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Silver (Ag), not only alters the electrical and optical properties of ZnO thin films but also has the ability to enhance its ultraviolet (UV) emission. However, the mechanism for the UV emission enhancement has not been clearly understood. The study focused on optimization of the optical properties of pristine and Ag-doped ZnO films through variation of preparation and post deposition parameters. The prepared pristine and Ag-doped ZnO films were found to be polycrystalline in nature with diffraction peaks corresponding to ZnO and Ag phases. Increase in Ag and annealing temperature led to increase in the transmittance of Ag-doped ZnO films. The refractive index was found to increase with a decrease in substrate-source distance, an increase in Ag concentration, film thickness, and annealing temperature. The extinction coefficient for the analysed films was found to decrease with increase in substrate-source distance and annealing temperature, but increased with increase in film thickness. An inherent dissipation of electromagnetic energy in pristine and Ag-doped ZnO films was observed due to strong interaction between low and wide optical band gap energies of Ag and ZnO, respectively. The optical band gap energy increased with an increase in substrate-source distance, decreased with an increase in film thickness and annealing temperature at a wavelength, λ = 650 nm . The observed trends have been explained based on polarizability, reduced structural defects, thermal expansion, and lattice vibrations in pristine and Ag-doped ZnO films. The obtained optimized properties show that Ag-doped ZnO films are good candidates for optoelectronic applications. [ABSTRACT FROM AUTHOR]

The intricate relationship between electrons and the crystal lattice is a linchpin in condensed matter, traditionally described by the Fröhlich model encompassing the lowest-order lattice-electron coupling. Recently developed quantum acoustics, emphasizing the wave nature of lattice vibrations, has enabled the exploration of previously uncharted territories of electron–lattice interaction not accessible with conventional tools such as perturbation theory. In this context, our agenda here is two-fold. First, we showcase the application of machine learning methods to categorize various interaction regimes within the subtle interplay of electrons and the dynamical lattice landscape. Second, we shed light on a nebulous region of electron dynamics identified by the machine learning approach and then attribute it to transient localization, where strong lattice vibrations result in a momentary Anderson prison for electronic wavepackets, which are later released by the evolution of the lattice. Overall, our research illuminates the spectrum of dynamics within the Fröhlich model, such as transient localization, which has been suggested as a pivotal factor contributing to the mysteries surrounding strange metals. Furthermore, this paves the way for utilizing time-dependent perspectives in machine learning techniques for designing materials with tailored electron–lattice properties. [ABSTRACT FROM AUTHOR]

This study is focused on investigating the atomic dynamics and vibrational properties of thin layers of cadmium selenide with thickness ranging from 200–500 nm. The studies were carried out using Raman spectroscopy at room temperature. Raman spectra were obtained in the frequency range ν = 100-800 cm-1 . Two vibration modes were observed within the specified frequency range. It has been established that these vibration modes correspond to vibrations of Cd–Se covalent bonds. The frequency of these vibrational modes was observed to increase as the thickness of CdSe thin films increased, which was attributed to the formation of a thickness-dependent phase. [ABSTRACT FROM AUTHOR]

The intricate relationship between electrons and the crystal lattice is a linchpin in condensed matter, traditionally described by the Fröhlich model encompassing the lowest-order lattice-electron coupling. Recently developed quantum acoustics, emphasizing the wave nature of lattice vibrations, has enabled the exploration of previously uncharted territories of electron–lattice interaction not accessible with conventional tools such as perturbation theory. In this context, our agenda here is two-fold. First, we showcase the application of machine learning methods to categorize various interaction regimes within the subtle interplay of electrons and the dynamical lattice landscape. Second, we shed light on a nebulous region of electron dynamics identified by the machine learning approach and then attribute it to transient localization, where strong lattice vibrations result in a momentary Anderson prison for electronic wavepackets, which are later released by the evolution of the lattice. Overall, our research illuminates the spectrum of dynamics within the Fröhlich model, such as transient localization, which has been suggested as a pivotal factor contributing to the mysteries surrounding strange metals. Furthermore, this paves the way for utilizing time-dependent perspectives in machine learning techniques for designing materials with tailored electron–lattice properties.

We measured room‐temperature phonon Raman spectra of changchengite (IrBiS) and compared the experimental phonon wavenumbers to the theoretical ones obtained by means of the ab initio density‐functional‐theory calculations in the presence and absence of the spin‐orbit coupling effects. Combining two different excitation photon energies all the symmetry predicted Raman modes are experimentally observed. The electronic properties of IrBiS are found to be similar to the recently studied isostructural compound IrBiSe showing a large Dresselhaus spin‐orbit valence band splitting. A good agreement between the experimental and theoretically predicted Raman phonon wavenumbers is found only when the lattice parameter is constrained to the experimental value. The inclusion of the spin orbit coupling does not significantly affect the phonon wavenumbers. [ABSTRACT FROM AUTHOR]

