Piezospectroscopy of the Raman spectrum of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-quartz

Briggs, R. J.; Ramdas, A. K.

doi:10.1103/physrevb.16.3815

Cited by 48 publications

(33 citation statements)

References 20 publications

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“…Calculations of the 7~r parameters is less easy because of the unknown concerning the variation of (6 vJc~P) with temperature. The pressure-induced shifts measured at 4 K (Briggs and Ramdas 1977) do not significantly differ from those of Hemley (1987) and Asell and Nicol (1968) at 300 K. This observation does not rule out a possible change in (9 v~/c3P) at higher temperatures. 71r parameters have been calculated by assuming (9 v~/c~P) independent of temperature, so that calculations provide only upper limit for the 7~r-Then, calculated 7~r depends only on the values of Kr and v~ at a given temperature.…”

Section: Anharmonic Parameters Calculationscontrasting

confidence: 63%

Test of the vibrational modelling for the ?-type transitions: Application to the ?-? quartz transition

Castex

Madon

1995

Phys Chem Minerals

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Abstract.Vibrational modelling is at the present time the only known way to predict the heat capacities of the Earth's mantle minerals at high-pressure and high-temperature. To test the validity of this method for 2-type transitions, we have applied it to the c~-fl quartz transition (T o = 846 +_ 1 K). Raman spectra of quartz were recorded up to 900 K. Measured frequency shifts of the c~-quartz Raman modes were then used in conjunction with available high-pressure Raman data to calculate intrinsic mode anharmonicity, through the parameter a i = (c~LnvJ c~T)v. Vibrational modelling of the heat capacity at constant volume, Cv, and at constant pressure, Cp, including anharmonic corrections deduced from the a~ parameters, are compared to experimental data. Taking into account the soft-mode associated to the ~-fl quartz transition, the model reproduces the excess of Cp related to the transition. Then, this study confirms that detecting a soft-mode from vibrational data allows one to predict 2-type transitions. However, when modelling the thermodynamic properties, the contribution of a soft-mode cannot be established from spectroscopic data. Therefore, one needs first to determine this contribution in order to predict the heat capacities of Earth's mantle minerals displaying 2-type transitions. In c~-quartz, this contribution has been determined as 0.007% of the total number of the optic modes in the model of the density of states.

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Section: Anharmonic Parameters Calculationscontrasting

confidence: 63%

Test of the vibrational modelling for the ?-type transitions: Application to the ?-? quartz transition

Castex

Madon

1995

Phys Chem Minerals

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“…The softening is in particular related to the tensile stress. The Raman shift of the E modes is a function of the strains and the phonon deformation potentials [12][13][14] Do E ¼ að xx þ yy Þ þ b zz þ gð xx À yy Þ (1) with e xx , e yy and e zz the normal strains in the plan and in the c-axis direction, respectively. a, b, g are the phonon deformation potential.…”

Section: Methodsmentioning

confidence: 99%

Piezoelectric measurements on BiFeO3 single crystal by Raman scattering

Rovillain

Cazayous

Sacuto

et al. 2009

Journal of Magnetism and Magnetic Materials

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“…Influence of pressure and temperature to anharmonicity 489 This procedure was first introduced to study the influence of a uniaxial stress on cubic crystals 61,62 and was extended to uniaxial crystals. 63,64 Instead of the term klm K iklm ε lm u k in Eqn 49, one expresses the strain Hamiltonian as V D ij V ij ε ij .…”

Section: Introduction Of Symmetrymentioning

confidence: 99%

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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Piezospectroscopy of the Raman spectrum ofα-quartz

Cited by 48 publications

References 20 publications

Test of the vibrational modelling for the ?-type transitions: Application to the ?-? quartz transition

Test of the vibrational modelling for the ?-type transitions: Application to the ?-? quartz transition

Piezoelectric measurements on BiFeO3 single crystal by Raman scattering

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

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