Influence of pressure and temperature on phonons in molecular chalcogenides: Crystalline<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">As</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">S</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></m

Zallen, Richard; Slade, M. L.

doi:10.1103/physrevb.18.5775

Cited by 160 publications

(64 citation statements)

References 44 publications

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“…The variations of 7iT and 7w with the vibrational frequencies are also similar to those observed for forsterite (Chopelas 1990) and garnets (Gillet et al in press). For molecular crystals, 7iT varies regularly with the wavenumbers (Zallen and Slade 1978). In contrast, compounds with olivine and garnet structures exhibit greater parameters which correlate with the kind of motion.…”

Section: Spectroscopymentioning

confidence: 83%

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines

1992

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Section: Spectroscopymentioning

confidence: 83%

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines

1992

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“…Figure 2 shows the band position versus temperature of the two bands observed at 302 and 267 cm À1 at 8 K. Temperature-dependent shifts of vibrational bands are an indication of anharmonic behaviour. In general, the temperature shift of Raman bands in solids can be described by the following expression [13,14]:…”

Section: Methodsmentioning

confidence: 99%

“…However, we were not able to obtain a satisfactory fit of the experimental data using this expression. A more general expression of phonon-phonon creations and destructions is given by [14]:…”

Section: Methodsmentioning

confidence: 99%

Lattice anharmonicity and structural evolution of LiBH₄: an insight from Raman and X-ray diffraction experiments

Hagemann

Filinchuk²,

Chernyshov³

et al. 2009

Phase Transitions

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New in situ Raman and synchrotron X-ray diffraction data (between 300 and 400 K) in conjunction with separate temperature-dependent Raman data (between 7 and 400 K) are presented. The low-frequency Raman spectra show good agreement with theoretical values obtained previously using periodic DFT calculations. The temperature-dependent spectra reveal the presence of significant anharmonicity of librational modes neither predicted theoretically nor noted in previous experiments. The splitting of the internal deformation mode 2 (of E symmetry in the free ion) decreases continuously with increasing temperature, but drops abruptly at the first-order orthorhombic to hexagonal phase transition observed at 381 K. The temperature dependence of the linewidth of the internal deformation mode 2 reveals coupling to reorientational motions of the borohydride ion in the orthorhombic phase. The thermal evolution of both crystal structure and vibration frequencies agree with the phase diagram suggested by the Landau theory.

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“…7) is clearly divided into three separate segments with a first large gap between frequencies of (1) the intermolecular modes around 50 cm -1 and intramolecular modes at higher frequencies. The intramolecular modes above 100 cm -1 are divided by a second gap between the bond-bending modes at (2) 180-220 cm -1 and the bond-stretching modes at (3) 330-379 cm -1 (Zallen and Slade 1978). Intermolecular Raman bands in the latticephonon regime, around 50 cm -1 , show the most significant blue shift.…”

Section: Raman Spectramentioning

confidence: 97%

Crystal-structure properties and the molecular nature of hydrostatically compressed realgar

et al. 2012

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The structure of realgar, As 4 S 4 , and its evolution with pressure have been investigated employing in situ X-ray diffraction, optical absorption and vibrational spectroscopy on single-crystal samples in diamond-anvil cells. Compression under true hydrostatic conditions up to 5.40 GPa reveals equation-of-state parameters of V 0 = 799.4(2.4) Å 3 and K 0 = 10.5(0.4) GPa with K 0 0 = 8.7. The remarkably high compressibility can be attributed to a denser packing of the As 4 S 4 molecules with shortening of the intermolecular bonds of up to 12 %, while the As 4 S 4 molecules remain intact showing rigid-unit behaviour. From ambient pressure to 4.5 GPa, Raman spectra exhibit a strong blue shift of the Raman bands of the lattice-phonon regime of 24 cm -1 , whereas frequencies from intramolecular As-S stretching modes show negligible or no shifts at all. On pressurisation, realgar shows a continuous and reversible colour change from bright orange over deep red to black. Optical absorption spectroscopy shows a shift of the absorption edge from 2.30 to 1.81 eV up to 4.5 GPa, and DFT calculations show a corresponding reduction in the band gap. Synchrotron-based measurements on polycrystalline samples up to 45.5 GPa are indexed according to the monoclinic structure of realgar.

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Influence of pressure and temperature on phonons in molecular chalcogenides: CrystallineAs4S4

Cited by 160 publications

References 44 publications

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines

Lattice anharmonicity and structural evolution of LiBH₄: an insight from Raman and X-ray diffraction experiments

Crystal-structure properties and the molecular nature of hydrostatically compressed realgar

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Influence of pressure and temperature on phonons in molecular chalcogenides: CrystallineAs4S4

Cited by 160 publications

References 44 publications

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines

Lattice anharmonicity and structural evolution of LiBH4: an insight from Raman and X-ray diffraction experiments

Crystal-structure properties and the molecular nature of hydrostatically compressed realgar

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Product

Resources

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Lattice anharmonicity and structural evolution of LiBH₄: an insight from Raman and X-ray diffraction experiments