نشریه پژوهش سیستم های بس ذره ای
سال یازدهم شماره 2 (پیاپی 29، تابستان 1400)

Recently a new type of two-dimensional material called borophene (boron Sheet) has been successfully synthesized on substrates under very high vacuum conditions and has received much attention. In this paper, using the density functional theory and FP-LAPW + lo method using the GGA approximation, we investigated the electronic and optical properties of borophene with the cmmm space group. The study shows the electronic properties of metallic behavior for this two-dimensional structure. The optical properties also indicate the optical anisotropy of this compound for both x and z directions. Borophene also has a good absorption coefficient in the visible region along the x-ray axis and that the refractive index in this region is less than one.

Among radioisotopes, the technetium isotopes have a special place because of the variety of kits they are labeled with. Recent advances in the field of chemotherapy for radioimmunoassay and the development of technology for PET imaging in the diagnosis of cardiovascular diseases a great attention has been imposed on 94mTc( Iβ+ =72%; Eβ+=2.47 MeV; T1/2 = 52.5 min) as a positron emitter radioisotope of technetium. In this research employing natural molybdenum target has been measured excitation function of natMo(p,n) 94mTc using stacked foils method for 6.4 MeV to 17.4 MeV rang of proton energy and then the excitation function 94Mo (p, n) 94mTc was determined in this energy range. The energy of protons on each of the target stack foils was determined using SRIM software. The cross section for this interaction varied from 21 to 511 mb. The comparison of measured value of excitation function of 94Mo(p,n) 94mTc in this research with the results of two other research groups employing enrichment targets shows reasonable agreement

In this article, a set of 2D numerical simulations were performed for different stages of a real Czochralski (Cz) growth of germanium crystal using Finite Element Method. The results of temperature distribution, melt and gas flow field, and crystal-melt interface were obtained numerically using the Reynolds-averaged turbulence modelling approach. The obtained results show that, as the crystal length is increased (i.e., the melt depth is decreased), the constant rotation rates of crystal and crucible increase both the melt Reynolds number and its turbulent kinetic energy, because of transferring constant momentum and energy to the remaining Ge melt. In addition, the computed crystal-melt interface shape for germanium crystal having 9 cm height was in a good agreement with the experimental data and observations in the crystal growth lab.

Employment of toxic organic compounds such as toluene and xylene in combination with NE-213 scintillator materials make it quite toxic and carcinogenic. They are also volatile and easily leak from the detector cells; therefore working with them is limited and risky. UGLLT and UGAB consist of a less hazard organic solvent and other scintillator combinations and surfactants that have high efficiency for alpha and beta detection. In this research, with aim to develop usage of these scintillators, UGLLT and UGAB new generation scintillators were selected as a safe and inexpensive superseding. The main solvent scintillation, DIN:C16H20 is a low toxic material, with low vapor pressure and high flash temperature. It is well known for biodegradation, maintenance and harmless transportation. These scintillators have been tested for neutron & gamma detection by 241Am-Be, 137Cs & 22Na sources and compared with NE-213. Neutron-gamma discrimination was done by using zero cross method for three scintillators and calculated some parameters such as: figure of merit and peak to valley. The value of FOM in bias: 170KeVee were obtained 1.52 and 1.18 and 1.04 for NE-213, UGLLT and UGAB respectively.

Ratio of level densities with opposite parities in 74Ge with considering the soft phase transition around critical temperatureIn this study , the ratio of nuclear level densities with opposite parities was studied for 74Ge using the generalized, superfluid theory in many - body systems with considering a soft phase transition around the critical temperature. With modified gap parameter, the ratio of nuclear level densities in the form of a smooth function tends to unity with increasing energy . Phase transition occurs at T ≈ 1.1 MeV and at higher energies the approximation of equal parity distribution is applicable .

In this article using a modified Drude model, which includes all dominant electron energy scattering mechanisms and interparticle interactions, the relativistic dynamics of a linear chain of spherical nanoparticle interacting with a laser beam propagating parallel to the orientation of nanoparticles array is investigated. In the point-dipole description of nanoparticles, taking into account interaction of two nearest neighbors, analytical solutions are obtained for the momentum equations of conducting electrons of nanoparticles related to the first, second and third harmonics of laser fields. Formulae are simplified for some asymptotic cases. Numerical analysis is carried out for a linear chain including 10 of 10nm radius Au nanoparticles. It is shown that the interparticle separation has a key role in the nonlinear dynamics of the system. Dipole-dipole interaction of nanoparticles causes a blueshift for the main and third harmonics plasmon resonance, whereas it leads to a redshift for the plasmon resonance of the second order longitudinal displacements of nanoparticles. Related to the different orders, linear and nonlinear polarization of each particle is obtained and permittivity, first and second order susceptibility, linear and nonlinear refractive index of each nanoparticle are analytically obtained which these findings can have direct application in nano-optics and nano-plasmonics.

