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Xinfeng Tang - One of the best experts on this subject based on the ideXlab platform.
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origin of intrinsically low thermal conductivity in talnakhite cu17 6fe17 6s32 thermoelectric material correlations between Lattice Dynamics and thermal transport
Journal of the American Chemical Society, 2019Co-Authors: Xianli Su, Xiaomi Zhang, Trevor P Bailey, Constantinos C Stoumpos, Alexios P Douvalis, Xiaobing Hu, Chris Wolverton, Vinayak P Dravid, Ctirad Uher, Xinfeng TangAbstract:Understanding the nature of phonon transport in solids and the underlying mechanism linking Lattice Dynamics and thermal conductivity is important in many fields, including the development of efficient thermoelectric materials where a low Lattice thermal conductivity is required. Herein, we choose the pair of synthetic chalcopyrite CuFeS2 and talnakhite Cu17.6Fe17.6S32 compounds, which possess the same elements and very similar crystal structures but very different phonon transport, as contrasting examples to study the influence of Lattice Dynamics and chemical bonding on the thermal transport properties. Chemically, talnakhite derives from chalcopyrite by inserting extra Cu and Fe atoms in the chalcopyrite Lattice. The CuFeS2 compound has a Lattice thermal conductivity of 2.37 W m–1 K–1 at 625 K, while Cu17.6Fe17.6S32 features Cu/Fe disorder and possesses an extremely low Lattice thermal conductivity of merely 0.6 W m–1 K–1 at 625 K, approaching the amorphous limit κmin. Low-temperature heat capacity mea...
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origin of intrinsically low thermal conductivity in talnakhite cu17 6fe17 6s32 thermoelectric material correlations between Lattice Dynamics and thermal transport
Journal of the American Chemical Society, 2019Co-Authors: Hongyao Xie, Xiaomi Zhang, Trevor P Bailey, Constantinos C Stoumpos, Alexios P Douvalis, Chris Wolverton, Vinayak P Dravid, Ctirad Uher, Shiqiang Hao, Xinfeng TangAbstract:Understanding the nature of phonon transport in solids and the underlying mechanism linking Lattice Dynamics and thermal conductivity is important in many fields, including the development of efficient thermoelectric materials where a low Lattice thermal conductivity is required. Herein, we choose the pair of synthetic chalcopyrite CuFeS2 and talnakhite Cu17.6Fe17.6S32 compounds, which possess the same elements and very similar crystal structures but very different phonon transport, as contrasting examples to study the influence of Lattice Dynamics and chemical bonding on the thermal transport properties. Chemically, talnakhite derives from chalcopyrite by inserting extra Cu and Fe atoms in the chalcopyrite Lattice. The CuFeS2 compound has a Lattice thermal conductivity of 2.37 W m-1 K-1 at 625 K, while Cu17.6Fe17.6S32 features Cu/Fe disorder and possesses an extremely low Lattice thermal conductivity of merely 0.6 W m-1 K-1 at 625 K, approaching the amorphous limit κmin. Low-temperature heat capacity measurements and phonon calculations point to a large anharmonicity and low Debye temperature in Cu17.6Fe17.6S32, originating from weaker chemical bonds. Moreover, Mossbauer spectroscopy suggests that the state of Fe atoms in Cu17.6Fe17.6S32 is partially disordered, which induces the enhanced alloy scattering. All of the above peculiar features, absent in CuFeS2, contribute to the extremely low Lattice thermal conductivity of the Cu17.6Fe17.6S32 compound.
