Signatures of the glass transition in a van der Waals liquid seen by neutrons and NMR

Bartsch, E.; Fujara, F.; Geil, Burkhard; Kiebel, M.; Petry, W.; Schnauss, W.; Sillescu, H.; Wuttke, Joachim

doi:10.1016/0378-4371(93)90418-4

Cited by 28 publications

(9 citation statements)

References 26 publications

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“…The existence and the importance of the dynamic transition temperature T c were supported by a number of experimental results [56][57][58], including the anomalous behavior in the Debye-Waller factor observed by scattering [59] and ultrasonic experiments [60] and also the change in the temperature dependence of viscosity around T c (see also Refs. [56,61]).…”

Section: Mode-coupling Theorymentioning

confidence: 94%

Two-order-parameter model of the liquid–glass transition. I. Relation between glass transition and crystallization

Tanaka

2005

Journal of Non-Crystalline Solids

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Section: Mode-coupling Theorymentioning

confidence: 94%

Two-order-parameter model of the liquid–glass transition. I. Relation between glass transition and crystallization

Tanaka

2005

Journal of Non-Crystalline Solids

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“…ortho-Terphenyl (OTP, C6H5C6H4C6H5, figure I), as one of the archetypal molecular glass formers, has been studied by different techniques like neutron diffraction [2, 31, light scattering 141, dielectric relaxation measurements [5] and NMR [3,6]. Criado et d. [7] measured and calculated the lattice spectrum of OTP, Perova et al [8] recorded the temperature dependence of the low frequency Raman and FIR spectra of crystalline and glassy OTP, and Kirin et al…”

Section: Introductionmentioning

confidence: 99%

Molecular vibrations and lattice dynamics of ortho-terphenyl

Baranović¹,

Bistričić

Volovšek

et al. 2001

Molecular Physics

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Infrared and Raman spectra of crystalline, melted and solvated orfho-terphenyl and its perdeuterated isotopomer, D14-ortho-tephenyl, have been recorded. Optimized geometries and vibrational frequencies were calculated by the semiempirical RHF/AM 1 method and by DFT using the B3LYP functional and 6-31G(d) basis set. In both cases the lowest energy conformation is of C2 symmetry. With the scaled AM1 and B3LYP/6-31G(d) force fields the average error in reproducing the experimental molecular vibrational frequencies is 13 cm-' and 5cm-*, respectively. The AM1 potential energy surface for phenyl torsions was mapped on a 15" grid. The barrier to concerted internal rotation is estimated to lie between 3 kJ mol-' and 6 kJmol-'. The calculations of the lattice dynamics at k = 0 in the low temperature fully ordered crystal phase of parent and deuterated ortho-terphenyl were performed with inclusion of six low lying intramolecular vibrations. The conformational change of the ortho-terphenyl molecule induced by crystal packing forces was taken into account by re-defining the unperturbed molecular vibrational state. Although an accurate assignment of lattice vibrations was not possible, the calculated spectra give quite a reasonable picture of the low frequency dynamics in crystalline ortho-terphenyl. The relevance of the results obtained to the glass forming property of ortho-terphenyl is discussed.The present study is an attempt to complete the assignment of the vibrational spectrum of OTP using both Raman and IR spectroscopy and to incorporate scaled semiempirical and DFT quantum mechanical calculations with subsequent use of these results in crystal dynamics calculations. Particularly interesting in the vibrational dynamics of OTP is the assignment of the low frequency intramolecular modes, and the evaluation of their possible role in the formation of the glassy state. There has been speculation in the literature about whether torsional motion of the side phenyl rings is responsible for the secondary relaxation in OTP. A secondary or ,&relaxation in the OTP glass was observed by dielectric relaxation [5] and by neutron diffraction 121. An important contribution in this respect is the molecular dynamics simulation study [lo], in which an empirical intramolecular torsional potential was used. A qualitative picture of the short-term dynamics in OTP has been achieved without, however, stating explicitly the extent to which side ring flips are responsible for the secondary, either fast or slow, relaxation. ExperimentalThe OTP sample was purchased from Aldrich and used without further purification. The sample of per-Molecular Physics ISSN 0026-8976 print/ISSN 1362-3028 online 0 2001 Taylor

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“…To our knowledge, this decoupling phenomenon was first clearly pointed out by Rössler, 203 and Fujara et al 193 Meanwhile it has been observed for many supercooled liquids. [192][193][194][195][196][197][198][199] It is also found with other glass-forming systems such as polymers. 204, 205 Stillinger and Hodgdon 206 have denoted this phenomenon as translation-rotation paradox.…”

Section: Supercooled Liquidsmentioning

confidence: 64%

“…We list here only studies which have gone beyond the routine limits of NMR self-diffusion experiments. For pure liquids such studies have, for example, yielded data for ortho-terphenyl, 193,194 propylene carbonate, 195 glycerol 196,197 as well as a for series of more complex liquids serving as model systems in studies of the glassy state. 196,198,199 Data are also available for aqueous solutions of saccharides 200,201 and of LiCl.…”

Section: Supercooled Liquidsmentioning

confidence: 99%