In this work, the efficacy of fusion cross sections and barrier distributions of 6Li+144,152Sm and 7Li+144,152Sm reactions, as well as the large-angle partial quasi-elastic scattering excitation function and the corresponding barrier distribution for the 6,7Li+144Sm reactions in coupled channel calculation with optical model potential were studied. The results showed that the role of potential and the effect of projectile deformation in these calculations are important parameters. Investigation show that for 6Li+144Sm reaction CDCC calculation has a good agreement with experimental data and for 7Li+144Sm reaction, CCFULL calculation has a good agreement. Forasmuch as the best way to study the behavior of fusion cross section at low energies is the astrophysical S(E) factor, this quantity was used to predict the behavior of 6,7Li+144Sm and 6,7Li+152Sm reactions in energy intervals that the experiment could not be measured. This result predicts the value of energy that the astrophysical S(E) factor had a maximum value, and find the value of S- factor for 6,7Li+144Sm, 6,7Li+152Sm reactions at zero energy by the extrapolation method.

The Kerr-like medium is a beneficial way to obtain the nonclassicality features of a quantum state of light. Moreover, squeezed states are well-known as the best nonclassical ones. Hence, by applying a two-photon parametric process as well as a Kerr medium, squeezed Kerr states can be generated to improve the nonclassicality aspects of Kerr states. In this paper, excited squeezed Kerr states are introduced in which the excitation is normally expressed via bosonic creation operator. Afterward, some physical properties of the introduced states are numerically studied. It is seen that with the help of excitation, the photon statistics of the radiation field can be changed from Poissonian statistics to sub-Poissonian one. Furthermore, adding photons to the considered quantum states remarkably enhances the depth and the domain of quadrature squeezing.

Silver nanoparticles are important in technological and medical applications. The geometricaltuning of the magneto-optical property of these nanoparticles are interesting. As a result oflocalized surface plasmon resonance of these nanoparticle in the visible and near infrared, alarge circular dichroism is appeared close to surface plasmon resonance. In this paper, thecircular dichroism of oblate and prolate spheroidal nanoparticles in the presence of staticmagnetic field is studied. A large redshift is observed in the circular dichroism spectrum of thedimer of oblate spheroids. Also, the magnitude of circular dichroism in an asymmetricconfiguration of the dimer is observed in comparison to the circular dichroism of the dimer ofsame volume spherical nanoparticles, which shows the measurements are very easier.

In this study, the density of states, heat capacity, and magnetic susceptibility of carbon nanodiscs and nanowires with different diameters are calculated via the tight-binding approximation and the Green’s function approach. The results indicate that by increasing the diameter, the nanodiscs move from a semi-conductive and tend toward a semi-metal which is in agreement with other theoretical works. Also, increasing the diameter of the nanowires causes them to exhibit a metallic behavior. It is observed that increasing the diameter of these nanostructures increases the number of the Van Hove singularities in the density of states diagrams. A Schottky anomaly peak is seen in the heat capacity curves of these two nanostructures, which for the nanodisc/nanowire with the largest diameter, has a lower height. Due to the presence of the Van Hove singularities in the density of states diagram, a crossover is seen in the magnetic susceptibility curves, which splits these diagrams into two high temperature and low temperature regions. It is also concluded that at low temperatures, increase in the diameter of the nanodiscs and nanowires increases the magnetic susceptibility. These maximum values are also observed in the heat capacity and magnetic susceptibility curves of other graphene and graphene-like nanostructures.

In this paper, we study a system consisting of two two-level atoms under XXX and XYZ Heisenberg interaction coupled with optical cavity. Calculating Hamiltonian of two-qubit Heisenberg interaction in the presence of electromagnetic field in Jaynes-Cummings model, we obtain the density matrix of the system by Gibbs equation in the thermal equilibrium. Assuming an arbitrary pure state as input state in the quantum channel, we obtain the output state for the system under the thermal equilibrium. The result of our study shows, as the temperature increases as the entanglement decreases until it reaches to zero and the fidelity decreases until it reaches to a steady amount. Also, we have found that the assumed model is a suitable system for transmitting quantum information with high efficiency..

In this study, we investigate the electronic and thermoelectric properties of monolayer nanostructures of C2B4 and C4B2 by first principles calculations. At the first, we calculated the electronic band structure and density of states based on density functional theory (DFT) and using the QUANTUM ESPRESSO computational package. The band gap values were obtained as 0.43 eV (direct band) and 1.45 eV (indirect band) for C4B2 and C2B4, respectively. Then, based on the calculated electronic energy, we obtain the thermoelectric transport coefficients such as the Seebeck coefficient, electrical conductivity, electrical thermal conductivity, and dimensionless figure of merit by solving the semiclassical Boltzmann transport equation in relaxation time approximation and within Boltztrap computational package. The calculated results show almost isotropic transport properties for both nanostructures. In particular, the C2B4 nanostructure exhibit comparative thermoelectric performance compared to C4B2. Also, the Seebeck coefficient and figure of merit of C2B4 is even larger than that of C4B2 under the studied carrier concentration and temperature region, so that, the Seebeck coefficient and figure of merit for p-type doping at room temperature were obtained as 1765 µV/K and 1.02 for C2B4, and 216 µV/K and 0.81 for C4B2, respectively.