International Journal of Modern Physics B

First principles computational simulations were performed using Quantum ESPRESSO package within the framework of Density Functional Theory (DFT) in order to analyze the structural, elastic and thermo-mechanical conditions of one of the Caesium monochalcogenides (CsSe) in a bid to fill some of the theoretical information gaps in this material. The obtained optimized lattice parameter of 7.432Å from well convergence tests agreed reasonably with results from other previous theoretical works. Three independent elastic constants ($C_{11}$, $C_{12}$ and $C_{44}$) and other mechanical indices for this cubic system were determined by fitting stress–stain relationship data via Voigt–Reuss–Hill approximation (VRHA) of Quantum ESPRESSO incorporated Thermo_pw code. CsSe is elastically and mechanically stable since the elastic constants fulfilled the Born–Huang cubic mechanical stability criteria of forms: $C_{11}+2C_{12}>0$; $C_{11}-C_{12}>0$ and $C_{44}>0$. The resistiveness of CsSe to recoverable deformation under applied force was studied via elastic moduli: bulk (B), Young (E) and shear (G) moduli. Pugh’s ratio ($\frac{B}{G}=2.40$) $>1.75$ depicted ductility and the positive value of Cauchy pressure: $C_p=C_{12}-C_{44}=0.51$GPa further confirmed the ductile nature of this system. Poisson ratio, $\varphi =0.30$, within the domain of 0.25 and 0.42, classified the compound as a metallic bonded specie. One of the three estimated sound velocity variants for the system best predicted the average Debye temperature. Some other important structural and thermo-mechanical-related parameters such as Zener anisotropy, elastic constants based Debye temperature, average speed of sound, Lame’s constants, Kleinmann parameters, hardness (micro and macro) and melting temperature were determined. The interdependencies of these obtained parameters were established and reported.

Electromagnetic induction plays a key role in regulating the electrical activity, excitability, and bistable structure of neurons. In this paper, a discontinuous control strategy with membrane potential as the threshold is introduced to the HR neuron model under the influence of electromagnetic field (EMFN model), and then we establish a Filipov EMFN neuron model to realize the regulation effect of electromagnetic field on the neuron system. Specific work of this paper reads as follows: first, the existence and stability of equilibrium points of two subsystems are analyzed by using MatCont software; second, the bistable region and its internal mechanism are discussed in detail by two-parameter bifurcation analysis; third, the mechanism of bistability and a series of complex sliding mode dynamics including sliding segment and sliding bifurcations are further revealed with the help of the fast–slow variable dissection method; finally, based on Hamilton energy, the regulation of threshold on chaotic discharge in the Filippov EMFN neuron model is explored. The numerical simulation results show that the EMFN neuron model can produce the corresponding sliding limit cycle and sliding bursting behaviors under the influence of the threshold control strategy, meanwhile, the chaotic behavior of the new system can be controlled effectively within a certain range. The results provide ideas for controlling the effects of electromagnetic fields on the biological neuronal system and exploring the regulation mechanism of neurological diseases.

This work investigates the effect of band structure, optical spectra, computed elastic coefficients, Bulk-to-Shear modulus ratio, Young’s modulus and Poisson’s ratio in metal selenide compounds and their influence on electronic, optical, and elastic properties of bulk crystals using density functional theory (DFT). By studying the structural and geometrical parameters, we show that the V–VI group compound has a direct bandgap of 0.887eV and the band structure can be explained by a partial density of states (PDOS) plot. By using Pugh’s formation, the bulk-to-shear ratio can be significant in precisely determining the ductility of a material. Poisson’s ratio can provide information to examine whether the lattice crystal is ionic or covalent. Our elastic data show that the orthorhombic system is found to be unstable. The optical spectra (high absorption coefficient of $1.78\times 10^5$cm${}^{-1}$, dielectric coefficient of 8.61 and reflective index of 2.93) of our current work would be beneficial to explore the applications of optoelectronic devices, especially in light-harvesting materials, covering the UV region. Our findings advance the knowledge of the structural, electronic, optical, vibrational, and mechanical properties of Sb₂Se₃, the key to their use, and explained the potential applications in photovoltaics perspectives.

The Fitzhugh–Nagumo equation is an important nonlinear reaction-diffusion equation used to model the transmission of nerve impulses. This equation is used in biology as population genetics, the Fitzhugh–Nagumo equation is also frequently used in circuit theory. In this study, we gave solutions to the fractional Fitzhugh–Nagumo (FN) equation, the fractional Newell–Whitehead–Segel (NWS) equation, and the fractional Zeldovich equation. We have obtained exact solutions within time fractional conformable derivative for these equations.

In order to study the influence of solid particles in lead–bismuth alloy on the safety of nuclear main pump, DPM (Discrete Phase Model) is used to calculate the wear rate of the impeller of nuclear main pump under different operating conditions. By comparing the erosion rate and the most severe erosion area under different working conditions, the most unfavorable operating conditions are obtained. The results show that the erosion of impeller caused by solid particles is the most serious when the inlet velocity of particles u is 0.4m/s and particle size D is 100$\mu$m. Under the small particle size, the impeller erosion concentrated on the suction side of the blade, and under the large particle diameter, the erosion concentrated on the pressure side, and the erosion is more serious. With the increase of solid particle velocity, the erosion of the impeller increases first and then decreases. The erosion severity of impeller and front and rear cover plates caused by solid particles is not consistent. The above research can provide guidance for the anti-wear design and safe operation of the nuclear main pump impeller.

