International Journal of Modern Physics B

Many body quantum dynamics of phonons is steadily developed by considering the various effects of anharmonicities, defects (consider as doping or impurity concentration) and electron–phonon interactions in model Hamiltonian (instead of BCS Hamiltonian) for a high-temperature superconductor (HTS). This enables to obtain the expressions for the renormalized phonon spectrum, the renormalized phonon density of states (RPDOS). The RPDOS can be resolved into diagonal and nondiagonal parts where the nondiagonal component is found highly impurity-dependent. Considering the suitable Born–Mayer–Huggins (BMH) interaction potential, the renormalized phonon spectrum, RPDOS and generalized phonon density of states (GPDOS) of the La${}_{2-x}$Sr${}_x$CuO₄ layered superconductor have been numerically analyzed and it was found that these quantities depend on doping concentration, anharmonicities, and temperature. The results are compared with the inelastic neutron scattering experimental data of GPDOS for La${}_{2-x}$Sr${}_x$CuO₄ and are found in good agreement. The ratio of deviation in GPDOS to GPDOS at critical temperature ($T_c=37.5$ K) shows the implicit difference at $T_{(55\mathrm{\text{K}})}>T_c>T_{(20\mathrm{\text{K}})}$. The impact of defects, anharmonicities, and electron–phonon interactions in the cuprate superconductors virtually modify the scenario of GPDOS and affirm a large number of exotic peaks in the spectrum.

TiN films deposited by magnetron sputtering are widely used to improve the surface properties of components and prolong their service life. However, for complex shaped workpieces, such as hoods, the shadow effect will cause the nonuniformity of thickness, structure and performance of the as-deposited films and thus reduce their service life. High-power pulsed magnetron sputtering (HPPMS) is characterized by high ionization rate of target atoms, which makes it easy to control the energy and direction of deposited particles, and then to prepare highly uniform and compact films. In this paper, TiN films were deposited on the inner surfaces of a hemispherical workpiece by HPPMS at different working pressure. The film thickness, crystallographic structure, microhardness and morphology of the films were investigated by surface profilometer, XRD, SEM and microhardness tester. The results show that the thickness uniformity of TiN film on the inner surface of the hemispherical workpiece decreases, and the uniformity of structure and hardness increase with the increase of working pressure.

The convection-controlled diffusion problem is hyperbolic in nature and its solutions tend to have numerical shocks. To solve the problem of time dependence, it is common to use finite-element method in the spatial region, while the algorithm proposed in the past with finite differential procedure is mostly limited to the fixed finite-element grid of the spatial region. We often need to use different finite-element spaces at different times, such as the spread of flame, oil and water frontier problems; so many mathematicians and engineers have set their sights on the use of dynamic finite-element space, but also put across a lot of dynamic finite-element methods in giving the general parabola problem of the variable-mesh finite-element method. The principal purpose of this paper is to adopt different spatial grids for different time layers, and project the approximate solution of the previous time layer to the present time layer to act as the initial value of the current layer to enable us deduce the stability at discrete times.

In this paper we calculate the basic thermodynamical quantities for a system of bosonic simple harmonic oscillators (BSHOs) and the corresponding system of fermionic simple harmonic oscillators (FSHOs) using a dispersion relationship similar to cases in general relativity and condensed matter physics. In the FSHO, we see negative temperatures, and in both cases we obtain finally a system of oscillators with only one effective frequency of vibration. Also we see that pressure is less than zero for T$<$T_c where T_c is the critical temperature for bosons.

In this work, radiation resistance and radiation defects formation of chain semiconductor antiferromagnetic T1FeS₂ monocrystal have been investigated. The sample was irradiated by heavy ions at different doses up to 2.0×10${}^{13}$ ion⋅cm${}^{-2}$. The influence of radiation with heavy xenon ions on the structure of the irradiated layer has been studied and it has shown that, as the radiation dose increases, the number of peaks of the periodicity of the atomic clusters of the nanosize surface decreases exponentially.