The heat conductance across the interface between a phase change material (PCM) and the metal shell is important for thermal design of latent heat storage systems. Non-equilibrium molecular dynamics simulations were carried out in this work to unravel, at the atomistic level, the interfacial heat conductance mechanisms between erythritol (the most promising medium-temperature polyol PCM) and two different metals (i.e., copper and aluminum). The interfacial contact ratio was introduced as a parameter to represent different contact conditions at the interfaces, for example, different surface roughness levels of the metals. It was found that with the increase of interfacial contact ratio, the temperature difference between the erythritol/metal interfaces decreases, whereas the interfacial heat transfer coefficient increases gradually. At the perfect contact condition, i.e., the interfacial contact ratio reaches 100%, the interfacial heat transfer coefficients across the erythritol/Cu and erythritol/Al interfaces were predicted to be 398 ± 26 MW/m2K and 544 ± 11 MW/m2K, respectively. The interfacial heat conductance of erythritol/Al is better than that of erythritol/Cu. The mismatch of atomic spectral density across the interfaces between erythritol and the two metals was analyzed and distinguished. These results could guide the selection of packaging materials and the thermal design of erythritol-based latent heat storage systems.

In this study, the manganites Nd 0.5 Ca 0.5 MnO 3 , Nd 0.5 Sr 0.5 MnO 3, and Pr 0.5 Ca 0.5 MnO 3 were investigated using infrared spectroscopy. The experiments were conducted under standard conditions at room temperature, and the infrared spectra of the compounds were analyzed within the wavenumber range of 400–4000 cm−1. The observed frequencies primarily correspond to the Mn–O–Mn metal-oxygen bonds that form the MnO 6 octahedron. Additionally, in the Nd 0.5 Ca 0.5 MnO 3 and Pr 0.5 Ca 0.5 MnO 3 compounds containing calcium, extra frequencies corresponding to Ca–O bonds were also detected. • The obtained results allow us to obtain information about the atomic dynamics of Nd(Pr) 0.5 Ca(Sr) 0.5 MnO 3 compounds. [ABSTRACT FROM AUTHOR]

On the basis of first-principles electronic structure calculations, crystallographic parameters have been refined for calcium hydroxozincate (Qatranaite mineral), and the vibration properties (frequencies and eigenvectors) calculated. A detailed analysis of vibration modes is done, in the context of comparison with infrared and Raman spectra previously available. Special attention is paid to a posteriori symmetry analysis of vibration modes, discussing the latters' attribution to four irreducible representations of the P 2 1 / c space group, and to identifying stretchings and bendings of particular chemical bonds, pronounced in different vibrations. It turns out that high-frequency (> 700 cm−1) vibrations of hydroxyl groups bridging the Ca or Zn cations differ quite considerably for crystallographically distinct hydroxyl positions. It is shown that the vibrations involving hydroxyl groups and crystalline water typically come about in quadruplets at very close frequencies, whereby different irreducible representations reflect different combinations of similar "molecular" vibrations of four identical entities (of each hydroxyl or water) present in the unit cell. However, some vibrations show exceptions from this rule. In addition to interpretation of earlier experimental investigations, our study indicates that the low-frequency (< 700 cm−1) vibrations within the cation–hydroxyl connected skeleton are of more "solid-state-like" character and cannot be reasonably interpreted in terms of "molecular" vibrations within ZnO 4 or CaO 6 units. [Display omitted] • Projection of vibration eigenvectors according to different criteria is suggested. • Contributions from different stretchings and bendings are naturally identified. • Molecular-type vibrations make almost degenerate symmetry-constrained combinations. • Vibrations throughout metal-oxygen cages make a dense quasi-continuous spectrum. [ABSTRACT FROM AUTHOR]

The investigation of the Raman and Infrared phonons has been done for the tetragonal Ruddlesden-Popper compounds Barium Orthorhodate, Barium Orthoiridate, Barium Orthoplumbate, and Barium Orthostannate having phase I4/mmm and symmetry D4h17 using normal coordinate analysis. With three stretching and six bending force constants, the zone center vibrational modes have been calculated. For the first time, the assignments for the Raman and infrared wavenumbers for the tetragonal compounds Barium Orthorhodate and Barium Orthoplumbate have been reported using Wilson's GF-Matrix Method. The infrared wavenumbers for the compounds Barium Orthostannate and Barium Orthoiridate have been assigned theoretically in I4/mmm phase. A significant correlation of the cation Rhodium, Iridium, Tin, and Lead has been studied for the various vibrational modes providing insight into the structure of the investigated Barium Orthorhodate, Barium Orthoiridate, Barium Orthoplumbate, and Barium Orthostannate compounds. The force constants containing the cation Rhodium, Iridium, Tin, and Lead follow a predictable pattern and also exhibit changes in values as the atomic orbit varies. Further, as the atomic number varies, the vibrational modes that are governed by the cation Rhodium, Iridium, Tin, and Lead take on a distinct nature demonstrating that the size of the cation has a significant impact on the vibrational properties. The potential energy distribution for each normal mode in the tetragonal structure of the Ruddlesden-Popper phase of Barium Orthorhodate, Barium Orthoiridate, Barium Orthoplumbate, and Barium Orthostannate crystals have been analyzed and the contributions of stretching and bending force constants toward different vibrational modes have been calculated. [ABSTRACT FROM AUTHOR]

