ABSTRACT STRUCTURE AND DYNAMICS OF INCOMMENSURATE COMPOSITES

T. Janssen and O. Radulescu*

ITP, University of Nijmegen, Nijmegen 6525ED, The Netherlands
* present address: Physics Dept. University of Leeds, U.K.

Incommensurate composites and their dynamics have in the past been studied on the basis of the Frenkel-Kontorova model. New classes of compounds where there is a substantial interaction between the subsystems require more sophisticated models. As example the double chain model (DCM) will be discussed. The DCM allows for an incommensurate ground state in which each subsystem is a modulated structure depending on the parameters in the model, the modulation function is smooth or discontinuous. The transition line which is the discommensuration line corresponds with onset of a gap in the phason spectrum. Only on one side of the transition line a zero-frequency sliding mode is present. The available experimental evidence will be reviewed.