Perovskite manganites DyMnO₃ thin film was grown epitaxially on LaAlO₃ (110) substrate by using pulsed-laser deposition (PLD) technique. The film showed perfectly orthorhombic crystallization and was well-aligned with the substrates. The in-plane dielectric properties of DyMnO₃ film were measured as functions of temperature (80–300 K) and frequency (120–100 kHz) by using parallel-plate interdigital electrodes (IDEs). Distinct transitions can be observed in the complex permittivity and loss tangent and the respective peaks shifted to higher temperatures as the measuring frequency increased. By the Arrhenius plots, the determined activation energy of the thermally activated dielectric relaxations was about 0.20 eV. According to the relationship of the real and imaginary parts of the complex permittivity, the in-plane dielectric properties of epitaxial DyMnO₃ thin film can be described as the universal dielectric response (UDR) behavior.

In this paper, we study the finiteness of the first meeting time between two different randomly moving particles in the fluid. The first particle moves with N-dimensional independent Gaussian jump and has a probability density function which is detailed in El-Hadidy (International Journal of Modern Physics B, Published Online with https://doi.org/10.1142/S0217979219502102, 2019). The other target moves with N-dimensional independent Brownian motion. We present some analysis that proves the finiteness of the first meeting time expected value between the two particles in the fluid.

DyFe${}_{1-x}$Mn${}_x$O₃ (x=0, 0.025, 0.075, 0.15) polycrystalline samples were prepared using a traditional solid-state reaction route. The structural, magnetic and magnetocaloric properties of these samples were investigated. X-ray diffraction patterns showed that the samples exist as single-phase crystallines without peaks. The results of the Scanning Electron Microscopy (SEM) revealed that the average size of the polycrystalline particles decreased from 4.34 to 3.00 $\mu$m as the Mn doping amount increased from 0.00 to 0.15. The magnetization versus temperature (M−T) plots showed that the order temperature of dysprosium (Dy) ions gradually decreased and the Morin-like transition temperature moved to the high-temperature region as x increased. The T${}_N^{\mathrm{\text{D}}y}$ gradually decreased from 13 to 10 K and the isotropic interaction of Fe${}^{3+}$-Fe${}^{3+}$ was weakened as x increased from 0.00 to 0.15. The polycrystalline samples appeared as pre-formed clusters. The magnetization (M−H) plots revealed that all the samples underwent a first-order magnetic phase transition. The maximum magnetic entropy change, occurring near the Curie temperature, obtained at a magnetic-field span of 7 T, was 18.2 J/kg K. The maximum cooling capacity of the polycrystalline DyFe${}_{1-x}$Mn${}_x$O₃ (x=0, 0.025, 0.075, 0.15) samples was 441 J/kg.

In order to research the localization problem of information source in a social network, this paper first constructs a complex network node model (Random-Susceptible-Infected-Recovered, R-SIR) based on cellular automata theory, and then utilizes this model to calculate the number of forwarding paths from a node to other forwarding nodes and the probability of occurrence of such forwarding paths, and presents an information source search method based on node reachability measure to locate the information distribution source in the information forwarding network. Theoretical analysis indicates that the algorithm, on the one hand, can avoid the time complexity problem brought by the maximum likelihood estimation, and on the other hand, overcome the inaccuracy problem of step number estimation in accessibility measure. Experimental results show that the algorithm has higher recognition rate and recognition accuracy for the information source in a multi-node network, and can search the information source, and is of great significance for the privacy protection of personal data.

The structural, electronic, magnetic properties of Mn₃XC (X=Al, Zn and Ga) antiperovskites have been investigated using first principles calculations based on Full-Potential Linearized Augmented Plane-Wave (FP-LAPW) method. Generalized Gradient Approximation with parameterization by Perdew (GGA-PBESol) is used to take into account the electron exchange–correlation interaction. Structural optimization is performed by fitting calculated data (energy-volume) to Birch–Murnaghan equation of state. Lattice constants increase in the order Mn₃AlC$\to$Mn₃GaC$\to$Mn₃ZnC. Electronic results show that there is no bandgap near the Fermi level. While the magnetism in these compounds is derived mainly from Mn atom. Finally, thermodynamic properties, including bulk modulus, heat capacities, thermal expansion and Grüneisen parameter, are computed using quasi-harmonic Debye model and analyzed in detail.

