A hybrid theoretical approach is proposed to estimate the maximum charge that a metal nanoparticle can acquire due to tunneling contact with a conducting semiconductor substrate. The method combines analytical relations and self-consistent Kohn–Sham calculations of the electron work function, ionization potential, and critical charge of an isolated particle embedded in a dielectric medium. These quantities were obtained within the framework of density functional theory (DFT) using the free electron model and subsequently adapted for noble metals. The particle capacitance is estimated using the Johnson–Kendall–Roberts contact mechanics model for both rigid and compliant dielectric spacers. It is shown that the dielectric contact region can significantly modify the ionization potential, especially for soft spacer layers. An analytical expression is derived for the maximum number of electrons that can be transferred to the particle, defining the range of attainable excess charges as a function of the spacer elastic properties. The theoretical predictions are compared with experimental data obtained from Kelvin probe force microscopy measurements of charged nanoparticles. The physical origin of the contact potential difference in Kelvin probe experiments is also discussed.

The ferroelectric–incommensurate–paraelectric phase transitions in NaNO2 are investigated by the Landau phenomenological model. The Gibbs free energy is expanded in terms of the spontaneous polarization Ps and the order parameter ψ with the bilinear (Psψ) and biquadratic (Ps2ψ2) coupling in the incommensurate phase. The spontaneous polarization Ps and the order parameter ψ are calculated as a function of temperature using literature data. By extracting the values of the dielectric susceptibility χ from the observed dielectric constant ε in the literature, its temperature dependence is also calculated for the transitions studied in NaNO2. Under the mean field model given here, the effects of the pressure and the electric field on the order parameters (Ps and ψ) and on the dielectric susceptibility χ, can also be studied for the ferroelectric–incommensurate–paraelectric phase transitions in NaNO2.

This work aims to investigate the influence of extremely low-intensity ultra-high-frequency electromagnetic radiation (UHF EMR) generated by a controlled spark discharge on the low-frequency dielectric properties of Cd1–xZnxTe (CZT) crystals and to clarify the role of point defect complexes in this process. The study focused on Cd1–xZnxTe single crystals (x = 0.10–0.20) grown from a melt under high inert gas pressure, from which rectangular samples were prepared. The real (ɛ′) and imaginary (ɛ″) parts of the complex permittivity were measured at frequencies of 1–33 kHz using a capacitive method, and the energy spectrum of localized states (LS) was determined by scanning photodielectric spectroscopy (SPDS) before and during exposure to UHF EMR. The results showed stepwise changes in ɛ′ and ɛ″ under irradiation, with relaxation effects persisting after exposure. The frequency dependence of 〈|Δɛ′|〉 and 〈|Δɛ″|〉 followed a power-law decrease. SPDS revealed a rearrangement of LS, including the disappearance of states in the Ev + 0.20–0.40 eV range and the emergence of new ones, indicating reconstruction of point defect complexes. These findings confirm that point defect complexes play the key role in the dielectric response of CZT crystals to weak electromagnetic fields and should be considered in the design of radiation detectors and electronic devices.

Two Ni–Zn spinel ferrites samples with different iron contents were investigated by quantitative X-ray diffractometry and magnetization measurements. The Fe-deficient sample was found to hold 34.4 wt% of halite phase Ni0.7Zn0.3O in addition to primary spinel ferrite phase with Ni0.6Zn0.4Fe2O4 composition, while the near-stoichiometric Ni0.7Zn0.3Fe2O4 sample contained only 5 wt% of Ni0.7Zn0.3O halite. Magnetization study indicated preferentially ferrimagnetic ordering in both samples. The coefficient of magnetocrystalline anisotropy K1 was calculated from the magnetization data using the law of approach to saturation. The results revealed significant increase of K1 in Fe-deficient sample that can be employed in microwave absorption applications.

Degenerate equilibrium states of magnets with spin s = 3/2, in which translational symmetry and the SU(4) symmetry of exchange interaction are spontaneously broken, have been investigated. The conditions of residual and spatial symmetry, leading to differential equations for the classification of such states, are formulated. For the symmetry subgroups SO(3), SO(3)×U(1), SO(3)×SO(3), SO(4), and SO(5), analytical expressions for the magnetic degrees of freedom in terms of thermodynamic parameters and spatial coordinates are obtained.

A quantitative phase analysis of substrate-free single-component and binary clusters of the Ar–Kr system obtained by adiabatic expansion of gas into a vacuum through a supersonic nozzle was performed. The studies were carried out in situ using the transmission high-energy electron diffraction technique on clusters with an average size ranging from 2 ⋅ 103 to 1 ⋅ 105 atoms/cluster and across the entire range of component concentrations. The independence of the threshold size of clusters, corresponding to the beginning of the formation of the hcp phase, from the component composition was revealed. It was established that clusters larger than this threshold size have a two-phase fcc-hcp structure with an identical concentration of components in each phase. The fraction of the hexagonal phase increases with the size of the aggregations and depends on the component content, reaching a maximum in clusters with an equimolar composition. Arguments are presented in favor of the formation of two-phase clusters in the supersonic jet, rather than separate single-phase fcc and hcp ones. These findings are in good agreement with the previously proposed thermally activated diffusion mechanism for the nucleation and growth of the hcp phase in rare gas clusters.

