مجله فیزیک کاربردی
سال سیزدهم شماره 3 (پیاپی 34، پاییز 1402)

In this paper, we use density functional theory and first-principles calculations to evaluate the structural, dynamic, and thermophysical properties of thorium phosphide. The structural properties including lattice constant (a0), bulk modulus (B0), and first-order derivative of bulk modulus (B0') are calculated by fitting the Brich-Murnaghan third-order equation of state and compared with other experimental data. This comparison shows a satisfactory agreement between the calculated and experimental lattice constants. The phonon dispersion diagram is calculated by the linear response approach along the high symmetry points. The results indicate the absence of negative modes in the phonon spectrum, which shows that the structure is dynamically stable. We observe a good agreement with the comparison of the obtained optical frequency with the experimental data from the inelastic neutron measurement. The analysis of the phonon density of the states diagram shows a phonon gap in the distance from 115 to 262 cm-1 for this material. Thermodynamic properties including Debye temperature, vibrational entropy, isothermal bulk modulus, isochoric heat capacity, thermal expansion, and Grüneisen parameter are evaluated by the quasi-harmonic Debye method at high pressures and temperatures. It is observed that the Debye temperature of thorium phosphide decreases with increasing temperature at a constant pressure and increases with increasing pressure at a constant temperature. The reduction of the Grüneisen parameter due to the application of pressure shows the changes in the phonon frequencies with the changes in the volume of the unit cell. Also, the increase of the Groningen parameter due to the increase in temperature can be the result of changing the dynamics of the network.

In this research, the symmetry of high-order harmonics resulting from the interaction of a single-layer WSe2 with a linearly polarized laser in both zigzag and armchair directions have been investigated using time-dependent density functional theory in real space. The dependence of the cutoff frequency behavior with the increase of the electric field amplitude and the behavior of the harmonic yield with the laser wavelength has been analyzed. The results show the linear dependence of the cutoff frequency with the electric field and the exponential behavior of the harmonic yield with the laser wavelength. Also, the effect of the input laser field polarization on the high-order harmonic spectrum and harmonic yield has been investigated. Changing the rotation angle of laser polarization to 30 degrees for elliptically polarized light with an ellipticity parameter of 0.1 creates the highest harmonic yield. Also, the results of this research show that by changing the polarization of the input electric field, the polarization of high-order harmonics also changes, which leads to the production of high-order harmonics with different polarization.

A hybrid system including a quantum emitter in the vicinity of a plasmonic core-shell nanostructure in the air is considered, and the spontaneous emission process of the emitter is investigated. The aim is to examine the effect of the plasmonic system on the quantum speed limit and the non-Markovian dynamics of the system. Using the dyadic Green's function of the system, the impact of geometric parameters such as the thickness of the plasmonic nanostructure shell and the distance between the emitter and the nanostructure on the evolution and physical behavior of the desired parameters has been investigated. According to the obtained results, by increasing the distance of the emitter from the nanostructure, the dynamics of spontaneous emission change from non-Markovian to Markovian, and the value of the non-Markovian measure tends to zero. In this condition, the quantum speed limit increases and becomes equal to the evolution time of the system. In addition, as the thickness of the shell increases, the mean value of the non-Markovian measure decreases.

In recent years, many studies have been conducted on the use of perovskite materials in solar cells. The process of pouring chlorobenzene affects the crystallinity of perovskite and thus the efficiency of the resulting solar cell. In this study, we found the best time interval to pour chlorobenzene after starting spin coating to obtain crystalline perovskite. After pouring the perovskite precursor on the substrate and starting the rotation, time intervals of 4, 6, 8, 9, and 12 seconds were tested for pouring chlorobenzene. The sample was then heated to form a perovskite layer, in some cases the layer was cloudy, indicating defective perovskite with incomplete crystallinity. Then, other layers, including Spiro-OMeTAD and metal contacts, were added. After reviewing the graphs and studies, it has been determined that the highest efficiency (16.71%) is obtained for the resulting solar cell in a time interval of 8 seconds for pouring chlorobenzene.

