Bulg. J. Phys. vol.32 no.4 (2005), pp. 302-309

Transformation of Activated Hopping into Free Diffusion Dynamics in the Glass-Forming Liquids

H. A. Solunov
University of Plovdiv Paissi Hilendarski, 4000 Plovdiv, Bulgaria
Abstract. A method for measuring transformation of the activated hopping over potential barriers dynamics into free diffusion one in the glass-forming liquid has been found. In the glass-forming liquids the rearrangement of a local molecular structure is a cooperative process and the number of rearranging molecular species during the time of relaxation is defined as the size of the cooperatively rearranging region. At the glass-transition temperature every molecular species in the cooperatively rearranging region overcomes its own potential barrier and the number of the configurations per a basic molecular species is approximately equal to one, so the dynamics is assumed to be entirely activated. The increase of the number of configurations per a basic molecular species with increasing the temperature is applied as a measure for the transformation of the activated dynamics. Strong correlation of the level of transformation and the fragility of the liquid is observed.

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