Bond anharmonicities, Gruneisen parameters and pressure-induced frequency shifts

Sherman, W.F.

doi:10.1088/0022-3719/13/25/005

Cited by 74 publications

(36 citation statements)

References 21 publications

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“…The frequency shift and broadening of the intramolecular Raman modes observed experimentally at high pressure [ Fig. 2(a)] are widely observed for conjugated materials and are attributed to an increased force constant of the covalent bonds with pressure [10,16,26].…”

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confidence: 86%

Optical Spectroscopy of a Polyfluorene Copolymer at High Pressure: Intra- and Intermolecular Interactions

et al. 2007

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We present optical spectroscopy studies of the conjugated polymer poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) at high pressure. The photoluminescence spectrum of F8BT in a dilute solid-state solution in polystyrene redshifts by 320 meV over 7.4 GPa, while that of a F8BT thin film redshifts 460 meV over a comparable pressure range. We attribute the redshift in solution to intrachain pressure effects, principally conformational planarization. The additional contribution from interchain pi-electron interactions accounts for the larger redshift of thin films.

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confidence: 86%

Optical Spectroscopy of a Polyfluorene Copolymer at High Pressure: Intra- and Intermolecular Interactions

et al. 2007

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“…23 The anisotropic elastic properties of the solids may be the cause of such effects, as suggested by Sherman considering the case of anisotropic Se and Te crystals. 24 According to Sherman, the increasing temperature forces the layers further from each other. This process weakens and lengthens the interlayer bonds, whilst strengthening and shortening the intralayer bonds.…”

Section: Temperature Dependence Of Mode Wavenumbersmentioning

confidence: 99%

Anharmonic line shift and linewidth of the Raman modes in TlInS₂ layered crystals

Yuksek

Gasanly

Aydınlı

2003

J Raman Spectroscopy

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The temperature dependence of the unpolarized Raman spectra from TlInS 2 layered crystal was measured between 10 and 300 K. The analysis of the experimental data showed that the temperature dependences of wavenumbers and linewidths are well described by considering the contributions from thermal expansion and lattice anharmonicity. The purely anharmonic contribution (phonon-phonon coupling) was found to be due to three-phonon processes. This work demonstrates that the two Raman modes at 280.9 and 292.3 cm −1 exhibit changes toward high wavenumbers as the temperature is raised from 10 to 300 K.

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“…As written by Sherman and Wilkinson, 2,3 in a completely harmonic approximation, where the force constant operating between any two masses is truly a constant and independent of the distance between the masses, the application of pressure would cause no observable frequency shift effects at all. The same statement can be done about the effect of temperature.…”

Section: Introductionmentioning

confidence: 96%

Effect of pressure and temperature on Raman spectra of solids: anharmonicity

Lucazeau

2003

J Raman Spectroscopy

270

222

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This paper gives a brief review of the effect of temperature and pressure on Raman spectra. Anharmonicity, defined by the cubic, quartic and higher terms in the potential expansion, is shown to be responsible for various properties such as dilatation or for variations of wavenumber and half-width of Raman bands with temperature and pressure, or may be strongly involved in phase transitions. This contribution does not pretend to be an exhaustive review on the subject but aims to introduce some basic concepts in a tutorial way before showing how intricated are these manifestations of anharmonicity. Copyright INTRODUCTIONProperties of materials are dependent on temperature and pressure. All applied research consists in studying the temperature and pressure dependence of their physical properties with a view to preparing the material to exhibit the expected properties in specific conditions of thermal and mechanical stress environment. Basic research consists in relating micro/meso-structural properties with the other physical properties. These relations exist via coupling coefficients which are often defined by a linear relationship. The present review presents the relations which govern the temperature and pressure dependence of the usual spectral parameters such as wavenumber, half-width and intensity of Raman bands. We shall point out the nonlinearity, also defined as anharmonicity, of the corresponding relationships. A tutorial and brief presentation of anharmonic effects in solids can be found in Chapter 8 of Ref. 1. As written by Sherman and Wilkinson, 2,3 in a completely harmonic approximation, where the force constant operating between any two masses is truly a constant and independent of the distance between the masses, the application of pressure would cause no observable frequency shift effects at all. The same statement can be done about the effect of temperature. However, as it becomes evident in the present special issue, this is not verified experimentally.Ł Correspondence to: Guy Lucazeau, LEPMI, (CNRS UMR 5631), Institut National Polytechnique de Grenoble, BP 75, F-38402 St. Martin d'Hères, Cedex, France. E-mail: guy.lucazeau@lepmi.inpg.fr † In memory of Evangelos Anastassakis, who should have been solicited for writing a review paper on such a subject.One of the aims of this paper is to point out that the measurements of temperature-or pressure-induced frequency shifts are measurements of the anharmonicity of the interactions that supply the restoring force constants. Let us point out that because pressure or temperature induces isotropic or anisotropic deformations of molecules and crystals, the pressure or stress-induced and the temperatureinduced frequency shifts  / are mainly determined by the associated deformation V/V. It is thus important to analyze the effects of temperature and pressure together. The origin of the deformation induced by these two external parameters is different. Pressure affects the equilibrium spacings between nuclei, distorts the electron clouds and through them...

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Bond anharmonicities, Gruneisen parameters and pressure-induced frequency shifts

Cited by 74 publications

References 21 publications

Optical Spectroscopy of a Polyfluorene Copolymer at High Pressure: Intra- and Intermolecular Interactions

Optical Spectroscopy of a Polyfluorene Copolymer at High Pressure: Intra- and Intermolecular Interactions

Anharmonic line shift and linewidth of the Raman modes in TlInS₂ layered crystals

Effect of pressure and temperature on Raman spectra of solids: anharmonicity

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Bond anharmonicities, Gruneisen parameters and pressure-induced frequency shifts

Cited by 74 publications

References 21 publications

Optical Spectroscopy of a Polyfluorene Copolymer at High Pressure: Intra- and Intermolecular Interactions

Optical Spectroscopy of a Polyfluorene Copolymer at High Pressure: Intra- and Intermolecular Interactions

Anharmonic line shift and linewidth of the Raman modes in TlInS2 layered crystals

Effect of pressure and temperature on Raman spectra of solids: anharmonicity

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Anharmonic line shift and linewidth of the Raman modes in TlInS₂ layered crystals