International Journal of Modern Physics B

The Half Heusler alloy (HHA) MnCrP has been studied theoretically for structural, elasto-mechanical and phonon properties. The structure is optimized and the calculated structural parameters are close to the literature. This optimized data is used to estimate three independent second-order cubic elastic constants $C_{11}$, $C_{12}$ and $C_{44}$. The mechanical stability criteria are explored by these constants and further used to estimate the elastic moduli; Young’s, bulk and shear modulus. The mechanical parameters like Poisson’s ratio, Pugh’s ratio, anisotropic factor, Cauchy pressure, shear constant, Lame’s constants, Kleinman parameter are also calculated and discussed. Discussions reveal the ductile nature, ionic behavior, anisotropic nature and mechanical stability of MnCrP. The metallic nature, compressibility, stiffness and interatomic forces of material are also described. Furthermore, the Debye temperature, where the collective vibrations shifts to an independent thermal vibrations, is also calculated. Longitudinal and transverse sound velocities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of the alloy as no negative phonon frequencies in the phonon-dispersion curves. These curves are used to estimate the reststrahlen band where light reflects 100% and the suitability of material is checked for Far Infrared (FIR), photographic, optoelectronic devices and sensors.

Emerging connected autonomous vehicle (CAV) technologies provide an opportunity to the vehicle motion control to improve the traffic performance. This study simulated and evaluated the CAV-based speed and lane-changing (LC) control strategies at the expressway work zone in heterogeneous traffic flow. The control strategies of CAV are optimized by the multi-layer control structure based on model predictive control. The heterogeneous traffic flow composed of human-driven vehicles and CAVs is constructed based on cellular automata by the proposed Expected Distance-based Symmetric Two-lane Cellular Automate (ED-STCA) LC model and CAV car-following model. The six control strategies composed of variable speed limits (VSL), LC and their coordinated control strategies are experimented. The average travel time and throughput are selected to assess the advantages and disadvantages of each strategy under each combination of vehicles’ arrival rates and CAV mixed ratios. The numerical results show that: (i) the effect of the control strategy on the traffic is not obvious under free flow, and the control strategy may worsen the traffic under medium traffic. (ii) Early lane-changing control (ELC) is better than late lane-changing control (LLC) under medium traffic, and LLC is better under heavy traffic. (iii) $\mathrm{\text{ELC}}+\mathrm{\text{VSL}}$ is the best choice under heavy traffic and the mixed rate of CAVs is high. The simulation results obtained in the paper would provide some practical references for transportation agencies to manage the traffic in work zone under networking environment in the future.

Theoretical investigation and computer simulation of the evolution of terahertz (THz) radiation in a two-level resonance gain medium was carried out on the basis of Maxwell–Bloch equations, using the slowly varying amplitude approximation. The gain medium is based on a system of noninteracting parallel-oriented metallic carbon nanotubes and nanoribbons. Considering the Maxwell–Garnett theory (MGT), the effective dielectric function (EDF) of the medium was obtained. Due to the large nanotube dipole moment (or large value of oscillator strength) not only THz radiation occurs, but also a totality of periodic pulses generation. Results of simulation totally coincide with the theoretical ones. The equation for the phase by analogy with the self-induced transparency (SIT), taking into account the dissipative processes, was obtained. The obtained equation describes a mathematical pendulum, where friction force is proportional to the velocity and directed to the opposite of particle movement. The friction leads to the fact that the pendulum makes a full rotation around the axis or decays, depending on the absorption properties of a gain medium. It was shown that at the certain properties of a gain medium, the equation coincides with the well-known Sine-Gordon equation. It was obtained, that at the initial pumping $6\times 10^{20}$ m${}^{-3}$ and at the volume fraction of nanoparticles about 10${}^{-7}$, the stationary value of radiation energy in a resonator is about 1 J/m³.

The phase transition in information spreading was investigated. Two phase transitions were studied, respectively, from the point of view of network information and the node information, and the corresponding simulations were implemented on high-order networks. In order to explore the phase transition in information dissemination, this paper analyzes the characteristics of social networks and constructs a high-order network model with explicit, subexplicit, and implicit relationships. The factors affecting interpersonal communication were analyzed, the social cumulative effect was introduced, and two transmission models with characteristics of permanent forgetting and temporary forgetting were proposed. The comparison between simulated experiment and real case shows that the network mode accord with the characteristics of the actual network, and the two models of phase transitions are closer to the actual.

