Indian Journal of Physics最新文献

In the interplanetary space where the magnetic field topology is complex, the Rayleigh–Taylor instability (RTI) plays an important role in fluid mixing and energy transmission. The effect of nonlinear characteristics of the RTI with different magnetic fields has been studied using Magnetohydrodynamics (MHD) simulations. The theoretical results show that the growth rate of RTI is closely related to the magnetic field. The numerical results show that during the nonlinear growth phase of RTI, the presence of the magnetic field (varvec{{B}}) has the inhibitory effect on the evolution of the mixing zone height (h_m). And the evolution of the spike width (w_s) is suppressed only with a magnetic field (B_x) which parallel to the interface of the magnetosphere.

In the current investigation, we have implemented first-principles calculations to examine the structural, elastic, electrical, and optical characteristics of LiBH₂. All of the calculations were performed using first-principles density functional theory (DFT). The space group Pnma (62) has been used. The obtained results regarding the lattice parameters of the material of interest are found to be within 2% slighter than those of the experiment. The dispersion curve shows that LiBH₂ is a semiconductor with an indirect band gap of 0.978 eV along the Y–Γ direction. The optical parameters like dielectric function ε(ω), reflectivity R(ω), index of refraction n(ω), coefficients of extinction k(ω), and absorption α(ω) are determined and explained. In this regard, LiBH₂ has shown promise on hydrogen storage applications in account of its high hydrogen volume density of 94.85 g/L (more than that of liquid hydrogen), and a gravimetric hydrogen density of 10.12 wt.%, fulfilling the standard set by US-DOE for 2025.

Hydrothermal synthesis of nickel-doped copper sulfide (Cu_1−xNi_xS) nanostructures was carried out using copper nitrate trihydrate, thiourea as sources of copper, sulfur, respectively, with CTAB serving as a cationic surfactant. The nanostructures were synthesised at concentrations of x = 0, 1, 3, 5, and 7 at% and then examined for their structural, optical, and magnetic characteristics. X-ray diffraction examination verified the presence of a hexagonal structure in the covellite phase, with no other phases detected. Surface morphology analysis reveals the presence of nanosphere-shaped structures resembling flowers. The UV–Vis spectroscopy investigation showed that the bandgap decreases as the concentration of Ni-doping rises. The fluorescence spectrophotometer was used to analyse the photoluminescence at room temperature. The analysed samples exhibited prominent emission peaks at wavelengths of 411 and 433 nm. The synthesised sample has significant promise for use in display technology, as shown by its color-correlation temperature (CCT) and Commission Internationale de L'Eclairage (CIE) values. Magnetic measurements showed that CuS nanostructures doped with Ni exhibited room-temperature ferromagnetism and changed to soft ferromagnetic material at higher concentrations.

The use of nanofluids, which are aqueous fluids containing nanoparticles, facilitates the ability to increase the critical heat flux (CHF) of a system. This study conducted pool boiling experiments at 50 °C and atmospheric pressure to examine the CHF features of CuO nanoparticles, Al₂O₃ nanoparticles, and a hybrid of Al₂O₃ and CuO colloids. Ni–Cr wire is used as the primary heating element. The concentrations of nanoparticles in the base fluid varied between 0.1 and 0.5 percent by weight, with each increase representing a doubling of the previous value. From a low of roughly 2%, the critical heat flow climbed by around 19% in each of the test conditions. The appearance of a nanofluid on the heating surface, which enhances surface wettability, is associated with an increase in CHF. The accumulation of nanoparticles on the surface of the heater also contributes to the increase in CHF. After attaining a peak at 17% at 0.2 weight%, the rate of CHF enhancement shown by hybrid nanofluid began to fall. These findings have important applications in thermal management systems used in nuclear reactors, electronics cooling, and other high-heat flow scenarios.

We discuss a generalization of constant-roll inflation models by using (beta)-function formalism for inflation in such a way that the exact constant-roll condition is asymptotically satisfied near the fixed points of the (beta)-functions, in other words, in deep inflationary phase. Several types of the (beta)-functions and the corresponding inflaton potentials which satisfy the generalized constant-roll condition are analytically found.

Magnetic phase transitions and self-organization phenomena in an open ferromagnetic Ashkin-Teller model with mixed-spin (1,3/2) variables defined on a square lattice are investigated by means of Monte Carlo simulations in the presence of competing Glauber and Kawasaki dynamics. The latter simulates spin-exchange processes between neighboring sites and flows energy into the system from an external source. The thermal behavior of the system magnetizations and macroscopic instabilities have been thoroughly studied in the model parameters’space. Rich physical properties are got, in particular first- and second-order phase transitions and multicritical points. Self-organized antiferromagnetic phases are detected when the Kawasaki dynamics becomes dominant.

In this study, we explore the thermodynamic aspects of a delta quantum dot (ΔQD) under the influence of electric and magnetic fields. By applying the Nikiforov-Uvarov approach, we derive essential thermodynamic parameters of the system, including its free energy, entropy, heat capacity, and magnetization. Understanding these properties is vital for grasping quantum dot nanostructures' dynamics and intrinsic qualities subjected to external field forces. We present detailed results and thorough discussions of the derived thermodynamic parameters, revealing their dependence on temperature and magnetic field strength. The results show a pseudo-harmonic pattern in the entropy of a delta quantum dot system, indicating distinct regimes, potential phase transitions, and their involvement in quantum coherence. Our findings shed light on the intricate interplay between electric and magnetic fields, providing valuable insights into the thermodynamic behavior of ΔQDs. This study contributes to the broader understanding of quantum dots and their potential applications in future technological advancements.

In this paper, we have Studied wet dark fluid cosmological model in the frame work of Lyra’s manifold in anisotropic Bianchi Type (VI_{0}) space time. To obtain the deterministic solution of field equation, we are using a power law, i.e. relation between metric potential (A={B}^{n}.) Stability of the obtained model is discussed with the help of sound speed. Also, we have study some observational parameters such as deceleration parameter, jerk parameter and redshift of the obtaining model. Some physical and kinematical properties of the models are discussed.

People now pay increasing attention to the green high-performanced perovskites owing to their leadlessness and thus environmental-friendliness. Double perovskites materials emerge as promising candidates. In this study, the structural, elastic, optical, and electronic properties of Cs₂YAgX₆ (X = Cl, Br, I) are simulated using the density functional theory. The calculated octahedral factor, tolerance factor, negative formation energy, and elastic constants confirm the structural stability of these materials according to the Born stability criterion. The electronic properties reveal indirect bandgaps of 3.68 eV, 3.11 eV, and 2.41 eV for the Cl, Br, and I substitutions, respectively. The calculated dielectric function, refractive index, reflectivity, optical absorption, conductivity, and energy loss, indicate intense absorption in the blue and ultraviolet regions (5–13 eV and 20–30 eV), suggesting potential application in blue and ultraviolet detectors. Notably, in the energy region of ~ 14-18 eV, Cs₂YAgX₆ exhibit metallic nature. Moreover, the real refractive index is less than 1 in the 15–35 eV range, implying superluminal phase velocity and potential use as a photon accelerator in a broad spectral region. These findings indicate the potential of Cs₂YAgX₆ as green, high-performance materials for optoelectronic applications.