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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, self-diffusion coefficients for fcc Ni are obtained as a function of temperature by first-principles calculations based on density functional theory within the local density approximation.

40 citations

Journal ArticleDOI
TL;DR: In this article, first principles pseudopotential calculations have been performed for the first time to investigate the phonon dispersion, thermodynamic and optical properties including charge density, Fermi surface, Mulliken population analysis, theoretical Vicker hardness of predicted MAX phase Sc2InC.
Abstract: First principles pseudopotential calculations have been performed for the first time to investigate the phonon dispersion, thermodynamic and optical properties including charge density, Fermi surface, Mulliken population analysis, theoretical Vickers hardness of predicted MAX phase Sc2InC We revisited the structural, elastic and electronic properties of the compound which assessed the reliability of our calculations The analysis of the elastic constants and the phonon dispersion along with phonon density of states indicates the mechanical stability and dynamical stability of the MAX phase The Helmholtz free energy, internal energy, entropy specific heat capacity and Debye temperature have also been calculated from the phonon density of states Mulliken population analysis indicates the existence of prominent covalency in chemical bonding of Sc2InC The electronic charge density mapping shows a combination of ionic, covalent and metallic bonding in the compound The Fermi surface is comprised due to the low dispersive Sc 3d and C 2p states from the [ScC] blocks The phase is expected to be a soft material and easily mechinable due to its low Vicker hardness value Furthermore, the analysis of various optical properties (such as dielectric function, refractive index, photoconductivity, absorption coefficients, loss function and reflectivity) suggests that the nanolaminate Sc2InC is a promising candidate for optoelectronic devices in the visible and ultraviolet energy regions and as a coating material to avoid solar heating

40 citations

Journal ArticleDOI
TL;DR: In this article, the thermal diffusivity and thermal conductivity of single crystal (100) lanthanum aluminate (LaAlO3) have been determined in the temperature range 77-353 K.
Abstract: The thermal diffusivity and thermal conductivity of single crystal (100) lanthanum aluminate (LaAlO3) have been determined in the temperature range 77–353 K. The thermal diffusivity was measured using a transient heat‐pulse technique and the thermal conductivity by a steady state dc technique. The specific heat capacity was calculated from the thermal diffusivity and thermal conductivity data obtained. The temperature dependence of the thermal diffusivity was found to be of the form [T exp(TD/bdT)] and that of the thermal conductivity of the form [T3 exp(TD/bcT)]. Both results are consistent with the expected behavior of the thermal transport, limited by phonon‐phonon collision (‘‘Umklapp’’) processes, in high purity dielectric single crystals. The Debye temperature (TD) was calculated as 720±22 K and the parameters bd and bc were found to be 1.4±0.1 and 0.7±0.1, respectively. The average sound velocity was calculated to be (5.4±0.6)×105 cm/s. The phonon mean‐free‐path at 303 K was found to be (2.2±0.2)×1...

40 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that for different cubic crystal structures, such a law is only fulfilled within relatively large error limits, and the adequate moduli are Gh={c44[c44(c11−c12)/2]1/2} 1/2 and Gt=[c44c66(c 11−c 12)/2]-1/3] 1/3 for materials with hexagonal and tetragonal symmetry.
Abstract: In the literature a relation is often used that correlates Debye temperature and bulk modulus by a square‐root law. It was recently shown that, for different cubic crystal structures, such a law is only fulfilled within relatively large error limits. If one takes, however, the average of the elastic constants of the transversal acoustic phonon modes as elastic modulus instead of the bulk modulus, the square‐root law is established with high precision. It is demonstrated that the same procedure may also be applied successfully to materials with hexagonal crystal symmetry such as hexagonal close‐packed metals and semiconducting compounds with the wurtzite structure, and to different structures of the tetragonal system. The adequate moduli are Gh={c44[c44(c11−c12)/2]1/2} 1/2 and Gt=[c44c66(c11−c12)/2]1/3 for materials with hexagonal and tetragonal symmetry, respectively. The difference between the various structures of a crystal system is quantitatively described by the different number of atoms in the cryst...

40 citations

Journal ArticleDOI
09 Feb 1994
TL;DR: In this article, the authors analyzed the thermal expansion properties of synthetic orthopyroxenes (Fe 0.20Mg 0.80)SiO3, (Fe0.40Mg0.60) SiO3 and Fe 0.75Mg 1.17)Si O3 by means of singlecrystal x-ray diffraction in the temperature range from 296 to 1300 K.
Abstract: Thermal expansion properties of synthetic orthopyroxenes (Fe0.20Mg0.80)SiO3, (Fe0.40Mg0.60)SiO3, (Fe0.50Mg0.50)SiO3, (Fe0.75Mg0.25)SiO3 and (Fe0.83Mg0.17)SiO3 were systematically studied by means of single-crystal x-ray diffraction in the temperature range from 296 to 1300 K. The measurements of unit cell dimensions as a function of temperature reveal that the a and c dimensions and the unit cell volume V increase nonlinearly with a positive curvature with rising temperature, whereas the b dimension behaves differently, depending on the total Fe content. For Mg-rich orthopyroxenes (Fe/(Fe+Mg) 30%. Together with the high temperature neutron diffraction data on enstatite (MgSiO3) (McMullan, Haga and Ghose, unpublished) and x-ray diffraction data on ferrosilite (FeSiO3) (Sueno et al. 1976), the measured unit cell dimensions were analyzed in terms of the Gruneisen theory of thermal expansion. The linear thermal expansion coefficients α a and α c both increase as temperature is elevated, with α c increasing faster, while α b changes gradually from increasing for Mg-rich orthopyroxenes to decreasing for Fe-rich orthopyroxenes. The relative magnitudes of linear thermal expansion coefficients are always in the order α b >α c >α a between 300 and 500 K, but at higher temperatures, the order changes to α c >α b >α a for Mg-rich orthopyroxenes and α c >α a >α b for Fe-rich ones. The linear thermal expansion behavior is interpreted on the basis of the structural mechanical model of Weidner and Vaughan (1982). The anomalous behavior of α b is mainly attributed to the changes in the Fe2+ population at the M2 site and the relative stiffness of the M2(Fe2+)-O bonds compared to the M2(Mg2+)-O bonds. The volume thermal expansion coefficients are nonlinear functions of temperature and lie between 23 and 49×10−6/K. The previously reported results of mean volume thermal expansion coefficients appear to represent the α V values characteristic of higher temperatures compared to our results. The thermal Debye temperatures are composition-dependent, decreasing linearly from 812 (MgSiO3) to 561 K (FeSiO3), and are systematically higher than the corresponding acoustic Debye temperatures. The Gruneisen parameters range from 0.85 to 0.89 and do not seem to vary with composition. The linear compressibilities derived from thermal expansion and elastic moduli data agree very well. The pressure derivatives of the isothermal bulk modulus (dK0/dP) are also composition-dependent and decrease from 11.2 (MgSiO3) to 8.77 (FeSiO3). Such large values indicate possible anomalous elastic behavior of orthopyroxenes at high pressures in the Earth's upper mantle.

40 citations


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