This work reports first-principle calculations for LiMgP half-Heusler compound doped by the transition metal elements Cr, Mn, Co and Ni motivated by present findings, in which the ferromagnetism conduct is predicted. The studied LiMg${}_{0.95}{Y}_{0.05}$P alloy ($Y=\mathrm{\text{Cr}}$, Mn, Co and Ni) showed the ferromagnetic behavior. The calculations revealed that the main contributions to the net magnetization come from Cr, Mn, Co and Ni. The Cr${{}^2}^{+}$ will have four electrons, in which 2 electrons are in $e^{+}$ and other 2 occupy the $t_2^{+}$. Then, this orbital is set on the Fermi level. For LiMg${}_{0.95}$Co${}_{0.05}$P alloy, the half-metallic conduct is estimated with 100% polarized on the downside of the Fermi level. Also, LiMg${}_{0.95}$Ni${}_{0.05}$P alloy exhibits the half-metallic conduct on the downside of the Fermi level which is occupied by $t_2^{-}$ minority state. This study stated that electronegativity and magnetic properties have correlation with regard to Cr-, Mn-, Co- and Ni-doped LiMgP, in which the trends of partial moments, electronegativity and total moments are $M^{\mathrm{\text{Ni}}}<M^{\mathrm{\text{Co}}}<M^{\mathrm{\text{Cr}}}<M^{\mathrm{\text{Mn}}}$; ${\chi }^{\mathrm{\text{Ni}}}>{\chi }^{\mathrm{\text{Co}}}>{\chi }^{\mathrm{\text{Cr}}}>{\chi }^{\mathrm{\text{Mn}}}$ and $M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Ni}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}<M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Co}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}<M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Cr}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}<M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Mn}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}$.

This study investigates novel exact solutions to the conformable resonant Schrödinger equation. For this purpose, two reliable techniques are employed involving the generalized Kudryashov and exponential rational function procedures. The 3D graphics of some obtained solutions are also given. The investigated equation is very important to the field of ocean engineering and science because many wave phenomena including water waves and rogue waves can be explained with the help of the nonlinear Schrödinger equation.

In this paper, we study a nonlinear fractional Damped Burger and Sharma–Tasso–Olver equation using a new novel technique, called homotopy perturbation transform method (FHPTM). There are three examples used to demonstrate and validate the proposed algorithm’s efficiency. This nonlinear model depicts nonlinear wave processes in fluid dynamics, ecology, solid-state physics, shallow-water wave propagation, optical fibers, fluid mechanics, plasma physics, and other applied science, engineering, and mathematical physics disciplines, as well as other phenomena. Numerous algebraic properties of the fractional derivative Caputo–Fabrizio operator are illustrated concerning the Laplace transformation to demonstrate their utility. Different graphs and tables compare the results obtained by R. Nawaz et al. [Alex. Eng. J. 60, 3205 (2021)] and M. S. Rawashdeh [Appl. Math. Inform. Sci. 9, 1239 (2015)]. The proposed scheme accelerates the convergence of the series solution and guarantees the convergence associated with the homotopy parameter. Furthermore, the physical nature of various fractional orders has been captured in plots. The obtained results demonstrate that the employed solution procedure is dependable and methodical in investigating the behaviors of nonlinear models of both integer and fractional orders.

In most of practical situation multiple slips (velocity, temperature and concentration) has importance in manufacturing, medicinal, imaging processes and design of materials. In view of this, the present work considered the multiple slips on Magneto hydrodynamic (MHD) dissipative non-Newtonian fluid (Casson fluid) above a curved type of a stretching surface are studied. Multiple slips with Casson fluid have significance in controlling the blood flow distribution in human and animal bodies. The R–K fourth-order via shooting technique is used to convert the nonlinear governing equations. The impact of governing parameters is shown and explored graphically. The present investigation explores the multiple slip effects in governing equations under the influence of the magnetic field; the fluid’s temperature and velocity have reverse characteristics. In a few unique situations, the current findings have been in reasonable agreement with the current results. As opposed to when viscous dissipation is absent, the temperature distribution is higher when viscous dissipation is present. It helps us to decide depending on the industrial and manufacturing processes, whether dissipation has to be applied or not. The stretching parameter enhances the Skin friction coefficient and rate of heat transfer, while decreases the rate of mass transfer. Also, the fluid’s temperature decreases because an increase in Casson fluid parameter enhances the plastic dynamic viscosity, which creates resistance in the fluid motion.

In this research, we investigated the gap-to-$T_c$ ratio of LaH${}_{10}$ and LaD${}_{10}$ superconductors by using modification of the BCS theory. The assumption of carriers under high pressure was in a new state, revealing a novel dispersion relation and providing a peak located in density of state. The precise formula of the gap-to-$T_c$ ratio was derived and achieved. The numerical results were examined, and subsequently a greater value than the one in the BCS was obtained. Our gap-to-$T_c$ results showed the best fit with the first-principle calculation of LaH${}_{10}$ ($R=4.32$–5.25) and LaD${}_{10}$ ($R=4.39$–5.20) superconductors. Finally, those results were carried out to the gap-to-$T_c$ ratio of metal-hydrides such as H₃S, CaH₆, YH₄, YH₆, YH₇, YH₉, CeH₉, CeH${}_{10}$, ThH₉ and ThH${}_{10}$ yielding the positive outcome and interpretation.