In this paper, the stochastic resonance (SR) in a periodic potential system driven by cross-correlated noises and periodic signal is investigated. The signal-to-noise ratio (SNR) is used to characterize the SR. Using the algorithm of fourth-order Runge–Kutta, we obtain the curves of SNR for different parameters. The effects of some system parameters, additive Gaussian white noise and multiplicative Gaussian colored noise intensity on SR are characterized by analyzing SNR curves. When increasing system parameter and noise cross-correlation strength in SNR-D, the SR of the system can be enhanced. However, the SR will be weakened by increasing other parameters. Otherwise, the phenomena in SNR-Q are opposite to in SNR-D when increasing signal amplitude and correlation time.

AgCu${}_{1-x}$Fe${}_x$S compounds were synthesized by partial Cu$\to$Fe replacement in the AgCuS crystal at a concentration range of 0$\le$x$\le$0.03. In the differential thermal analysis spectrum obtained at a temperature range of 300 K$\le$T$\le$1300 K, endoeffect corresponding to the structural phase transition in the AgCuS compound was observed at the temperature T=938 K. It has been determined that this result is also observed in the AgCu${}_{0.99}$Fe${}_{0.01}$S compound obtained by partial replacement of Cu atoms by Fe atoms. However, in the compound of AgCu${}_{0.97}$Fe${}_{0.03}$S this effect was observed at higher temperatures. The thermal capacities and enthalpies of phase transitions were calculated for the given compounds.

The electronic and elastic properties of ${\mathrm{\text{A}}}^{\mathrm{\text{II}}}{\mathrm{\text{B}}}_2^{\mathrm{\text{III}}}{\mathrm{\text{C}}}_4^{\mathrm{\text{VI}}}$ defect-chalcopyrite semiconductors have been studied using first-principle density functional theory (DFT) calculations. The lattice constants, energy band gap, elastic stiffness constants, bulk modulus, shear modulus, shear anisotropy factor, Young’s modulus, Debye temperature, Poisson’s ratio and B/G ratio have been computed. The values of elastic constants of 14 defect-chalcopyrites and Debye temperature for 18 compounds have been reported for the first time. The obtained results are in reasonable agreement with the experimental values in few cases where experiments are performed and reported values.

The ab initio calculation is performed to investigate about the structural and the electron transport properties of the experimentally reported (parent) compounds viz., BaFe₂As₂, SrFe₂As₂, CaFe₂As₂ and the novel compounds which are anticipated from our computational work namely BaFe₂Bi₂, SrFe₂Bi₂, CaFe₂Bi₂ with different magnetic order. The space group of the reported compounds is I4/mmm (139) and belong to ThCr₂Si₂ type. The formation energies of the reported compounds are compared in the anti-ferromagnetic (AFM), nonmagnetic (NM) and ferromagnetic (FM) orders. From the comparison, it reveals that the anti-ferro magnetism is the stabled state for the reported compounds. At ambient temperature with constant relaxation time, the resistivity, power factor, Seebeck coefficient and electrical conductivity are computed by using BoltzTraP transport theory code. To explain the superconducting nature of the novel compounds the transition temperature (T${}_C$), electron–phonon coupling factor and Debye temperature are calculated and presented. The mechanical stability of the compounds is examined by using Young’s, bulk and shear modulus, anisotropy constant and Poisson’s ratio which are calculated by using Tetra-elastic code. The Mechanical Temperament of these compounds is analyzed by using Pugh’s ratio. The ELATE tool is used to visualize the elastic properties of these compounds. The thermodynamical stability of the compounds is examined by using Gibbs free energy, vibrational Helmholtz free energy and entropy which are calculated by using Gibbs2 code. All the properties of the theoretically predicted (novel) compounds are analyzed and compared with their parent (experimentally reported) compounds.