S. L. Chaplot - One of the best experts on this subject based on the ideXlab platform.
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anomalous Lattice Dynamics in agc4n3 insights from inelastic neutron scattering and density functional calculations
Frontiers in Chemistry, 2018Co-Authors: Baltej Singh, S. L. Chaplot, Mayanak K Gupta, R Mittal, Mohamed Zbiri, Sarah A Hodgson, Andrew L Goodwin, Helmut SchoberAbstract:We have performed temperature dependent inelastic neutron scattering measurements to study the anharmonicity of phonon spectra of AgC4N3. The analysis and interpretation of the experimental spectra is done using ab-initio Lattice Dynamics calculations. The calculated phonon spectrum over the entire Brillion zone is used to derive linear thermal expansion coefficients. The effect of van der Waals interaction on structure stability has been investigated using advanced density functional methods. The calculated isothermal equation of states implies a negative linear compressibility along the c-axis of the crystal, which also leads to a negative thermal expansion along this direction. The role of elastic properties inducing the observed anomalous Lattice behaviour is discussed.
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inelastic neutron scattering and Lattice Dynamics perspectives and challenges in mineral physics
naee, 2009Co-Authors: Narayani Choudhury, S. L. ChaplotAbstract:An understanding of the fundamental physics of the Earth's interior requires information about the phase transitions and thermodynamic properties of key mantle-forming mineral phases. Inelastic neutron scattering (INS) is an indispensable tool for determining key Lattice Dynamics properties like the phonon dispersion relation (PDR) and density of states, which govern a wide range of material behaviors including structural phase transitions, thermodynamic properties, elasticity, and melting. In this chapter we review recent reported studies involving INS and Lattice Dynamics calculations of geophysically important minerals. We also review recent applications of INS involving experimental and theoretical ab initio and atomistic studies of the phonon spectra and thermodynamic properties of minerals and of other novel phenomena like high-pressure phonon softening, structural phase transitions, pressure-induced amorphization, magnetic excitations, melting, etc. We discuss the current understanding of the dynamical behavior, thermodynamic properties, and phase transitions of key mantle components like the olivine and pyroxene end members forsterite and enstatite, the mineral zircon, important silica polymorphs, and magnesium oxide; recent results on water and ice; other complex silicates; hydrogen storage materials; etc. Inelastic neutron scattering and complementary techniques like inelastic X-ray scattering have been used to explore the high-pressure PDR and density of states of iron, diamond, and magnesium oxide; to study magnetic excitations; to estimate the magnetic contributions to thermodynamic properties; etc. The theoretical calculations enable fruitful microscopic interpretations of complex experimental data and provide an atomic-level understanding of vibrational and thermodynamic properties.
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modeling of anomalous thermodynamic properties using Lattice Dynamics and inelastic neutron scattering
Progress in Materials Science, 2006Co-Authors: R Mittal, S. L. Chaplot, Niharendu ChoudhuryAbstract:Abstract This paper reviews some of the recent advances in the modeling of anomalous thermodynamic properties. Inelastic neutron scattering experiments in combination with Lattice Dynamics calculations are used to study the phonon properties as well as thermodynamic properties of several novel compounds. There is a large variation in the thermal expansion, specific heat and equation of state pertaining to the compounds described in this review. The interatomic potentials as determined for various compounds have been able to successfully model the thermodynamic behavior. Lattice dynamical calculations and high pressure inelastic neutron scattering experiments indicate that large softening of several low energy phonons is mainly responsible for the negative thermal expansion in ZrW2O8, HfW2O8 and ZrMo2O8 up to 1443, 1050 and 600 K, respectively. It has been shown that a proper description of negative thermal expansion requires consideration of both the acoustic and optic phonon modes in the entire Brillouin zone. We have also reviewed studies on X-ray image storage materials MFX (M = Ba, Pb, Sr; X = Cl, Br, I); compounds MPO4 (M = Al, Fe and Ga); several garnet minerals M3Al2Si3O12 (M = Fe, Mg, Ca and Mn) and zircon (ZrSiO4). The variations in phonon spectra manifest in the thermodynamic properties of these compounds at high pressure and temperature. The calculations enable predictions and microscopic interpretation of the thermal expansion, specific heat and the equation of state.
