THEORETICAL BASIS AND GENERAL APPLICABILITY OF THE COUPLING MODEL TO RELAXATIONS IN COUPLED SYSTEMS

The coupling model proposed more than a decade ago for the description of relaxations in complex correlated systems by one of us (KLN) have been shown repeatedly to be applicable to amorphous polymers, viscous liquids, the glassy state, metallic glasses, glassy ionic conductors a nd etc. In these examples, the relaxing species are dense packed and m utually interacting. As a consequence, the constraints between them ha ve a strong influence on the relaxation dynamics. Very recent quasiela stic neutron scattering experimental data as well as molecular dynamic s simulation results which provide dramatic proof of the validity of t he coupling model will be discussed. The applicability of the coupling model to some relaxations in metals including precipitates and the Sn oek-Koster relaxation is less obvious but has recently been proposed, justified and demonstrated to be relevant by one of us (YNW). The appl icability of the coupling model to these and other problems of immedia te interest to participants of ICIFUAS-10 will be summarized and discu ssed. For Snoek-Koster relaxation, additional experimental data in ult ra-high purity iron containing low concentration of carbon obtained by one of us (LBM) show characteristics that cannot be explained by Seeg er's model of thermally activated formation of kink pairs on screw dis locations in the presence of foreign interstitial atoms, but are consi stent with the coupling model.