In this paper, the behavior of the double pendulums has been studied by considering the effect of initial conditions (angular displacement of the outer pendulum for four cases 12, 30, 90, and 150 degrees) and the influence of system geometry (increasing rod length and mass of the second pendulum), also. After extracting motion equations using the Lagrangian method, in order to deal with the frequency spectrum, traces of bobs, and understanding the system behavior for every case, the Fast Fourier Transform (FFT) technique and Poincare sections have been applied. The obtained results show that the consequence of the rising angular displacement the outer pendulum is to increase the energy level of the system and the change of its behavior from quasi-periodic for angular displacement is less than 90 degrees to chaotic when it is 150 degrees. Therefore, the energy level, in this case, has increased more than twice compared to the first. In addition, it seems a quasi-periodic behavior is forming at the heart of chaotic behavior. On the other hand, the results indicate a very significant effect of geometrics on a system's behavior. According to the calculations, the consequence of increasing the length of the rod of the second pendulum has only led to a different behavior from its similar case (case number 3) completely. however, their energy level is the same. Increasing the mass of the outer by twice not only to lead decrease energy level of the system by 330J but also has shown chaotic behavior (in comparison to the case3).

At the stagnation time, fuel may impact by a variety of paths, including ablator materials, Hohlraum wall, the interaction of the cone-guided lateral surface with imploding fuel, and cone tip material, releasing and mixing their constituent elements into corona plasma and even inside the pure dense fuel. Here, we have parametrically studied the impact of some well-known ionic impurities such as carbon and gold on the physical condition of DT hot spot ignition. The admissible zone of DT hot spot ignition was plotted on the HsTs plane, and it was shown that for a given percentage of gold impurities, the boundaries of the ignition zone gradually increased with increasing internal implosion velocity and at implosion velocities smaller than 1.7×107 cm/s, there exist two individual ignition islands. In the context of the fast ignition approach to ICF, the areal density of hot spots ignition of deuterium-tritium doped with a small concentration of impurity ions of carbon and gold was then extracted by a non-equilibrium ignition model. Accordingly, for a given value in this range, the contour plot of the allowed areal density parameter in the two-temperature model was plotted on the Te-Ti plane. It has been shown that as the impurity fraction increases, the permissible range of ignition decreases rapidly and the ignition conditions become more difficult. The sensitivity of these changes is directly associated with the coefficient of increase in radiation loss power, which is a function of the parameter of the impurity percentage α and the ionization state of the impurity ion, Zimp. Moreover, in each contour plot, the minimum permissible ignition parameter of ion temperature of contaminated DT fuel is also visible.

Alvand tokamak is a small-sized research tokamak for magnetically confined plasma studies. The plasma cross-section of this tokamak is circular, and its simpler structure compared to tokamaks with an elongated cross-section allows for more fundamental physics research. One of the important topics in the stability of tokamak plasma and increasing the confinement time is the study of plasma equilibrium according to the geometry and boundary conditions of the tokamak. In this research, the Grad-Shafranov equilibrium equation for Alvand tokamak geometry was investigated and analyzed numerically. The data obtained from the calculations showed that for a plasma current of about 30 kA and a vertical field coil, a current of 1400 A, the lowest aspect ratio for the plasma cross section is obtained, which will be equal to 4.2. Plasma production with this aspect ratio leads to the presence of plasma in the entire area allowed by the limiters and thus there will be the largest possible volume of plasma in the tokamak chamber.

One of the most critical aspects of studying entanglement states is quantifying the degree of entanglement. One of the entanglement measures for pure states is Van- Neumann entropy, which is why Van-Neumann entropy is also called entanglement entropy. In this work, to calculate the entanglement of a three-particle atom called the Moshinsky atom; first, the reduced density matrix was calculated and then using the coordinates of the three particles in the lithium atom, the entropy entanglement was calculated. We obtained the entropy of entanglement in terms of the frequency parameter related to the external coordinate field.

In the present article, we report the results of a study of the optical and spectroscopic properties of Cu ion-exchanged glasses. The well-known ion-exchange method is used and developed for the specific present work. A soda-lime glass plate is doped ionic copper nanoparticles. It is found that the initial temperature and the specific combinations of the glass substrates have essential roles in the physical properties of the produced doped glasses. Therefore, we made two different types of copper-ion-exchanged glasses: green and red colored ones. Each type has its unique optical and spectroscopic properties due to the initial conditions of the ion-exchange process. Using absorption spectroscopy, and surface plasmon resonance studies, we can conclude that the different initial temperature of the samples in the ion-exchange procedure crucially influences the color of the samples, their characteristic index of refraction, photoluminescence, and the reflection spectra. The color of the samples is related to the type and shape of the ionic Cu-clusters, formed in the glass matrix.