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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, the transition phase of GaN from zincblende (ZB) structure to rocksalt structure (RS) is investigated by ab initio plane-wave pseudopotential density functional theory method, and the thermodynamic properties of the ZB and RS structures are obtained through the quasi-harmonic Debye model.

80 citations

Journal ArticleDOI
TL;DR: In this article, a single-crystal calcium oxide, CaO, is measured in the temperature range from 300 to 1200 K (1.8 times of the Debye temperature) by the resonant sphere technique (RST).
Abstract: The elastic moduli of a single-crystal calcium oxide, CaO, are measured in the temperature range from 300 to 1200 K (1.8 times of the Debye temperature) by the resonant sphere technique (RST). The lowest 18 modes are identified in the frequency range from 0.6 to 1.4 MHz for the vibrating spherical specimen, which is 5.6564 mm in diameter and 3.3493 g/cm3 in density at room temperature, and the resonant frequencies are traced as a function of temperature. The adiabatic elastic moduli are determined in the present temperature range from the observed frequencies by inversion calculations. Most of the elastic moduli, except forC 12 modulus, decrease as temperature increases. The temperature curves ofC s andC 44 moduli cross at 372 K. This means that the CaO specimen has an isotropic elasticity at the temperature. The temperature derivatives (∂C 11/∂T) P and (∂C s/∂T) P become slightly less negative with temperature increase and (∂C s /∂T) P and (∂C 44/∂T) P are almost constant. Combining the present elastic data with thermal expansion and specimen heat capacity data of CaO, we present the temperature dependence of thermodynamic parameters important in the studies of earth's interior.

80 citations

Journal ArticleDOI
TL;DR: Pulse-induced critical scattering (PICS) as mentioned in this paper is a fast technique for determining thermodynamic and kinetic parameters of polymer solutions, which can be used to determine spinodal and critical loci for the system polystyrenecyclohexane (PS-CH) about 10 times faster and more accurately than in recent work based on conventional light scattering equipment and on turbidimetry.
Abstract: Pulse-induced critical scattering (PICS) is a new, fast technique for determining thermodynamic and kinetic parameters of polymer solutions. Relative intensities of scattered laser light are measured over periods of seconds after a fast temperature step into the region of Debye critical opalescence. In the mode of operation using thermal pulses to progressively lower temperatures, the intensity pulse shape gives sensitive information on the fluctuation equilibrium and on the kinetics of phase separation with formation of emulsions of sub-wavelength particles, Spinodal and critical loci for the system polystyrenecyclohexane (PS–CH) are measured about 10 times faster and more accurately than in recent work based respectively on conventional light scattering equipment and on turbidimetry. The classical Debye theory of scattering near a critical point, or Scholte's extension to spinodal points, gives excellent semi-empirical extrapolations to spinodal temperatures T s . Though there are signs that the classical theory needs amendment in the sense of the generalized nonlinear theory of Fisher, Chu, and co-workers, this would generally give results on T s in close agreement with the simpler classical theory in the experimental range accessible to PICS. The effects of heterodispersity on the phase diagram are studied, comparing data by Scholte and new data by PICS on PS–CH. The evidence suggests that spinodal loci are governed mostly by M w (as suggested by recent theories). Marked secondary effects seem, however, to arise, not (as recently suggested) from M n , but from M z . Results obtained by the technique of approaching phase equilibrium from the heterogeneous side, using an emulsion carefully ‘seeded’ by a thermal step, suggest that supercooling is more serious in cloud-point determinations of dilute polymer solutions than hitherto thought. The formation of sub-wavelength droplets follows kinetics bearing more than formal resemblance to that for the nucleation and growth of spherulitic crystals in bulk.

80 citations

Journal ArticleDOI
TL;DR: In this paper, a quantum-mechanical variational technique is applied to an Einstein model of a solid, and the heats of sublimation and equations of state of solid Ne, A, Kr, and Xe are calculated at 0\ifmmode^\circ\else\textdegree\fi{}K.
Abstract: A quantum-mechanical variational technique is applied to an Einstein model of a solid, and the heats of sublimation and equations of state of solid Ne, A, Kr, and Xe are calculated at 0\ifmmode^\circ\else\textdegree\fi{}K. Mie-Lennard-Jones 6-12 potentials appropriate to the gas-phase data are used throughout, and the importance of quantum-mechanical effects is discussed; in general, good agreement with experiment is obtained. From the theoretical zero-point energies equivalent Debye temperatures, $\ensuremath{\theta}$, are calculated, and from the dependence of these $\ensuremath{\theta}$ on volume, Gr\"uneisen constants are computed in good agreement with experiment. Theoretical compressibility curves (at 0\ifmmode^\circ\else\textdegree\fi{}K) are presented, and compared with the available experimental data; in the case of Ne, the only substance for which high-pressure data are available, the agreement is rather good up to 20 k atmos.

79 citations

Journal ArticleDOI
TL;DR: The Young's and shear moduli of polycrystalline yttrium oxide, dysprosium oxide, holmium oxide and erbium oxide were determined at room temperature as a function of volume fraction porosity using the sonic resonance technique as mentioned in this paper.
Abstract: The Young's and shear moduli of polycrystalline yttrium oxide, dysprosium oxide, holmium oxide, and erbium oxide were determined at room temperature as a function of volume fraction porosity using the sonic resonance technique. Linear relations empirically described the data for Y2O3, Hr2O3, and Er2O3. The Young's and shear moduli data for Dy2O3 were empirically described by Hasselman's and Spriggs’equations, respectively. The empirical curves which best fit the data were compared to theoretical expressions and agreed closely with a modified form of Mackenzie's equation. Values for bulk modulus, Poisson's ratio, and the Debye temperature were computed for each oxide, and the bulk modulus-volume relation was determined and compared to that of other oxides.

79 citations


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