In this work, spatially resolved characterization methods are used to identify loss mechanisms for common $p$-type silicon solar cell architectures, including multicrystalline aluminum back surface field (Al-BSF), monocrystalline Al-BSF, monocrystalline passivated emitter and rear cells (PERC), and bifacial monocrystalline PERC. The characterization methods used in this work include suns-$V_{\mathrm{\text{OC}}}$, photoluminescence imaging, and spatially resolved external quantum efficiency and reflectance measurements. The optical and recombination losses are driven by the material properties, cell processing conditions, and device architecture. These losses are quantified and categorized in terms of underlying mechanisms (e.g., front reflectance, escape reflectance, front recombination, and parasitic optical absorption and recombination in the bulk and rear). The ability to create images of these loss parameters can be used to gain more insight into the materials and manufacturing processes used to produce solar cells, and examples are given in this work to illustrate how these images can help reveal the origin of defects.

Based on Monte Carlo simulation, the magnetic properties of a mixed spin-1 and spin-3/2 Ising superlattice with alternate layers are studied. The effects of interlayer coupling and external magnetic field on the compensation behavior and hysteresis properties for the ferrimagnetic superlattice are investigated. The occurrence of a compensation point is found to be greatly affected by the interlayer coupling. In particular, various multiple hysteresis loops can be observed under certain system parameters. The calculated results agree well with available experimental and theoretical works.

A theoretical study of SmXO₃ ($\mathrm{\text{X}}=\mathrm{\text{Al}}$, Co) cubic perovskites for vibrational properties and Reststrahlen band is done within the framework of Density Functional Perturbation Theory (DFPT) implemented in Quantum ESPRESSO. The vibrational properties of the Samarium-based perovskites are figured using Martins–Troullier pseudo potentials. The phonon density of states and phonon dispersion curves in first Brillouin zone are computed and discussed in which two optical phonon frequencies, ${\omega }_{\mathrm{\text{TO}}}$ and ${\omega }_{\mathrm{\text{LO}}}$, are targeted to find Reststrahlen band for these materials. No imaginary frequency was noted, which shows the structural stability of both perovskites in cubic state. Reststrahlen bandgap and Lyddane–Sachs–Teller (LST) relation for these materials are calculated using optical phonon frequencies and applications are specified. Reststrahlen band of both materials is found to exist in the Far Infra-red region (ranging from 0.3 to 6.0 THz) showing that they can be identified by throwing light of Infrared region upon them in geological applications.

The first equation in a hierarchy of equations due to Vlasov is studied. The equation can be described as a Schrödinger equation for the probabilistic description of a system. It has applications in other areas as well. A physical meaning can be assigned to the phase of the wavefunction. The approach allows construction of solutions of the Schrödinger equation from known solutions and conversely much like a Bäcklund transformation. Finally, the process of introducing a potential into the Schrödinger equation is generalized to the case of Bohmian mechanics.

Complicated physical problems are usually solved by resorting to perturbation theory leading to solutions in the form of asymptotic series in powers of small parameters. However, finite, and even large values of the parameters, are often of main physical interest. A method is described for predicting the large-variable behavior of solutions to nonlinear problems from the knowledge of only their small-variable expansions. The method is based on self-similar approximation theory resulting in self-similar factor approximants. The latter can well approximate a large class of functions, rational, irrational, and transcendental. The method is illustrated by several examples from statistical and condensed matter physics, where the self-similar predictions can be compared with the available large-variable behavior. It is shown that the method allows for finding the behavior of solutions at large variables when knowing just a few terms of small-variable expansions. Numerical convergence of approximants is demonstrated.

