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Ag 2 S doped chalcogenide glassy systems have been characterised on the basis of AC conductivity and electric modulus formalism. Various nanophases such as Ag 2 Se, Te 0.5 Se 3.5 etc. and dislocation (defects) have been identified and their roles in the conduction process have been established. XRD analysis provides that incorporation of more Ag 2 S content in the present system should play important role to enhance the dislocation and to decrease the crystallite sizes. The Fourier transform infrared spectra (FT-IR) confirm the characteristic vibration of Ag–S at 500–650 cm −1 , stretching vibrations of the O–H bond near 3400 cm −1 and bending vibrations of the adsorbed H 2 O molecules on the surface of Ag 2 S near 1600 cm −1 . Composition dependent optical phonon frequency (ν 0 ) and Debye temperature ( θ D ) have been estimated from FT-IR and it is noteworthy that θ D increases with Ag 2 S content in the compositions up to x = 0.1, but decreases for x = 0.2. This result suggests higher kinetic energy of the constituent atoms/molecules, which may refer to higher electrical conductivity due to polaron hopping. Correlated barrier hopping (CBH) model in its modified version has been found most suitable model to explore the conduction mechanism. Short time relaxation process may be considered to be trivially associated with conduction of polaron. universal scaling approach proposed by Ghosh and Pan has been adopted to interpret electrical relaxation process from time-temperature superposition principle. AC conductivity spectra at various temperatures exhibit a perfect overlap into a single master curve. This feature must be an indication of the temperature independent relaxation process. On the other hand, conductivity spectra of all the compositions at a particular temperature do not exhibit perfect overlapping into a single master curve. This result indicates that the relaxation dynamics of charge carriers (polarons) is strongly dependent on compositions.

Experimental discovery of the near-room-temperature superconductivity in highly compressed binary hydride H 3 S by Drozdov et al. (Nature 525 , 73 (2015)) inaugurated a new era in superconductivity. To date, more than 580 superconducting phases of binary hydrides have been studied. The search for near-room-temperature superconductivity is currently extending to ternary and quaternary hydrides, where one of the findings is LaB 2 H 8 phase with at (Song et al., J. Am. Chem. Soc. 146 , 13797 (2024)). Here we analysed reported experimental data for LaB 2 H 8 and determined the Debye and Einstein temperatures, the electron-phonon coupling constant , and Fermi temperature, in this phase. The obtained value of is within its uncertainty limits and is consistent with the value calculated using first-principles calculations by Song et al. The derived ratio implies that lanthanum ternary borohydride LaB 2 H 8 falls in the unconventional superconductor region of the Uemura plot. The obtained ratio implies a moderate level of non-adiabaticity in LaB 2 H 8 , which is similar to other hydrogen-rich superconductors such as H 3 S, LaH 10 , La 4 H 23 , LaBeH 8 , TaH 3 , as well as pnictides, cuprates, and MgB 2 .

In this study, we present a comprehensive exploration of the Delafossite composites using density functional theory (DFT) and the semi-classical Boltzmann simulations within the Wien2k framework. Our investigation includes structural, electronic, magnetic and thermal properties in the tetragonal phase, providing a holistic understanding of these materials. Firstly, the structural-magnetic stability of XMnZ 2 (X = Au, Hg, and Tl, Z = S, Se) was verified through ground-state energy calculations obtained from structural optimizations. Our results indicate a stable ferromagnetic phase for the six compounds. Moving on to electronic properties, we utilize the Trans-Blaha modified Becke Johnson (TB-mBJ) functional potential to elucidate the electronic behavior (metallic, half metallic, semiconductor or insolating) of the considered compounds in both up and down spin directions. Furthermore, spin-polarized band structures unveil a net magnetism in the range of 2.67µ B to 4.02µ B , highlighting the potential for spintronics applications. Finally, we investigate the thermodynamic properties using the quasi-harmonic model, where heat capacities at constant pressure and volume, entropy, Debye temperature, and thermal expansion coefficient are analyzed and discussed under both pressure and temperature effects. Overall our study provides a comprehensive understanding of the multifaceted properties of Delafossites, paving the way for their potential applications in various fields.

