Thermal expansion and crystal structure of FeSi between 4 and 1173 K determined by time-of-flight neutron powder diffraction

Vočadlo, Lidunka; Knight, K. S.; Price, G. D.; Wood, Ian G.

doi:10.1007/s002690100202

Cited by 122 publications

(121 citation statements)

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“…This corresponds roughly to a temperature of 500 K according to the measured data in Ref. 25 and is slightly higher to what was estimated in Ref. 8 By comparison, the ZPM from the same data corresponds to displacements of about 0.006a 0 .…”

Section: Methods Of Calculationmentioning

confidence: 82%

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Importance of thermal disorder and electronic occupation for temperature dependence of optical conductivity in FeSi and MnSi

Jarlborg

2007

Phys. Rev. B

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The spectral weight ͑SW͒ for optical transitions in FeSi and MnSi are calculated as a function of temperature by means of linear muffin-tin orbital-local density approximation band calculations. The main effects, caused by structural disorder and electronic Fermi-Dirac distribution, act oppositely on the T dependence of the SW, while the variation of the magnetic moment in MnSi has only a minor effect. The calculations agree with the experimental findings of an increasing SW in FeSi and a decreasing SW in MnSi as function of T. The results can be understood from the change of the band structure with disorder.

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Section: Methods Of Calculationmentioning

confidence: 82%

“…However, the atomic masses are not too different and ͗u Fe 2 ͘ and ͗u Si 2 ͘ are comparable. 25 Moreover, the electronic structure is such that Si displacements are of minor importance, since the dominant d-DOS comes from the transition metal.…”

Section: Methods Of Calculationmentioning

confidence: 99%

Importance of thermal disorder and electronic occupation for temperature dependence of optical conductivity in FeSi and MnSi

Jarlborg

2007

Phys. Rev. B

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“…We also calculated the QH softening for FeSi using the experimental Grüneisen parameter reported in ref. 24. The measured phonon softening in FeSi deviates strongly from the QH behavior.…”

Section: Anomalous Phonon Softeningmentioning

confidence: 91%

“…2B, where it is compared to the QH behavior. The expected phonon softening in the QH approximation was calculated using experimental thermal expansion data (10,24), and the Grüneisen parameters we obtained from first-principles calculations, γðFeSiÞ ¼ 1.61, γðCoSiÞ ¼ 1.73. We also calculated the QH softening for FeSi using the experimental Grüneisen parameter reported in ref.…”

Section: Anomalous Phonon Softeningmentioning

confidence: 99%

Phonon softening and metallization of a narrow-gap semiconductor by thermal disorder

Delaire

Marty

Stone

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

105

109

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The vibrations of ions in solids at finite temperature depend on interatomic force-constants that result from electrostatic interactions between ions, and the response of the electron density to atomic displacements. At high temperatures, vibration amplitudes are substantial, and electronic states are affected, thus modifying the screening properties of the electron density. By combining inelastic neutron scattering measurements of Fe 1−x Co x Si as a function of temperature, and finite-temperature first-principles calculations including thermal disorder effects, we show that the coupling between phonons and electronic structure results in an anomalous temperature dependence of phonons. The strong concomitant renormalization of the electronic structure induces the semiconductor-to-metal transition that occurs with increasing temperature in FeSi. Our results show that for systems with rapidly changing electronic densities of states at the Fermi level, there are likely to be significant phonon-electron interactions, resulting in anomalous temperature-dependent properties.electron-phonon coupling | metal-insulator transition | thermoelectrics B ecause many properties of the solid state derive from the electronic structure (1), understanding finite temperature effects on the band structure is crucial to accurately describe materials in realistic operating conditions. The effects of thermal disorder on the electronic structure of materials at high temperature are largely unexplored, however, and the role of the electron-phonon interaction above room temperature has remained controversial (2-5). We performed detailed investigations of the phonons and electronic structure in Fe 1−x Co x Si and found that an adiabatic coupling can lead to pronounced anomalies in the temperature dependence of both phonons and electron states. The mechanism is general and could affect a broad class of materials, including narrow-gap semiconductors, superconductors, heavy-Fermion compounds, and thermoelectrics.FeSi has attracted a great deal of interest as it exhibits an insulator-metal transition with increasing temperature, and many of its physical properties show anomalous temperature dependences, including the magnetic susceptibility, heat capacity, Seebeck coefficient, thermal expansion, and elastic properties (6-11). Recently, it has been argued that doping FeSi with Al can lead to a surprising heavy-Fermion metal (12). FeSi has also attracted attention as a possible reaction product at Earth's core-mantle boundary (13-16), and as a candidate thermoelectric material for refrigeration applications (9). The compounds FeSi and CoSi are isostructural, crystallizing in the cubic B20 structure, with similar ion coordinates (17, 18). Although FeSi undergoes a gradual transition from narrow-gap semiconductor (E gap ∼ 0.1 eV) to metal with increasing temperature, the additional d electron in CoSi leads to a metallic state at all temperatures. The anomalous temperature dependences observed in FeSi are absent in CoSi.Here, we show that the adia...

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“…4(b)] and suggests a loss of magnetism around 92 A 3 , in contrast to our observations. ZPM motion of atoms exists and it has been measured in FeSi [29], with a mean deviation of 0.03 Å , for T ! 0.…”

Section: Prl 98 047204 (2007) P H Y S I C a L R E V I E W L E T T E mentioning

confidence: 99%

Metallic State in Cubic FeGe Beyond Its Quantum Phase Transition

et al. 2007

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We report on results of electrical resistivity and structural investigations on the cubic modification of FeGe under high pressure. The long-wavelength helical order (T C 280 K) is suppressed at a critical pressure p c 19 GPa. An anomaly at T X p and strong deviations from a Fermi-liquid behavior in a wide pressure range above p c suggest that the suppression of T C disagrees with the standard notion of a quantum critical phase transition. The metallic ground state persisting at high pressure can be described by band-structure calculations if zero-point motion is included. The shortest FeGe interatomic distance display discontinuous changes in the pressure dependence close to the T C p phase line.

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Thermal expansion and crystal structure of FeSi between 4 and 1173 K determined by time-of-flight neutron powder diffraction

Cited by 122 publications

References 0 publications

Importance of thermal disorder and electronic occupation for temperature dependence of optical conductivity in FeSi and MnSi

Importance of thermal disorder and electronic occupation for temperature dependence of optical conductivity in FeSi and MnSi

Phonon softening and metallization of a narrow-gap semiconductor by thermal disorder

Metallic State in Cubic FeGe Beyond Its Quantum Phase Transition

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