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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, first-principles calculations of the structure, elastic properties, lattice dynamics, and some thermodynamic properties of Mg2Si and mg2Ge compounds are reported.
98 citations
TL;DR: The distinct low-temperature dynamics observed in these two perovskites suggest qualitative differences in the interaction between the molecular cation and the surrounding inorganic framework, with potential implications for defect screening and device performance at ambient temperatures.
Abstract: Hybrid main group halide perovskites hold great technological promise in optoelectronic applications and present rich and complex evolution of structure and dynamics. Here we present low-temperature dielectric measurements and calorimetry of APbI3 [A = CH3NH3+, HC(NH2)2+] that suggest glassy behavior on cooling. In both compounds, the dielectric loss displays frequency-dependent peaks below 100 K characteristic of a glassy slowing of relaxation dynamics, with HC(NH2)2PbI3 exhibiting greater glass fragility. Consistent with quenched disorder, the low-temperature heat capacity of both perovskites deviates substantially from the ∼T3 acoustic phonon contribution predicted by the Debye model. We suggest that static disorder of the A-site molecular cation, potentially coupled to local distortions of the Pb–I sublattice, is responsible for these phenomena. The distinct low-temperature dynamics observed in these two perovskites suggest qualitative differences in the interaction between the molecular cation and th...
98 citations
TL;DR: In this paper, the heat capacity results of the twelve metals listed in Table I can be represented by the above equations to within 0.i0 cal/deg (g atom) between 20°K and 50°K.
96 citations
SIDI1
TL;DR: In this article, the structural, electronic, elastic and thermodynamic properties of LuX (X = N, Bi and Sb) based on rare earth into phases, Rocksalt (B1) and CsCl (B2) have been investigated using full-potential linearized muffin-tin orbital method (FP-LMTO) within density functional theory.
Abstract: The structural, electronic, elastic and thermodynamic properties of LuX (X = N, Bi and Sb) based on rare earth into phases, Rocksalt (B1) and CsCl (B2) have been investigated using full-potential linearized muffin-tin orbital method (FP-LMTO) within density functional theory. Local density approximation (LDA) for exchange-correlation potential and local spin density approximation (LSDA) are employed. The structural parameters as lattice parameters a0, bulk modulus B, its pressure derivate B’ and cut-off energy (Ec) within LDA and LSDA are presented. The elastic constants were derived from the stress–strain relation at 0 K. The thermodynamic properties for LuX using the quasi-harmonic Debye model are studied. The temperature and pressure variation of volume, bulk modulus, thermal expansion coefficient, heat capacities, Debye temperature and Gibbs free energy at different pressures (0–50 GPa) and temperatures (0–1600 K) are predicted. The calculated results are in accordance with other data.
96 citations
TL;DR: In this paper, the authors used Debye approximation to model the low temperature lattice thermal conductivity and found that the large strain field fluctuation introduced by the disordered Fe ions generates extra strong phonon scatterings for lowered lattice temperature.
Abstract: Polycrystalline samples with the composition of Cu _(1−x)Fe_(1+x)S_2 (x = 0, 0.01, 0.03, 0.05, 0.1) were synthesized by a melting-annealing-sintering process. X-ray powder diffraction reveals all the samples are phase pure. The backscattered electron image and X-ray map indicate that all elements are distributed homogeneously in the matrix. The measurements of Hall coefficient, electrical conductivity, and Seebeck coefficient show that Fe is an effective n-type dopant in CuFeS_2. The electron carrier concentration of Cu_(1−x)Fe_(1+x)S_2 is tuned within a wide range leading to optimized power factors. The lattice phonons are also strongly scattered by the substitution of Fe for Cu, leading to reduced thermal conductivity. We use Debye approximation to model the low temperature lattice thermal conductivity. It is found that the large strain field fluctuation introduced by the disordered Fe ions generates extra strong phonon scatterings for lowered lattice thermal conductivity.
96 citations