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Debye model
About: Debye model is a research topic. Over the lifetime, 7462 publications have been published within this topic receiving 133987 citations.
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TL;DR: In this article, x-ray diffraction and X-ray absorption spectroscopy (XAS) at room temperature and at elevated temperatures below and above the glass transition temperature was used to examine the phenomena that occur during glass transition.
Abstract: The metallic glass Zr65Al7.5Cu27.5 exhibits a wide temperature range in the undercooled liquid region. This offers the possibility of examining the phenomena that occur during glass transition. We investigated this glass by x-ray diffraction and x-ray absorption spectroscopy (XAS) at room temperature and at elevated temperatures below and above the glass transition temperature. The total number of nearest neighbors determined by x-ray diffraction remained unchanged. Using XAS irreversible changes in the short range order (SRO) towards the SRO of crystalline Zr2Cu is observed in the nearest neighbor shell which is consistent with the x-ray diffraction results. The long range order was not affected by these changes. From the temperature dependence of the atomic mean-square relative displacements σ2, Debye temperatures were determined and they compare well with low temperature specific heat measurements. Above Tg the slope of σ2 increases drastically and is attributed to anharmonic effects.
37 citations
TL;DR: In this paper, the dependences of the structural, thermodynamic, elastic, and magnetic properties of Cr2GeC on pressure and temperature were investigated with the quasiharmonic Debye model and the first-principles method based on the density functional theory.
Abstract: The dependences of the structural, thermodynamic, elastic, and magnetic properties of Cr2GeC on pressure and temperature were investigated with the quasiharmonic Debye model and the first-principles method based on the density functional theory. Our calculated data, which were obtained at different pressures and temperatures, are in good agreement with the experimental results. Cr2GeC is mechanically stable in the pressure range of 0–50 GPa and the compressibility along the a axis is greater than along the c axis indicating that the presence of C in the interstitial sites of the Cr octahedra can enhance the stability of the Cr–Ge bonds. It is also found that the antiferromagnetic state is the ground state of Cr2GeC and the total induced magnetic moment of the metastable ferromagnetic state decreases with pressure and completely vanishes at about 25 GPa.
37 citations
TL;DR: In this article, Ho 3+ substituted cobalt-zinc ferrite with a chemical formula Co 0.7 Zn 0.3 Ho x Fe 2−x O 4 (0≤x≤0.1) were synthesized by sol-gel method.
37 citations
TL;DR: In this article, the temperature dependence of the energy gap EG and the binding energy Rx of free excitons in single crystals of CuInTe2 have been calculated using Elliot's model.
Abstract: The temperature dependence of the energy gap EG and the binding energy Rx of free excitons in single crystals of CuInTe2 have been calculated using Elliot’s model. The samples were prepared by the method of tellurization of stoichiometric Cu and In in liquid phase and the vertical Bridgman technique. The value of Rx around 4 meV agrees quite well with that deduced from the effective mass approximation. The variation of EG with temperature is compared with the empirical model proposed by A. Mannogian and J. C. Woolley [Can. J. Phys. 62, 285 (1984)]. The estimated value of the Debye temperature is in agreement with ΘD=191.4 K reported from specific heat measurements.
37 citations
TL;DR: In this paper, the structural, electronic, optical and thermodynamic properties of Mo2Ga2C were investigated using density functional theory (DFT) within the generalized gradient approximation (GGA).
Abstract: The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density functional theory (DFT) within the generalized gradient approximation (GGA). The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. The electronic density of states (DOS) is calculated and analyzed. The metallic behavior for the compound is confirmed and the value of DOS at Fermi level is 4.2 states per unit cell per eV. Technologically important optical parameters (e.g., dielectric function, refractive index, absorption coefficient, photo conductivity, reflectivity, and loss function) are calculated for the first time. The study of dielectric constant (ɛ 1) indicates the Drude-like behavior. The absorption and conductivity spectra suggest that the compound is metallic. The reflectance spectrum shows that this compound has the potential to be used as a solar reflector. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient of Mo2Ga2C MAX phase are derived from the quasi-harmonic Debye model with phononic effect also for the first time. Analysis of T c expression using available parameter values (DOS, Debye temperature, atomic mass, etc.) suggests that the compound is less likely to be superconductor.
37 citations