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Lattice Dynamics in rhodochrosite mnco3
Applied Physics A, 2002Co-Authors: Mala N Rao, Prabhatasree Goel, S. L. Chaplot, Subrata GhoseAbstract:Phonon-dispersion curves along the threefold axis and the phonon density of states of the external modes in rhodochrosite, MnCO3, have been measured by inelastic neutron scattering employing the triple-axis spectrometer at the Dhruva reactor, Trombay. Lattice-Dynamics computations based on a transferable potential model reveal the differences in the phonon properties of the isostructural minerals, calcite and rhodochrosite, and their manifestations in various thermodynamic quantities. The calculated dispersion curves and phonon density of states are in good agreement with experiments. The obtained results provide a strong experimental basis to validate the potential model.
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Lattice Dynamics and inelastic neutron scattering experiments on andalusite al2sio5
Solid State Communications, 2002Co-Authors: Prabhatasree Goel, Narayani Choudhury, S. L. Chaplot, Subrata GhoseAbstract:Abstract We report coherent inelastic neutron scattering measurements of the phonon dispersion relations and Lattice Dynamics shell model calculations of several microscopic and macroscopic properties of andalusite, Al 2 SiO 5 . Andalusite has an orthorhombic structure with 32 atoms/unit cell. The inelastic neutron scattering measurements (up to energy transfers of 45 meV) were carried out using the triple axis spectrometer at Dhruva reactor, India using a single crystal of andalusite and the phonon dispersion relations along the [100] direction have been measured. The shell model calculations have been used to compute the crystal structure, elastic constants, phonon frequencies, dispersion relations, density of states and the specific heat. The calculated results are in good agreement with available experimental data. The computed one-phonon neutron scattering structure factors based on the shell model have been very useful in the planning and analysis of the inelastic neutron scattering experiments.
Sergey Y Savrasov - One of the best experts on this subject based on the ideXlab platform.
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linear response theory and Lattice Dynamics a muffin tin orbital approach
Physical Review B, 1996Co-Authors: Sergey Y SavrasovAbstract:A detailed description of a method for calculating static linear-response functions in the problem of Lattice Dynamics is presented. The method is based on density functional theory and it uses linear muffin-tin orbitals as a basis for representing first-order corrections to the one-electron wave functions. As an application we calculate phonon dispersions in Si and NbC and find good agreement with experiments.
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linear response theory and Lattice Dynamics a muffin tin orbital approach
Physical Review B, 1996Co-Authors: Sergey Y SavrasovAbstract:A detailed description of a method for calculating static linear-response functions in the problem of Lattice Dynamics is presented. The method is based on density-functional theory and it uses linear muffin-tin orbitals as a basis for representing first-order corrections to the one-electron wave functions. This makes it possible to greatly facilitate the treatment of the materials with localized orbitals. We derive variationally accurate expressions for the dynamical matrix. We also show that large incomplete-basis-set corrections to the first-order changes in the wave functions exist and can be explicitly calculated. Some useful hints on the k-space integration for metals and the self-consistency problem at long wavelengths are also given. As a test application we calculate bulk phonon dispersions in Si and find good agreement between our results and experiments. As another application, we calculate Lattice Dynamics of the transition-metal carbide NbC. The theory reproduces the major anomalies found experimentally in its phonon dispersions. The theory also predicts an anomalous behavior of the lowest transverse acoustic mode along the (\ensuremath{\xi}\ensuremath{\xi}0) direction. Most of the calculated frequencies agree within a few percent with those measured. \textcopyright{} 1996 The American Physical Society.
Aron Walsh - One of the best experts on this subject based on the ideXlab platform.
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Lattice Dynamics of the tin sulphides sns2 sns and sn2s3 vibrational spectra and thermal transport
Physical Chemistry Chemical Physics, 2017Co-Authors: Jonathan M Skelton, Lee A Burton, Adam J Jackson, Fumiyasu Oba, Stephen C Parker, Aron WalshAbstract:We present an in-depth first-principles study of the Lattice Dynamics of the tin sulphides SnS2, Pnma and π-cubic SnS and Sn2S3. An analysis of the harmonic phonon dispersion and vibrational density of states reveals phonon bandgaps between low- and high-frequency modes consisting of Sn and S motion, respectively, and evidences a bond-strength hierarchy in the low-dimensional SnS2, Pnma SnS and Sn2S3 crystals. We model and perform a complete characterisation of the infrared and Raman spectra, including temperature-dependent anharmonic linewidths calculated using many-body perturbation theory. We illustrate how vibrational spectroscopy could be used to identify and characterise phase impurities in tin sulphide samples. The spectral linewidths are used to model the thermal transport, and the calculations indicate that the low-dimensional Sn2S3 has a very low Lattice thermal conductivity, potentially giving it superior performance to SnS as a candidate thermoelectric material.