We study the coupled macroscopic and lattice wave propagation in anisotropic crystals seen as continua with affine microstructure (or micromorphic). In the general case, we obtain qualitative information on the frequencies and the dispersion relations. These results are then specialized to crystals of the tetragonal point group for various propagation directions: exact representation for the acoustic and optic frequencies and for the coupled vibrations modes are obtained for propagation directions along the tetragonal c -axis. [ABSTRACT FROM AUTHOR]

Mixed tin‐lead halide perovskites are promising low‐bandgap absorbers for all‐perovskite tandem solar cells that offer higher efficiencies than single‐junction devices. A significant barrier to higher performance and stability is the ready oxidation of tin, commonly mitigated by various additives whose impact is still poorly understood for mixed tin‐lead perovskites. Here, the effects of the commonly used SnF2 additive are revealed for FA0.83Cs0.17SnxPb1−xI3 perovskites across the full compositional lead‐tin range and SnF2 percentages of 0.1–20% of precursor tin content. SnF2 addition causes a significant reduction in the background hole density associated with tin vacancies, yielding longer photoluminescence lifetimes, decreased energetic disorder, reduced Burstein–Moss shifts, and higher charge‐carrier mobilities. Such effects are optimized for SnF2 addition of 1%, while for 5% SnF2 and above, additional nonradiative recombination pathways begin to appear. It is further found that the addition of SnF2 reduces a tetragonal distortion in the perovskite structure deriving from the presence of tin vacancies that cause strain, particularly for high tin content. The optical phonon response associated with inorganic lattice vibrations is further explored, exhibiting a shift to higher frequency and significant broadening with increasing tin fraction, in accordance with lower effective atomic metal masses and shorter phonon lifetimes. [ABSTRACT FROM AUTHOR]

The vibrations of a diatomic linear chain exhibit two bands, the acoustic and the optical one. In the case of equal masses and nearest‐neighbor spring constants, no gap exists. The effects of nearest, next‐nearest, and third‐nearest neighbor coupling with different spring constants are analyzed. Nearest neighbor coupling leads to two topologically different bulk states with winding numbers ν = 0 and −1. Next‐nearest neighbor coupling does not change the topological properties and introduces only a trivial "Semenov" gap. Third‐nearest neighbor coupling leads to four distinct topological bulk phases with winding numbers ν=0,±1,and−2. [ABSTRACT FROM AUTHOR]

The mobility of high-frequency discrete breathers in monatomic chains with nonlinear interatomic potentials of the nearest neighbors is considered. It was found that the odd (cubic and fifth) anharmonicity strongly affects the mobility of breathers, sharply increasing the distance that it propagates without being trapped. It was also found that the correctly chosen fifth anharmonicity leads to an inversion of stability between the bond-centered and site-centered breathers and to the low-radiative propagation of discrete breathers along the chain. • Odd anharmonicity increases the mobility of discrete breathers in atomic chains. • Fifth anharmonicity leads to inversion of stability of discrete breathers. • Weak satellites were observed in kinetic energy spectra of moving discrete breathers. [ABSTRACT FROM AUTHOR]

Abstract—The effect of low-dose γ radiation on the mechanisms of low-frequency conductivity of mesoporous silicon has been studied. It has been shown that γ irradiation preserves the hopping character of conductivity at a change of the frequency of phonon lattice vibrations, a decrease in the size of the hop, and a shift of the level of the capture of traps to the Fermi level in the band gap, which makes the structure with mesoporous silicon irradiated by γ radiation promising for the creation of multifunctional resistive and capacitive devices. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the results of studies the Raman spectra of Ni1‐xZnxFe2O4 (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1.0) ferrites nanopowders at room temperature and spectral range from 50 to 2,000 cm−1. The interpretations of the Raman spectra are given. The analysis of the results showed that spectra of compositions contain of maxima interpreted by us as oscillations of magnetic sublattices. The intensities of these maxima correlated with changes of Ni and Zn concentrations in compositions and, accordingly, of total spins concentration. [ABSTRACT FROM AUTHOR]

We discuss a two‐dimensional model that leads to results which reproduce, at least qualitatively, some of the experimentally observed features of spin‐conversion compounds. The molecules of these compounds have two electronic energy levels separated by Δ. The values of the elastic constants of the springs contained in the molecules are lower in the upper level. Consequently, the phonon branches of the crystal depend on the electronic states of the molecules. The fundamental level is a low spin (LS) state and the excited one is a high spin (HS) state. We study the thermal variation of the high spin fraction, i.e., the fraction of molecules in the (HS) level by using a model of atom‐phonon coupling with a boundary effect: Δ = Δb for molecules within the bulk, and Δ = Δse < Δb for molecules on the boundary. These values are compound‐dependent, but independent of the size of the crystal. Our results qualitatively reproduce two seemingly contradictory experimental results as well as the disappearance and reappearance of the hysteresis loop that is observed when the number N of molecules of the crystal is very small. Our model explains why the width of the hysteresis loop decreases with decreasing N. We find that, for any number of molecules, the entropy of the crystal vanishes at 0 K, in accordance with the third law of thermodynamics. [ABSTRACT FROM AUTHOR]