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					STRUCTURAL RELAXATION AND VISCOSITY BEHAVIOR IN SELENIUM SUPERCOOLED MELT
Jiří Málek (1), Roman Svoboda (1), Petr Koštál (1)
(1) Department of Physical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573,
Pardubice 532 10, Czech Republic
jiri.malek@upce.cz

Volume and enthalpy relaxation studies have been performed in selenium supercooled melt by mercury dilatometry [1] and
differential scanning calorimetry [2]. For simple temperature jump experiments, as well as for more complex thermal history
the volume and enthalpy relaxation data can be described by a single set of kinetic parameters for Tool-Naraynaswamy-
Moynihan (TNM) model and for Adam-Gibbs-Scherer (AGS) model. The times required to reach equilibrium for volume and
enthalpy relaxation do not seem to differ significantly, within the limit of experimental uncertainty. A self-consistent data
evaluation shows that at moderate departure from equilibrium volume and enthalpy in amorphous selenium relax in the same
way as expressed by TNM and AGS models. Both volume and enthalpy change can be interpreted within the same fictive
temperature concept [3].
          New measurements of viscosity of selenium melt are reported as well as previously published data from numerous
authors which allow to fit the Adam-Gibbs (AG) and the Vogel-Fulcher-Tamman (VFT) equations with viscosities ranging
from 10-1 to 1014 Pa.s. The similarity between the preexponential factor of AG and VFT has been confirmed. The activation
energy of viscous flow in the glass transition range is identical with the effective activation energy for the structural
relaxation process as determined by TNM model. Extensive collection of experimental data allows a detailed discussion of
studied phenomena.

[1] R. Svoboda, P. Pustková, J. Málek, J. Non-Cryst. Solids 352 (2006) 4793.
[2] R. Svoboda, P. Pustková, J. Málek, J. Phys. Chem. Solids 68 (2007) 850.
[3] J. Málek, R. Svoboda, P. Pustková, P. Čičmanec, J. Non-Cryst. Solids 355 (2009) 264.

Financial support for this research from the Czech Science Foundation under grant No. 104/08/1021 is acknowledged.

				
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