Advances in Condensed Matter Physics

This paper aims to discover a novel composite material that has great potential for manufacturing high-performance supercapacitors suitable for diverse applications, such as electric vehicles, portable electronics, and stationary energy storage systems. Zeolitic imidazolate framework-8 (ZIF-8) doped by different concentrations up to 5 wt.% of nanosized Fe₂O₃ have been prepared (ZIF-8/Fe₂O₃). The effect of doping ratio 1, 3, and 5 wt.% on the structural and electrochemical properties of ZIF-8/Fe₂O₃ has been investigated. The structural characterization has been carried out using TGA, BET, XRD, and FTIR. The XRD analysis revealed that the crystalline size of our sample increased by approximately 16% as a result of doping ZIF-8 with 5 wt.% of Fe₂O₃. The structural analysis of the doped samples revealed that the material exhibited enhanced thermal stability and porosity, with an increase of approximately 105 m²/g. The introduction of doped nanometal oxides improved the capacitance value of ZIF-8 by significantly increasing its surface area. Additionally, the electron transport efficiency within ZIF-8/5 wt.% Fe₂O₃/electrode is increased. The Nyquist plot decreases as the doping of Fe₂O₃ increases. This indicates a decrease in the charge transfer resistance at the electrode–electrolyte interface, which is desired in applications such as batteries, fuel cells, or electrochemical sensors where faster electron transfer is needed for improved performance.

The effect of size on the optical properties of gold nanomaterials has been studied using the theoretical Drude–Sommerfield model. The real and imaginary parts of the dielectric function of bulk as a function of wavelength due to free electron contribution and the real and imaginary parts of the dielectric function of nanogold materials as a function of wavelength due to free electron and bond electron contribution are calculated. The real and imaginary parts of the dielectric function of bulk as a function of wavelength due to the free electron contribution graph and The real and imaginary parts of the dielectric function of nanogold materials as a function of wavelength due to free electron and bond electron contributions are plotted. As we observed from the graphs, the real dielectric functions of both bulk and nanogold materials are inversely proportional to wavelength. The imaginary part of the dielectric function of bulk gold materials is independent of wavelength. At high wavelengths, the size of the gold nanomaterial is highly influenced by both real and imagined dielectric functions at high waves. As the wavelength increases, the effect of the size on the dielectric function also increases. The size-dependent dielectric function of nanomaterials is highly influenced by their optical properties and electrical structure.

The article presents the results of studies of the chemical composition, crystal structure, lattice parameters, microstructure, the valence state of the europium ion (at 300 K), electrical resistivity, and differential thermopower (6–400 K) of samples in the Eu(Cu_1 − xAg_x)₂Si₂ (0 ≤ x ≤ 1) substitutional solid solutions. A transition of the europium ion from the valence-stable state of Eu²⁺ in EuAg₂Si₂ to the state of intermediate (homogeneous) valence (IV) of the europium ion in EuCu₂Si₂ with an effective valence ϑ_eff = 2.41 (300 K) has been initiated by a successive replacement of silver atoms by copper atoms. With appropriate sample compositions, the transition passes through a Kondo-type state. The research subject is the patterns of transformations (when the composition of the sample changes), the electronic state, and, accordingly, the electronic transport properties. The simultaneous coexistence of europium ions in different electronic states is assumed. The substitutional solid solution Eu(Cu_1 − xAg_x)₂Si₂ (0 ≤ x ≤ 1) exhibits properties related to the competition between the state of the Kondo system, intermediate valence (IV), and magnetic ordering.

In this paper, the effect of a tunable dielectric core on local field enhancement, induced optical bistability, and the optical bistability domain in cylindrical core–shell nanoparticle composites are studied. The local field enhancement factor increases significantly at two resonant frequencies. The results demonstrate that the local field enhancement factor in the cylindrical core–shell nanoparticle increases when the natural attribute of the dielectric function of the dielectric core is varied by adding a dielectric function to it. Furthermore, we demonstrated that the magnitude of the imaginary part of the active dielectric core increases as the onset and offset input intensities increase. This indicates that the optical bistability or threshold width range widens as the imaginary part of the dielectric function of the dielectric core increases, thereby enlarging the threshold domain to improve system activation.

In this work, a new canonical transformation for the Anderson lattice Hamiltonian with f–f electron coupling was developed, which was further used to identify a new Kondo lattice Hamiltonian. Different from the single impurity Kondo effect, the resulted new Kondo lattice Hamiltonian only includes the spin-flip scattering processes between conduction electrons and f-electrons, while the normal process of non-spin-flip scattering is absent in this Hamiltonian, under the second order approximation. The new Kondo lattice Hamiltonian may be used to study some anomalous physical properties in some Kondo lattice intermetallic compounds.

In this study, the structural, electronic, optical, elastic, and thermodynamic properties of Ytterbium chalcogenides YbX (X = S, Se and Te) were computed within the first principles using generalized gradient approximation (GGA) as implemented in the pseudopotential plane wave approach. The equilibrium total energy for YbX (X = S, Se, and Te) was calculated as a function of the energy cutoff, k-point grid, and lattice parameter. An optimized lattice parameter of 5.6, 5.66, and 6.136 Å were calculated for YbS, YbSe, and YbTe, respectively. The energy band gaps of YbS, YbSe, and YbTe computed are 1.14, 1.32, and 1.48 eV, respectively. In addition, the low band gap (less than 3 eV) for ytterbium chalcogenides indicated that they may have potential applications in photovoltaic cells and laser diodes. Moreover, the negative dielectric function value for a certain frequency range indicates that these compounds are suitable for specific optical and microwave circuit applications. The result of elastic and thermodynamic property computation reveals that ytterbium chalcogenides are mechanically and thermodynamically stable, which can be useful in a variety of electronic device applications.