Isostatic pressure effects on the elastic and electronic properties of non-doped and Mn4+-doped K2SiF6 (KSF) have been investigated by first-principles calculations within density functional theory (DFT). Bulk modulus was obtained by the Murnaghan’s equation of states (EOS) using the relationship between volume and pressures at pressures between 0 and 40 GPa, and elastic constants were calculated by the stress–strain relationship giving small distortions at each pressure point. The other elastic parameters such as shear modulus, sound velocity and Debye temperature, which can be obtained from the elastic constants, were also estimated. The influence of external isostatic pressure on the electronic properties, such as crystal field strength 10Dq and emission energy of 2E → 4A2 transition (Eem), of KSF:Mn4+ was also studied. The results suggest that 10Dq and Eem linearly increase and decrease, respectively, with increasing pressure.

We build the melting theory and the theory of the Debye temperature for defective and perfect cubic metals mainly based on the statistical moment method. Our theoretical results are applied to metals Ni, Pd and Pt. Our calculations of melting temperatures agree well with experiments and other calculations. Our other calculations are highly reliable.

Novel zinc-blende (zb) group-IV binary XC and ternary XxY1−xC alloys (X, Y ≡ Si, Ge, and Sn) have recently gained scientific and technological interest as promising alternatives to silicon for high-temperature, high-power optoelectronics, gas sensing and photovoltaic applications. Despite numerous efforts made to simulate the structural, electronic, and dynamical properties of binary materials, no vibrational and/or thermodynamic studies exist for the ternary alloys. By adopting a realistic rigid-ion-model (RIM), we have reported methodical calculations to comprehend the lattice dynamics and thermodynamic traits of both binary and ternary compounds. With appropriate interatomic force constants (IFCs) of XC at ambient pressure, the study of phonon dispersions ωjq→ offered positive values of acoustic modes in the entire Brillouin zone (BZ)—implying their structural stability. For XxY1−xC, we have used Green’s function (GF) theory in the virtual crystal approximation to calculate composition x, dependent ωjq→ and one phonon density of states gω. With no additional IFCs, the RIM GF approach has provided complete ωjq→ in the crystallographic directions for both optical and acoustical phonon branches. In quasi-harmonic approximation, the theory predicted thermodynamic characteristics (e.g., Debye temperature ΘD(T) and specific heat Cv(T)) for XxY1−xC alloys. Unlike SiC, the GeC, SnC and GexSn1−xC materials have exhibited weak IFCs with low [high] values of ΘD(T) [Cv(T)]. We feel that the latter materials may not be suitable as fuel-cladding layers in nuclear reactors and high-temperature applications. However, the XC and XxY1−xC can still be used to design multi-quantum well or superlattice-based micro-/nano devices for different strategic and civilian application needs.

The local atomic structure of the non-magnetic layered superconductor Bi4O4S3 was investigated using neutron diffraction and pair density function (PDF) analysis. Although on average, the crystal structure is well ordered, evidence for local, out–of–plane sulfur distortions is provided, which may act as a conduit for charge transfer from the SO4 blocks into the superconducting BiS2 planes. In contrast with LaO1−xFxBiS2, no sulfur distortions were detected in the planes, which indicates that charge density wave fluctuations are not supported in Bi4O4S3.

Understanding thermal transport across metal/semiconductor interfaces is crucial for the heat dissipation of electronics. The dominant heat carriers in non-metals, phonons, are thought to transport elastically across most interfaces, except for a few extreme cases where the two materials that formed the interface are highly dissimilar with a large difference in Debye temperature. In this work, we show that even for two materials with similar Debye temperatures (Al/Si, Al/GaN), a substantial portion of phonons will transport inelastically across their interfaces at high temperatures, significantly enhancing interface thermal conductance. Moreover, we find that interface sharpness strongly affects phonon transport process. For atomically sharp interfaces, phonons are allowed to transport inelastically and interface thermal conductance linearly increases at high temperatures. With a diffuse interface, inelastic phonon transport diminishes. Our results provide new insights on phonon transport across interfaces and open up opportunities for engineering interface thermal conductance specifically for materials of relevance to microelectronics. Phonons are thought to transport elastically across most interfaces. Here, the authors show that a substantial portion of phonons transport inelastically, adding another heat conduction channel and enhancing thermal conductance across interfaces.

The coefficient of thermal expansion of a solid can be derived from (1) anharmonicity of atomic vibrations; (2) lattice dynamics; (3) equation of state by G. Mie; (4) equation of state by E. Grüneisen; and (6) potential of interatomic interaction. Only the last theory in this list provides us with the equation describing correctly all features in the thermal expansion: (1) proportionality between thermal expansion and heat capacity; (2) various values of “plateau” for the coefficient of thermal expansion at temperatures close to Debye temperature; and (3) acceleration of the thermal expansion in the vicinity of melting point.