Indian Journal of Physics最新文献

This study investigates the structural evolution of even-even tungsten isotopes ((^{154text {--}264})W) using covariant density functional theory (CDFT) with four relativistic functionals: DD-ME1, DD-ME2, DD-PC1, and DD-PCX. Key nuclear properties, including binding energies, quadrupole deformation parameters, two-neutron separation energies, neutron pairing energies, nuclear radii, and potential energy curves, are analyzed to explore shape transitions and stability from neutron-deficient to neutron-rich isotopes up to the drip line. The results reveal a dynamic shape evolution, with spherical configurations at (N = 82) and (N = 126), prolate dominance in intermediate regions, and shape coexistence in isotopes such as (^{158})W, (^{160})W, (^{194})W, (^{196})W, (^{206})W, and near (^{244text {--}248})W. A potential subshell closure at (N = 118) is identified, supported by anomalies in separation energies and vanishing pairing energies. The neutron drip line is predicted at (N = 184), marked by a return to spherical symmetry. Comparisons with experimental data and other theoretical models, including the deformed Hartree-Fock-Bogoliubov method with the Skyrme SLy4 interaction, the Finite Range Droplet Model, and the Relativistic Mean Field model with NL3, show strong agreement, validating the robustness of CDFT. These findings enhance our understanding of nuclear structure in the medium-to-heavy mass region and provide insights relevant to r-process nucleosynthesis, thereby guiding future experimental studies at radioactive ion beam facilities.

We investigate the double perovskite compound Ba₂NiUO₆ and its electronic, magnetic, elastic, thermodynamic, and thermoelectric characteristics. Specifically our research demonstrates that Ba₂NiUO₆ crystallizes in a stable cubic structure ( left( {{text{Fm}} - bar{3}{text{m}},} right. ) a = 8.292 Å) and functions as a half-semiconductor with a direct band gap of 1.47 eV (spin-up) and an indirect band gap of 1.58 eV (spin-down). In addition the compound exhibits a total magnetic moment of 2 µB, primarily from Ni 3d orbitals, while phonon dispersion analysis confirms the dynamical stability with minimal imaginary frequencies. Moreover the elastic constants indicate that the material is mechanically stable and maintains a well-balanced ductile–brittle characteristic. The thermoelectric investigations further demonstrate optimal performance at low temperatures, achieving ZT = 1 in the spin-down channel. Furthermore, thermodynamic properties, including a high Debye temperature (521 K) and favorable heat capacities, underscore its suitability for practical applications. Hence, Ba₂NiUO₆ is identified in this work as a multifunctional material that enables new applications in spintronic devices, energy conversion, and sustainable technology.

This study investigates two types of photonic crystal structures: those with fixed lengths and those with variable lengths. A comparison is made between dielectric/dielectric and dielectric/plasma photonic crystals. We employ a novel asymmetric layer arrangement that we have recently developed. The analysis examines the effects of various parameters—such as the number of layers, the smallest unit length of the proposed crystal, the magnitudes of the dielectric constants, the plasma density, and the incident angle of the electromagnetic wave—on the transmission spectra, the width and position of band gaps, and the omnidirectional band gaps. The transfer matrix method is used to calculate the transmission coefficient and to identify band gap regions in the designed structures. We demonstrate that our new proposal for a one-dimensional photonic crystal arrangement results in a tunable structure, yielding different values for optical band gaps, band gap widths, and omnidirectional band gaps.

This paper presents a novel approach for designing and analyzing a triplet optical microring resonator (TOMRR) -based optical filter. The proposed TOMRR is mathematically modelled in the z-domain using a delay line signal processing technique, where microrings are assumed to be composed of several unit delays. In this proposed TOMRR, smaller asymmetrical microrings are housed inside a larger microring to improve the space utilization factor. Asymmetrical microrings are used to increase the free spectral range (FSR) according to Vernier principle. An attempt is made to increase the FSR by increasing the number of microrings (MRRs), and it is found that the FSR increases sharply as the number of MRRs increases. The frequency response analysis of the proposed configuration is done using MATLAB software, and the obtained FSR values for the single ring, double ring, and TOMRR are 36 THz, 166 THz, and 541.4 THz, respectively. The design of the directional coupler, as well as the field analysis of the proposed configuration, is done using OptiFDTD software to depict the electromagnetic wave propagation inside the waveguide.

A comprehensive first-principles investigation is carried out to examine the electronic, optical, lattice dynamical, and thermodynamic properties of the CsLi₂Bi compound. Electronic-structure calculations reveal semimetallic character with band inversion near the Fermi level, arising predominantly from Bi-6p states, indicating the presence of nontrivial electronic features. The optical response exhibits metallic behaviour at low photon energies. At the same time, distinct interband transitions in the 2–3 eV range are associated with Bi-p–derived states, as reflected in the dielectric function, absorption spectrum, optical conductivity, and reflectivity. Phonon dispersion analysis confirms the dynamical stability of CsLi₂Bi, with acoustic and optical modes extending up to 8 THz and corresponding Raman-active vibrations. The Debye temperature increases monotonically with temperature, reaching approximately 1400 K at 1000 K, suggesting strong lattice stiffness. Thermodynamic calculations indicate a free-energy minimum around 200 K and a high-temperature heat capacity approaching ~ 85 J/mol·K due to multi-atomic contributions. These results provide a consistent physical understanding of the fundamental properties of CsLi₂Bi and establish a reliable basis for its consideration as a candidate material for further studies of electronic and lattice-driven quantum phenomena.