The modified version of the generalized Mobius square (GMS) potential has been obtained by employing the dissociation energy and equilibrium bond length as explicit parameters. The potential parameters have been defined in terms of the molecular parameters. The modified GMS potential has also been used to model internuclear interaction potential curves for different states of diatomic molecules. Also, we have obtained the rotational–vibrational energy spectra of the new GMS potential model, both analytically and numerically for the different diatomic molecules. This was done by employing a Pekeris-type approximation scheme and an appropriate coordinate transformation to solve the Schrodinger equation. Our results have been compared with the experimental Rydberg–Klein–Rees (RKR) data and its corresponding average absolute deviations in terms of the dissociation energy computed. The effects of the vibrational and rotational quantum numbers on the rotational–vibrational energies for the different states of the various diatomic molecules have also been discussed. This paper has shown to be highly relevant to the studies of thermodynamic and thermochemical functions of diatomic molecules.

In this paper, the plane wave ultra-soft pseudopotential method was performed to analyze the effect of neutral Zn vacancy (V${}_{\mathrm{\text{Zn}}}$) and O vacancy (V${}_{\mathrm{\text{O}}}$) on the electronic and magnetic properties of Mn-doped ZnO systems. In a $2\times 2\times 2$ ZnO:Mn supercell, the sites of V${}_{\mathrm{\text{Zn}}}$ and V${}_{\mathrm{\text{O}}}$ were set as nearest neighbor, next nearest neighbor and far nearest neighbor relative to Mn site, respectively. The results indicated that V${}_{\mathrm{\text{Zn}}}$ is easier to be produced than V${}_{\mathrm{\text{O}}}$ in the ZnO:Mn system, and both kinds of defects are more likely to be generated in the nearest neighbor of Mn site. Meanwhile, the ZnO:Mn-V${}_{\mathrm{\text{Zn}}}$ system is p-type conductive. The farther the distance between V${}_{\mathrm{\text{Zn}}}$ and Mn, the better the conductivity of the system. Contrary to V${}_{\mathrm{\text{Zn}}}$, the ZnO:Mn-V${}_{\mathrm{\text{O}}}$ system is n-type conductive. The farther the distance between V${}_{\mathrm{\text{O}}}$ and Mn, the worse the conductivity of the system. Furthermore, the ZnO:Mn systems containing neutral V${}_{\mathrm{\text{Zn}}}$ or V${}_{\mathrm{\text{O}}}$ are both likely to be in antiferromagnetic phase. However, the presence of V${}_{\mathrm{\text{Zn}}}$ will enhance the possibility, while V${}_{\mathrm{\text{O}}}$ will weaken it.

The structures, electronic and magnetic attributes of the transition metal (TM) doping Mg₉O₉ tubular clusters have been investigated using the PBE functional. The results display that the ScMg₉O₉ and NiMg₉O₉ clusters are more structurally stable than the other TMMg₉O₉ clusters. An Sc atom replaces the Mg atom at the edge site of the Mg₉O₉ clusters, which leads to the Mg atom transferring to the top of an adjacent O atom. Ni atom prefers to occupy the bridge site of the Mg–O bond at a side of the Mg₉O₉ clusters. VMg₉O₉ and FeMg₉O₉ display more kinetic activity than the other TMMg₉O₉ clusters. The TM atoms lost certain electrons except for Co, Cu and Zn. The maximum spin value of the TM atoms for the ground-state TMMg₉O₉ clusters occurs at Mn.

A quantum heat engine (QHE) model by considering as working substance two spins (spin-1, spin-$\frac{1}{2}$) is proposed. It consists of using different Heisenberg models with the Dzyaloshinskii-Moriya (DM) interaction in the presence of magnetic field $B$. The proposed model contains four stroke two isochoric and two others adiabatic. A comparison of different models such that $XXX$, $XXZ$ and $XYZ$ is examined for various thermodynamics quantities, especially the efficiency $\eta$ and work $W$. Finally, discussion and interpretation all results are given in the last section.

We have theoretically studied the designable quantum beamsplitter of single photons interacting with the two-level quantum dot placed in the node of a Y-type waveguide on the basis of the real-space approach. We showed that splitting of incoming single photons from one quantum channel to the others could be achieved by controlling the coupling strength of two-level quantum dot with waveguide, detuning between the quantum dot and the incoming single photon, and so on. Such quantum devices based on the controllable single photon transport behave as quantum beamsplitter at the single photon level, which provides us rich ways of configuration of important elements for the practical realization of the quantum information network.