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Thermodynamics, dynamics and relaxation in glass‐forming liquids ‐ the conformon concept
Author(s) -
Kilian HannsGeorg,
Beyer Claus,
Pietralla Martin
Publication year - 1995
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19950900104
Subject(s) - supercooling , glass transition , thermodynamics , relaxation (psychology) , physics , excited state , boltzmann constant , condensed matter physics , statistical physics , materials science , quantum mechanics , nuclear magnetic resonance , psychology , social psychology , polymer
Any interpretation of the dynamics in liquids requires understanding of fluctuating collective motions in the stationary limit. To this end, “eigen‐states” are defined, named conformons . Conformons are to be considered as a new type of bosons. Their properties characterize the typical features of the dynamics in disordered systems. Eigen‐energy and “eigen‐entropy” are adjusted to each other to minimize the free energy of each mode (saturation). The whole conformon ensemble exhibits a photon statistics with a broad universal mode spectrum. Analogues of Stefan‐Boltzmann's law and of Wien's displacements law are formulated. A crucial point of our treatment is that conformons should, in principle, only become excited above a system‐typical temperature T o (Vogel‐Fulcher temperature). Equilibrium properties of supercooled liquids are necessarily related to T o . C p /C v , of the conformon ensemble should, for example, show a typical ΔT 3 ‐dependence (ΔT=T‐T o ). Experimental data give evidence in support of this behaviour. As a consequence of the excluded volume supercooled liquids already solidify about 30 to 40 degrees above T o at least at the quasi‐static glass temperature T g . Relaxation in the glass transition regime of glass formers can fully be described if relaxation modes are connected to each conformon. The description covers a set of experiments so different like mechanical and dielectric relaxation or quasi‐elastic light‐ and neutron scattering.