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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 paper, the phonon properties of two groups of rare-earth pyrochlores, Ln 2 Zr 2 O 7 (Ln = La, Nd, Sm, Gd) and Gd 2 T 2 O7 (T = Zr, Hf, Sn, Pb), employing density functional theory and quasi harmonic approximation were investigated.

51 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetic entropy of NiS 2 is shown to be smaller than that of a localized spin 1 and is in good agreement with that expected for the magnetic moment observed by neutron diffraction.
Abstract: Specific heats of FeS 2 -CoS 2 -NiS 2 Solid solutions and of Ni 0.95 Cu 0.05 S 2 have been measured from 10 K to 350 K. Debye temperatures, coefficients of electronic contribution γ, magnetic ordering temperatures, and magnetic entropies have been determined. The magnetic entropy of ferromagnetic Fe 1- x Co x S 2 is proportional to cobalt concentration and is 40% of that expected for a localized spin 1/2 per Co atom, suggesting an itinerant character of e g electrons. The magnetic entropy of NiS 2 is smaller than that of a localized spin 1 and is in good agreement with that expected for the magnetic moment observed by neutron diffraction. The magnetic entropy of antiferromagnetic Co 1- x Ni x S 2 Suggests that only Ni atoms have magnetic moment in Ni-rich phase. The density-of-states curve of e g band for NiS 2 has been constructed from γ values assuming a rigid band. The band width of lower half of e g band is 0.6 eV. The Debye temperature decreases monotonously from 605 K of FeS 2 to 455 K of NiS 2 .

51 citations

Journal ArticleDOI
TL;DR: Anomalous lattice dynamics and thermal behavior have been observed for ligand-free, size-, and shapeselected Pt nanoparticles supported on nanocrystalline -Al2O3 via extended x-ray absorption finest structure spectroscopy as mentioned in this paper.
Abstract: Anomalous lattice dynamics and thermal behavior have been observed for ligand-free, size-, and shapeselected Pt nanoparticles NPs supported on nanocrystalline -Al2O3 via extended x-ray absorption finestructure spectroscopy. Several major differences were observed for the NPs with respect to bulk Pt: i a contraction in the interatomic distances, ii a reduction in the dynamic temperature-dependent bond-length disorder and associated increase in the Debye temperature D, and iii an overall decrease in the bond-length expansion coefficient coupled with NP stiffening. The increase in the Debye temperature is explained in terms of the NP size, shape, support interactions, and adsorbate effects. For a similar average size, we observe a striking correlation between the shapes of the NPs and their D values.

51 citations

Journal ArticleDOI
TL;DR: In this paper, the elastic properties of layered thermoelectrics BiOCuSe and LaOcuSe were determined using first-principles density functional theory calculations.
Abstract: We determine the elastic properties of the layered thermoelectrics BiOCuSe and LaOCuSe using first-principles density functional theory calculations. To predict their stability, we calculate six distinct elastic constants, where all of them are positive, and suggest mechanically stable tetragonal crystals. As elastic properties relate to the nature and the strength of the chemical bond, the latter is analyzed by means of real-space descriptors, such as the electron localization function (ELF) and Bader charge. From elastic constants, a set of related properties, namely, bulk modulus, shear modulus, Young's modulus, sound velocity, Debye temperature, Gruneisen parameter, and thermal conductivity, are evaluated. Both materials are found to be ductile in nature and not brittle. We find BiOCuSe to have a smaller sound velocity and, hence, within the accuracy of the used Slack's model, a smaller thermal conductivity than LaOCuSe. Our calculations also reveal that the elastic properties and the related lattice thermal transport of both materials exhibit a much larger anisotropy than their electronic band properties that are known to be moderately anisotropic because of a moderate effective-electron-mass anisotropy. Finally, we determine the lattice dynamical properties, such as phonon dispersion, atomic displacement, and mode Gruneisen parameters, in order to correlate the elastic response, chemical bonding, and lattice dynamics.

51 citations

Journal ArticleDOI
TL;DR: In this article, it is shown that, with exception of the alkali metals, such a law is only poorly fulfilled for other cubic elements and compounds, and a relation is often used that correlates Debye temperature and bulk modulus (c 11 + 2c 12 )/3 by a square-root law.
Abstract: Sophisticated methods have been put forward in the literature to calculate Debye temperatures from the elastic constants C ik . As a simple alternative method for cubic crystals, a relation is often used that correlates Debye temperature and bulk modulus (c 11 + 2c 12 )/3 by a square-root law. It is shown that, with exception of the alkali metals, such a law is only poorly fulfilled for other cubic elements and compounds. If one takes, however, elastic moduli such as [c 44 (c 11 - c 12 ) (c 11 + c 12 + 2c 44 )] 1/3 or {c 44 [(c 11 - c 12 ) c 44 /2] 1/2 (c 11 - c 12 + c 44 )/3} 1/3 instead of the bulk modulus the square-root law is established for various cubic material classes. This procedure eventually allows to easily evaluate hitherto unknown Debye temperatures from the elastic constants with high precision.

51 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023178
2022346
2021303
2020242
2019285
2018304