This paper reports the investigations to explore mechanisms of nonradiative electron transfer (ET) processes involved within donor (amino part) and acceptorfluorene of an organic short-chain dyad (E)-4-(((9H-fluorene-2yl)imino)-methyl)-N,N-dimethylaniline(NNDMBF). Furthermore,this study explores a novel aspect where Graphene Quantum Dots (GQDs) act as electron acceptors, facilitating additional electron transfer (ET) reactions within the nanocomposite system involving the donor part of the dyad and GQDs. The combined ET reaction provides valuable insight into enhancing charge separation and stability in such systems. This investigation utilizes a comprehensive array of spectroscopic techniques, including steady-state and time-resolved, alongside femtosecond (fs) transient absorption spectroscopic studies conducted across various delay times on the pristine as well as nanocomposite systems comprising (NNDMBF) the short-chain dyad and graphene quantum dots (GQDs).Since due to significant signal reduction of transient absorption species of the dyad nanocomposite systems no conclusive evidences on the formation of charge –separated species could be made possible, we have to focus our attention to the results observed from time resolved fluorescence studies. Comparing the outcomes with the pristine dyad, the results unveil a compelling narrative. The nanocomposite system appears to be a better light energy converter in comparison to pristine dyad, owing to its enhanced capacity to retain excited trans-configurations of elongated nature. This provides a significant advancement in our study on the ET mechanisms of the dyad-GQD system.

This work thoroughly examines the structural, optoelectronic, and transport characteristics of the triple perovskite halide Cs₃Bi₂Br₉ by first-principles calculations. In this calculation, we have used Perdew–Burke–Ernzerhof (PBE) Generalised Gradient Approximation (PBE-GGA) and Modified Becke–Johnson (mBJ) potential to provide enhanced band gap estimates. The determined structural parameters such as lattice constant a₀ = b₀ = 7.95 Å and c₀ = 9.84 Å and a negative formation energy, signify the thermodynamic stability of Cs₃Bi₂Br₉ compound. Electronic structure research indicates that Cs₃Bi₂Br₉ has a direct band gap of 3.22 eV using the mBJ potential and 2.50 eV using PBE-GGA. The absorption coefficient, refractive index, and dielectric function are subjected to a meticulous analysis of the material's optical properties. The findings indicate robust light–matter interactions, characterised by a significant absorption coefficient and a refractive index beyond 2.0 within the visible spectrum. Despite its relatively poor electrical conductivity, the material has distinct semiconductor properties. Cs₃Bi₂Br₉ emerges as a promising material for optoelectronic applications such as photovoltaic cells, LEDs, and optical sensors, according to our findings.

In the present research work, we explored, for the first time, structural, electronic, elastic, thermodynamic, optical and thermoelectric properties of new ScTiRuAl quaternary Heusler (QH) compound within GGA and TB-mBJ approach. The FP-LAPW method within DFT framework was used for investigation of these properties. Indirect Band gaps of 0.66 and 0.62 eV are obtained through both approaches, indicating that the considered material exhibit semiconducting behavior. The elastic and thermodynamic findings confirm that the material is both mechanically and thermodynamically stable. The optical research findings suggest that the material is well-suited for use in optoelectronic energy technologies. The power factors measured at room temperature were 6.28 × 10¹¹ Scm⁻¹ s⁻¹ using GGA and 5.92 × 10¹¹ Scm⁻¹ s⁻¹ using TB-mBJ. These results suggest that the material is suitable for applications in thermoelectric energy conversion.

As electric vehicles and portable devices become more common, battery-type hybrid supercapacitors are becoming more popular. As the name suggests, these supercapacitors store energy by intercalation, which necessitates materials that facilitate this process. For this use, stacked or planar oxide spinel materials are perfect. There is promise for creating battery-type hybrid supercapacitors by structurally intercalating oxide spinel materials. These materials’ unique crystal structures improve their capacity for energy storage by enabling the reversible insertion and extraction of ions. Compared to conventional carbon-based supercapacitors, the intercalation technique enhances ionic conductivity and charge storage capacity, leading to improved performance. An important benefit for energy storage technologies is the combination of fast charge/discharge rates from supercapacitor principles and high energy density from battery-type mechanisms. The electrochemical properties of these materials can also be improved via doping and composite creation. Oxide spinel materials, therefore, mark a major breakthrough in the search for effective and environment friendly energy storage options, opening the opportunities for further studies and progress in hybrid supercapacitor technology. The structural properties, intercalation procedure, synthesis techniques, challenges, performance-boosting strategies, and electrochemical performance of oxide spinels in hybrid supercapacitor applications are all examined in this review. In order to improve electric vehicles and other electronic devices, this review offers crucial information for creating improved battery-type hybrid supercapacitors employing oxide-based spinel materials.

By using the Particle-in-Cell (PIC) simulation method, it is verified that a dark envelope solitary wave exists in a two-temperature-ion dusty plasma. Dependence of the envelope wave amplitude, width, and velocity on system parameters such as the nonlinearity strength and the wave number is obtained from both analytical theory and numerical results. Both are in good agreement within the parameter regime where the wave amplitude and the wave number are sufficiently small. The significance lies in the understanding of wave dynamics in complex plasmas for applications in plasma communication and energy transport. A self-consistent nonlinear Schrödinger equation (NLSE) is developed and validated through analytical and PIC simulations. The findings reveal the critical role of nonlinearity and thermal effects in wave behavior, offering new insights into the stability and propagation of dark solitons in dusty plasmas, with implications for future plasma technologies.