by determining the saturation density and the saturation incompressibility coefficient. In addition to the comparison of symmetry energy, symmetry free energy and incompressibility coefficient with the results of other models, the temperature effects on these quantities are also studied.

With the growth of science and technology and according to the vision of human knowledge, it is predictable that hydrogen will be the future fuel of human society. Chemical decomposition of water for fuel production through direct conversion of solar energy has been proposed as an interesting topic in science. In this experimental work, BiVO4 films as a photoanode were prepared by spray pyrolysis deposition method. Cobalt oxide was used as a cocatalyst and deposited on BiVO4 films by spin coating method. Five samples were calcined at 400oC for 1-5 hours to study the effect of calcination time on the morphology of BiVO4 films. Results showed that by increasing calcination time, the photo-current rises. This is because that by increasing calcination time, atoms were able to move into low energy sites at the surface and so separated individual nanoparticles could attach together to make better connectivity to the substrate. The XRD patterns also showed that there are no critical changes in the microstructure of the layers. The UV-VIS spectrum of samples shows an increase in photo absorption which is related to the variation in grain size of BiVO4 films.

In heavy ion fusion is one of the ways of producing nuclear energy, target is directly compressed by heavy ion beams. Ion beam due to high efficiency, repetition rate and high performance capability are more advantages than lasers. The design of pulse shape and target layers are important parameters in gain value. In this paper, the target hydrodynamic parameters driven by bismuth ion beam with energy 10GeV and pulse duration 21ns, are simulated with the finite difference time domain) FDTD) method. The calculated gain is 222 for a typical fuel pellet. The gain calculated for a desired target is achieved 222. Our simulation results are compared with the results of MEDUSA and DEIRA codes.

In this study, we investigate the spin polarized current in a zigzag hexagonal phosphorene quantum dot composed of and phosphorus atoms using Green's function method. Supposing that all input electrons have spin-up orientation, we have shown that an output current with desirable spin polarization may be achieved by applying an appropriate external electric field controlled by a gate voltage. Particularly, there are conditions where the spin of all electrons can be inverted; therefore, the system can act as a spin inverter that has special applications in spintronics and quantum computations. Moreover, it is demonstrated that increasing the size of phosphorene quantum dot leads to the increase of polarized current.

In this paper, the first principle study of the electronic and optical properties of new monolayer penta-(C4B2, C2B4, and C2N4) via the density functional theory (DFT) and using the Wien2k code are studied. Our results demonstrate that the monolayer penta-(C4B2, C2B4, and C2N4) are semiconductors with gap energies 0. 2 eV, 1. 2 eV, and 3. 1 eV, respectively. Also, in the optical properties section, a number of optical parameters optical virtues such as reflectivity, dielectric function, and energy loss function versus energy variations are calculated. The results of the optical calculations show that, in the x-polarization of the electric field, the optical band gap corresponds to the electronic band gap, and the plasmon energy matches with the free electron model. Also, the effective number of electrons in an energy of about 15 eV was found to be equivalent to 21, 20, and 20 electrons, respectively, which is small compared to the free electron, due to the localization of the number of electrons.

In this paper, we investigate quantum renormalization group theory in transverse Ising model on one dimensional chain of spin-1/2 particles. To this end, we employ recursion relations to quantum renormalization of coherence measure at ground state. Coherence measure diagram in terms of intensity of transverse field for higher renormalization steps shows the detection of quantum phase transition point for transverse Ising model which implies that the coherence measure can be a good indicator of quantum phase transition in transverse Ising model. Also, we obtain the divergence behavior that governs the first derivative of the coherence measure behavior, near to critical point. Although the coherence measure depends on the basis of writing the density matrix, results show that the quantum phase transition point detected by coherence measure is independent of selected basis.