Isao Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Prediction of Low-Thermal-Conductivity Compounds with First-Principles Anharmonic Lattice-Dynamics Calculations and Bayesian Optimization
Physical Review Letters, 2015Co-Authors: Atsuto Seko, Koji Tsuda, Laurent Chaput, Atsushi Togo, Hiroyuki Hayashi, Isao TanakaAbstract:Compounds of low Lattice thermal conductivity (LTC) are essential for seeking thermoelectric materials with high conversion efficiency. Some strategies have been used to decrease LTC. However, such trials have yielded successes only within a limited exploration space. Here we report the virtual screening of a library containing 54,779 compounds. Our strategy is to search the library through Bayesian optimization using for the initial data the LTC obtained from first-principles anharmonic Lattice Dynamics calculations for a set of 101 compounds. We discovered 221 materials with very low LTC. Two of them have even an electronic band gap < 1 eV, what makes them exceptional candidates for thermoelectric applications. In addition to those newly discovered thermoelectric materials, the present strategy is believed to be powerful for many other applications in which chemistry of materials are required to be optimized.
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Lattice Dynamics and thermal properties of srhfo3 by first principles calculations
Physica Status Solidi B-basic Solid State Physics, 2009Co-Authors: Hidenobu Murata, Hiroki Moriwake, Tomoyuki Yamamoto, Isao TanakaAbstract:First-principles Lattice Dynamics calculations are systematically made on four polymorphs of SrHfO3. The hierarchy of the total energy at the ground state is Pmm > I4/mcm > Cmcm > Pnma, which agrees with the sequence of iterative transitions with temperature as reported by experiments. Three structures, Pmm, I4/mcm and Cmcm, are found to be dynamically unstable at the ground state. A soft mode of phonons appears in I4/mcm and Cmcm at the Γ-point. The atomic displacements for the soft mode are analogous to those of the R25 mode of Pmm, which is related to the rotation of the HfO6 octahedron. Pnma phase shows lowest energy and it is the only dynamically stable structure among the four phases. The volume expansion coefficient, bulk modulus and heat capacity are computed within quasi-harmonic approximations using the vibrational density of states. They are compared to experimental data. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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ab initio Lattice Dynamics and phase transformations of zro2
Physical Review B, 2005Co-Authors: Akihide Kuwabara, Tetsuya Tohei, Tomoyuki Yamamoto, Isao TanakaAbstract:Zirconia, $\mathrm{Zr}{\mathrm{O}}_{2}$, is one of the most important ceramic materials in modern technology. Its versatility is closely related to phase transformations. Although the transformations have been repeatedly investigated by experiments, fundamental aspects of the transformations are still under debate. In the present paper, we have made first principles calculations to study the Lattice Dynamics of $\mathrm{Zr}{\mathrm{O}}_{2}$ polymorphs and phase transformation at finite temperatures. Cubic phase shows a soft mode at the $X$ point in the Brillouin zone, which should spontaneously induce cubic-to-tetragonal transformation. In tetragonal and monoclinic $\mathrm{Zr}{\mathrm{O}}_{2}$, all vibrational modes have real frequency. Calculations of Helmholtz free energies show that the tetragonal phase becomes more stable than the monoclinic phase above $1350\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, which is in quantitative agreement with experimental results. This confirms that vibrational entropy contributes to destabilize monoclinic $\mathrm{Zr}{\mathrm{O}}_{2}$ at elevated temperatures.