6533b7dbfe1ef96bd126fe8a

RESEARCH PRODUCT

Dynamic anomaly in the glass transition region of orthoterphenyl

Eckhard BartschB. FaragoF. FujaraM. KiebelWinfried PetryHans Sillescu

subject

Stretched exponential functionPhysicsCondensed matter physicsNeutron scatteringCondensed Matter PhysicsPower lawElectronic Optical and Magnetic Materialssymbols.namesakeSpin echosymbolsRelaxation (physics)General Materials ScienceAnomaly (physics)Debye–Waller factorvan der Waals force

description

We report on incoherent and coherent neutron scattering results in the supercooled liquid and the glassy regime of the van der Waals fluido-terphenyl using the backscattering and spin echo technique, respectively. A critical comparison of both techniques is presented. The data are analysed in the time domain assuming that microscopic correlation times (τ) scale with the viscosity η according to τ(T)∼η(T)/T. With this assumption we obtain an agreement with several predictions of mode coupling theory: the existence of a critical temperatureT c is shown, independently for both incoherent and coherent data, by a cusp in the temperature dependence of the Debye-Waller factorf Q (T). BelowT c fQ(T) follows the predicted $$\sqrt {T_c - T} $$ behaviour yielding also theQ-dependence of the critical parametersf Q c andh Q . AboveT c the α-process or structural relaxation can be well parametrized by a stretched exponential function. In accordance with theory the structural relaxation curves can also be described by a power law with a critical (von Schweidler) exponentb=0.525±0.10.

https://doi.org/10.1007/bf01309415