Eur. Phys. J. B 29, 385-398 (2002)
https://doi.org/10.1140/epjb/e2002-00322-7

Dynamics of modulated and composite aperiodic crystals

The signature of the inner polarization in the neutron coherent inelastic scattering

¹ Institut de Recherche Mathématique de Rennes, University of Rennes 1, Campus de Beaulieu, 35042 Rennes, France
² Institute of Theoretical Physics, Nijmegen University, Postbus 9010, 6500 GL Nijmegen, The Netherlands
³ Groupe Matière Condensée et Matériaux, University of Rennes 1, Campus de Beaulieu, 35042 Rennes, France
⁴ Laboratoire Léon Brillouin, CEA-CNRS-CE Saclay, 91191 Gif-sur-Yvette, France

Corresponding author: ^a Ovidiu.Radulescu@univ-rennes1.fr

Received: 9 June 2002
Published online: 14 October 2002

Abstract

We compare within an unifying formalism the dynamical properties of modulated and composite aperiodic (incommensurate) crystals. We discuss the concept of inner polarization and we define an inner polarization parameter β that distinguishes between different acoustic modes of aperiodic crystals. Although this concept has its limitations, we show that it can be used to extract valuable information from neutron coherent inelastic scattering experiments. Within certain conditions, the ratio between the dynamic and the static structure factors at various Bragg peaks depends only on β. We show how the knowledge of β for modes of an unknown structure can be used to decide whether the structure is composite or modulated. The same information can be used to predict scattered intensity within unexplored regions of the reciprocal space, being thus a guide for experiments.