The Coupling Scheme for Relaxations in Complex Correlated Systems

  • K. L. Ngai
Part of the NATO ASI Series book series (NSSB, volume 258)


In this NATO Advanced Study Institute many different problems of large-scale molecular systems were discussed. The range of topics covered in this ASI is immensely broad. In view of the very nature of this ASI, what I addressed in lecture and elaborated further here is only a subset of all the large-scale molecular systems discussed in the Proceedings. I am primarily concerned with irreversible processes (relaxation) in correlated systems in which some identical constituents, molecules, ions, or their analogues, are interacting in either the quantum or classical mechanical sense, whichever is appropriate. Additional randomness caused by possible factors such as the presence of not identical constituents and fluctuations of local environments makes the problem even more complex. Correlated systems with additional complications such as distribution and randomness will be referred to as complex correlated systems. I am interested in the dynamics of irreversible processes in these systems which require solutions to these many body problems that give the time developments of either macroscopic (e.g. stress, strain, and electric polarization) or microscopic (e.g. orientation of tagged molecules, center-of-mass vector of a probe polymer chain in a polymer matrix) dynamical variables. When interactions between the constituents are strong, the system becomes highly correlated and solution is extremely difficult. In this paper I shall focus on three examples of such highly correlated systems. These are: (1) a glass forming viscous liquid that is made up of molecular units that are densely packed together and hence interacting strongly with each other (e.g. (O-terphenyl, 1,3,5 trinaphthalbenzene, and toulouene); (2) a vitreous ionic conductor (e.g. the alkali oxide trisilicate and triborate glasses, Na2O-3SiO2 and Li2O-3B2O3 respectively and also defect crystalline ionic conductors (e.g. Na β-alumina) that contain a propensity of interacting ions; and (3) polymer melts of long linear or star branched macromolecules that are fully entangled with each other and noncrossability of these densely packed macromolecules implies strong interaction.


Relaxation Function Coupling Scheme Continuous Time Random Walk Entangle Polymer NATO Advance Study Institute 
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Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • K. L. Ngai
    • 1
  1. 1.Naval Research LaboratoryUSA

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