Abnormal temperature-dependent variation in sound velocity for the molecular liquids benzene and hexafluorobenzene

Letamendia, L.; Belkadi, M.; Eloutassi, Omar; Vaucamps, C.; Nouchi, G.; Iakovlev, S.; Rozhdestvenskaya, N. B.; Smirnova, L. V.; Runova, J. E.

doi:10.1103/physreve.48.3572

Cited by 8 publications

(5 citation statements)

References 16 publications

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“…Our experimental Brillouin shift values fall on a straight line within the experimental error when plotted as a function of temperature (see Figure ), and the velocity data do the same (see Figure ). In addition, our values of the Brillouin frequencies for benzene agree within 1.5% with the results of ref , after correction for different values of the exchanged wave vector (see Figure ). Thus, we also see no indication of the anomalous behavior reported previously.…”

Section: Discussionsupporting

confidence: 89%

“…25 A few years ago, some experimental results were reported that suggested the presence of a relaxation process or a structural transition involving different local arrangements of the molecules in liquid benzene. [28][29][30] In particular, the observation of anomalous temperature behaviors observed both by Brillouin 30 and depolarized light scattering 31 were interpreted on the basis of a competition among different orientational packing arrangements, taking place over a narrow temperature range (27-50 °C).…”

Section: Discussionmentioning

confidence: 99%

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Evidences of Nonideal Mixing in Poly(ethylene Glycol)/Organic Solvent Mixtures by Brillouin Scattering

et al. 2005

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The concentration dependence of the hypersonic properties of solutions of poly(ethylene glycol) of mean molecular mass 600 g/mol (PEG600) in benzene and toluene has been investigated by Brillouin scattering. The two solvents are very similar in structure and chemical properties, but while benzene is nonpolar, toluene possess a modest dipole. In both solvents a high-frequency relaxation process has been observed at high concentrations which has been assigned to conformational rearrangements of the polymeric chains, triggered by reorientation of the side groups. In both cases, the concentration dependence of the adiabatic compressibility deviates significantly from linearity, indicating the existence of nonideal mixing phenomena driven by aggregation processes taking place in the systems. However, there is no temperature dependence for solutions of PEG600 in benzene; on the contrary, the results obtained for solutions of PEG600 in toluene are noticeably dependent on the temperature. The comparison of the experimental data with the results of previous experiments on similar systems allows a general picture for weakly interacting mixtures of hydrogen-bonded systems and organic solvents to be developed. In particular, in the presence of a nonpolar solvent molecule the local structure of the mixture is dominated by solute self-association processes and any resulting solute-solvent correlation is barely induced by excluded volume effects. At high enough dilution the self-aggregation of solute molecules produces a variety of new local topologies that cannot be observed in bulk solute, and as a consequence, the concentration evolution of the system is too rich to be described in terms of a linear combination of a few components over the whole concentration range. The situation seems to be simpler for the polar toluene solvent molecules, where a three-component model seems able to fit the experimental concentration dependence of the hypersonic velocity. This result is interpreted to imply that the interaction between the solvent dipoles and the active sites of the solute produces a relatively stable heterocoordination, while the relevance of self-association is partially reduced.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Evidences of Nonideal Mixing in Poly(ethylene Glycol)/Organic Solvent Mixtures by Brillouin Scattering

et al. 2005

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“…Although Rayleigh−Brillouin light scattering is a spectroscopic technique that is sensitive to collective motions that produce density fluctuations, there is a strong correlation between microscopic local properties and hydrodynamic modes. As well as it was observed in other molecular liquids, this correlation allows the effects of single-molecule reorientation and conformational rearrangement to be followed, thus suggesting the microscopic origin for the temperature behavior of macroscopic quantities (viscosity, density, etc.) in pure liquids.…”

Section: Discussionsupporting

confidence: 64%

Structural Properties of 1-Octanol/n-Octane Mixtures Studied by Brillouin Scattering

et al. 2003

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Polarized Rayleigh-Brillouin spectra of 1-octanol/n-octane solutions at different mole fractions have been recorded in the temperature range of 5-70 °C by using a 90°scattering configuration. Hypersonic velocities and acoustic attenuations have been calculated by means of a fitting procedure with suitable Lorentzian functions. The relaxation of the liquid structure revealed by viscous and thermal energy losses has been interpreted and discussed in terms of a local H-bond network and conformational modifications. The thermal behavior of macroscopic parameters such as number density and shear viscosity has also been studied in the same temperature range in an effort to better interpret the observed relaxation processes and the distribution of their relaxation times.

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“…Abnormal temperature dependence of molecular liquids properties have also been reported. For example, anomalies in the depolarized light scattering of benzene and hexafluorobenzene have been reported and have been explained by a probable structural change [6,7].Temperature dependence measurements of sound velocity have revealed a clear change at about 308 K and 314 K in liquid benzene as well as at about 309 K and 319 K in hexafluorobenzene [8]. However, neutron diffraction and molecular-dynamics (MD) simulation of liquid benzene and hexafluorobenzene [9] and high-resolution stimulated Brillouin gain spectroscopy of liquid benzene [10] have not found evidence of structural transition.…”

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confidence: 99%

Molecular simulation of unusual dynamical properties of quinoline in liquid phase

Millot¹,

Soetens

Ahmad

et al. 2011

EPL

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Molecular-dynamics simulations of liquid quinoline between 276 and 320 K and liquid isoquinoline between 300 and 365 K have been done using a simple effective atom-atom potential. The translational diffusion coefficient of quinoline is found to present a small non-Arrhenius behavior. Rotational diffusion coefficients, second-order reorientational correlation times of the CH vectors and T1 13 C NMR relaxation times of quinoline reproduce the non-Arrhenius break around 290 K observed experimentally for quinoline by different experimental techniques. Isoquinoline seems to present a non-Arrhenius behavior, too, though with less clear break temperatures. Such behaviors are correlated with a smooth continuous evolution of the structure at dimer level.

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Abnormal temperature-dependent variation in sound velocity for the molecular liquids benzene and hexafluorobenzene

Cited by 8 publications

References 16 publications

Evidences of Nonideal Mixing in Poly(ethylene Glycol)/Organic Solvent Mixtures by Brillouin Scattering

Evidences of Nonideal Mixing in Poly(ethylene Glycol)/Organic Solvent Mixtures by Brillouin Scattering

Structural Properties of 1-Octanol/n-Octane Mixtures Studied by Brillouin Scattering

Molecular simulation of unusual dynamical properties of quinoline in liquid phase

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