The effect of the partial pressure of hydrogen on the reduction processes in CeO2 nanoparticles was investigated. The surface reducibility of CeO2 upon exposition to 0.01–5 mbar and 5–402 mbar of H2 was investigated by NAP-XPS and H2-TPR techniques, respectively. Special attention was focused on studying the role of partial pressure of H2 (ranging from 5 to 402 mbar in the input gas mixture) on the H2-TPR profile. The effect of H2 partial pressure on the course of surface and bulk reduction of CeO2 was shown and discussed.

The comparative analysis of the results of low-temperature mechanical tests of the samples of amorphous and amorphous-crystalline polyimide of the Kapton H type was carried out. In the experiments [East Eur. J. Phys., No. 4, 144 (2020)], tensile diagrams σ(ɛ;T,ε˙) of such samples were recorded, namely, the dependences of the deforming stress on the strain ɛ = ε˙t at constant values of the strain rate ε˙ = 7⋅10–5, 7⋅10–4, 6⋅10–3 s–1, and temperature T = 293, 77, and 4.2 K. The initial aim of these experiments was to study the effect of moderate (77 K) and deep (4.2 K) cooling on the structure and some mechanical characteristics of polyimide, important for its use in cryogenic and aerospace engineering. Later (Low Temp. Phys. 49, 521 (2023) [Fiz. Nyzk. Temp. 49, 569 (2023)]), there was a need and opportunity to supplement the experimental results with additional analysis in order to use them to test new aspects of the theory of low-temperature elastic-viscous deformation of polymers, in particular, the description of the effects of forced elasticity and their competition with brittle fracture processes. A detailed comparison of the tensile diagrams of the polyimide samples with amorphous and amorphous-crystalline mole­cular structures performed in this study showed that at T = 293 K both structures have clearly pronounced pro­perties of the elastomers, namely, the rubber-like materials with high elasticity and the ability to reversible deformation. It has been established that amorphous samples retain these properties up to deep cooling at T = 4.2 K, and amorphous-crystalline ones only to a state of moderate cooling: at T < 77 K they acquire the properties of glassy materials with brittle fracture at the initial stage of elastic deformation. It is also shown that the kinetics of highly elastic deformation of polyimide with molecular structures of both types is due to the thermomechanical activation of soliton-like elaston excitations on molecular chains in the amorphous component of the material and is described by a nonlinear rheological equation derived earlier for the molecular model of an amorphous polymer: Low Temp. Phys. 48, 253 (2022) [Fiz. Nyzk. Temp. 48, 281 (2022)], Low Temp. Phys. 49, 228 (2023) [Fiz. Nyzk. Temp. 49, 246 (2023)]. By comparing the results of experiments and theory, an analytical description of the tension diagrams σ(ɛ;T,ε˙) of polyimide samples with molecular structures of both types was obtained, as well as empirical estimates of their rheological characteristics and microscopic parameters of elaston excitations. During low-temperature deformation of a polymer with a mixed structure, rigid crystalline fibrils immersed in the softer amorphous medium undergo only minor elastic deformations, but significantly increase the intensity of elaston activation and fracture processes in the amorphous component. Upon cooling, this leads to the convergence of critical stresses of highly elastic relaxation and fracture and to the transformation of an elastomer with such a structure into a glassy brittle material.

The resonance phenomena in a concentrated solution of 3He in 4He, arising under the propagation of the second sound in it, are investigated by the method of a vibrating quartz tuning fork located in a limiting flask. The temperature dependences of the resonance frequencies of the tuning fork are found, and the frequencies of the resonances of the second sound in a cylindrical container are calculated under conditions when the first sound is not excited. The influence of the second sound resonances on the resonance frequencies of the tuning fork is observed, resulting in distortion of the resonance line shape. It is shown that this influence decreases with an increase in the electric voltage exciting the oscillations of the tuning fork legs. The results obtained indicate a significant influence of acoustic processes in a superfluid liquid on the amplitude-frequency characteristics of the quartz tuning fork.

Carbon honeycomb (CH) cellular structures were first experimentally discovered and structurally identified almost ten years ago. They have previously demonstrated high sorption capacities for various gases. In this work, we elucidate the role of the other type of interatomic bonding in the anticipated uptake of aluminum in CH channels. The samples of CHs with the Al filled channels were prepared at three different temperatures T ≈ 25, 650, and 1000 °C. High-energy electron diffraction experiments, combined with structural modeling based on assumption of pseudophysical sorption of aluminum, not perturbing the matrices, revealed that CH structures can host metallic-like nanoscale aluminum rods within their channels. Three different mechanisms for filling the CH matrices with aluminum were found depending on the temperature. At room T we observed the direct Al vapor deposition in the wider CH channels, at T ≈ 650 °C the diffusive mechanism of sorption from the initially deposited Al films was found to prevail, while at T ≈ 1000 °C the Al films melted and in a liquid form penetrated inside the CH channels. The CH matrices, participating in the Al uptake, exhibit low densities, ranging from 1.28 to 1.55 g/cm³, indicating high porosity; the thinnest channels (in CHs with the higher densities) were filled at ≈ 1000 °C from the liquid Al phase. These findings highlight the potential of CH cellular structures as a versatile platform for creating new composite materials with metallic-like nanorods embedded in the CH channels.