Topic
Debye model
About: Debye model is a research topic. Over the lifetime, 7462 publications have been published within this topic receiving 133987 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, it was shown that the low-temperature elastic constants of vitreous silica can account for only a small fraction of the lowtemperature heat capacity.
122 citations
TL;DR: In this paper, the hydrodynamic velocity υϕ along the path of constant crystallographic structure was approximated by the formula ∂ ln υ ϕ/∂ lns ρ = − ½[1−(∂ln VM/∆ ln A)]−1, where ρ is the density and VM is the molar volume.
Abstract: Simple approximations for the lattice vibrational spectrum allow the regularities of velocity-density plots with structure and composition to be semiquantitatively explained from a simple and unified point of view. It is possible to explicitly separate paths of constant mean atomic weight A where velocities change because of compression or phase changes from paths of constant crystallographic structure where the mean atomic weight is changed. One can approximate the hydrodynamic velocity υϕ along the path of constant crystallographic structure by the formula ∂ ln υϕ/∂ ln ρ = − ½[1−(∂ ln VM/∂ ln A)]−1, where ρ is the density and VM is the molar volume.
122 citations
TL;DR: In this paper, the authors reported the successful replacement of B by C in the series MgB2−xCx for values of x upto 0.3 is reported.
Abstract: Successful replacement of B by C in the series MgB2−xCx for values of x upto 0.3 is reported. Resistivity and ac susceptibility measurements have been carried out in the samples. Solubility of carbon, inferred from the observed change in the lattice parameter with carbon content indicates that carbon substitutes upto x=0.30 into the MgB2 lattice. The superconducting transition temperature, Tc measured both by zero resistivity and the onset of the diamagnetic signal shows a systematic decrease with increase in carbon content upto x=0.30, beyond which the volume fraction decreases drastically. The temperature dependence of resistivity in the normal state fits to the Bloch–Gruneisen formula for all the carbon compositions studied. The Debye temperature, θD, extracted from the fit, is seen to decrease with carbon content from 900 to 525 K, whereas the electron–phonon interaction parameter, λ, obtained from the McMillan equation using the measured Tc and θD, is seen to increase monotonically from 0.8 in MgB2 to 0.9 in the x=0.50 sample. The ratio of the resistivities between 300 and 40 K versus Tc is seen to follow the Testardi correlation for the C substituted samples. The decrease in Tc is argued to mainly arise due to large decrease in θD with C concentration and a decrease in the hole density of states at N(EF).
121 citations
TL;DR: In this article, the size-dependences of the melting point, Debye temperature, thermal expansion coefficient, and specific heat of nanostructured materials have been modeled free of adjustable parameters.
Abstract: The size-dependences of the melting point, Debye temperature, thermal expansion coefficient, and the specific heat of nanostructured materials have been modeled free of adjustable parameters. The melting point and Debye temperature drop while the thermal expansion coefficient and specific heat rise when the grain size is decreased. Relative to nanoparticles, however, the variation of the above parameters of nanostructured material is weak, dominated by the ratio of the grain boundary energy to the surface energy. Our theoretical predictions agree fairly well with available experimental and computer simulation results for semiconductors and metals.
121 citations
TL;DR: There is a strong correlation between lattice dynamics and an ultralow thermal conductivity for series CsSnBr3-xIx reaching 0.32 Wm-1K-1 at 550 K and the crystallography data and theoretical calculations suggest the Cs atom deviates from its ideal cuboctahedral geometry imposed by the perovskite cage and behaves as a heavy atom rattling oscillator.
Abstract: Halide perovskites are anticipated to impact next generation high performance solar cells because of their extraordinary charge transport and optoelectronic properties. However, their thermal transport behavior has received limited attention. In this work, we studied the thermal transport and thermoelectric properties of the CsSnBr3-xIx perovskites. We find a strong correlation between lattice dynamics and an ultralow thermal conductivity for series CsSnBr3-xIx reaching 0.32 Wm-1K-1 at 550 K. The CsSnBr3-xIx also possess a decent Seebeck coefficient and controllable electrical transport properties. The crystallography data and theoretical calculations suggest the Cs atom deviates from its ideal cuboctahedral geometry imposed by the perovskite cage and behaves as a heavy atom rattling oscillator. This off-center tendency of Cs, together with the distortion of SnX6 (X = Br or I) octahedra, produces a highly dynamic and disordered structure in CsSnBr3-xIx, which gives rise to a very low Debye temperature and phonon velocity. Moreover, the low temperature heat capacity data suggests strong coupling between the low frequency optical phonons and heat carrying acoustical phonons. This induces strong phonon resonance scattering that induces the ultralow lattice thermal conductivity of CsSnBr3-xIx.
121 citations