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 and etc. In these examples, the relaxing species are dense packed and mutually interacting. As a consequence, the constraints between them have a strong influence on the relaxation dynamics. Very recent quasielastic neutron scattering experimental data as well as molecular dynamics simulation results which provide dramatic proof of the validity of the coupling model will be discussed. The applicability of the coupling model to some relaxations in metals including precipitates and the Snoek-Koster relaxation is less obvious but has recently been proposed, justified and demonstrated to be relevant by one of us (YNW). The applicability of the coupling model to these and other problems of immediate interest to participants of ICIFUAS-10 will be summarized and discussed. For Snoek-Koster relaxation, additional experimental data in ultra-high purity iron containing low concentration of carbon obtained by one of us (LBM) show characteristics that cannot be explained by Seeger's model of thermally activated formation of kink pairs on screw dislocations in the presence of foreign interstitial atoms, but are consistent with the coupling model.