J. Phys. IV France
Volume 129, October 2005
Page(s) 45 - 49

J. Phys. IV France 129 (2005) 45-49

DOI: 10.1051/jp4:2005129010

The generalized Cauchy relation as an universal property of the amorphous state

J.K. Krüger1, 2, U. Müller1, 2, R. Bactavatchalou1, 2, J. Mainka1, 2, Ch. Gilow1, 2, W. Possart1, 2, A. Tschöpe1, 3, P. Alnot1, 4, D. Rouxel1, 4, R. Sanctuary1, 5 and B. Wetzel6

1  Laboratoire Européen de Recherche Universitaire : Saarland-Lorraine
2  Fachrichtung 7.2, Experimentalphysik, Universität des Saarlandes, Bau 38, 66041 Saarbrücken, Germany
3  Technische Physik - Gebäude 43B, Universität des Saarlandes, Postfach 15 11 50, 66041 Saarbrücken, Germany
4  Laboratoire de Physique des Milieux Ionisés et Applications, CNRS-UMR 7040, Université Henri Poincaré, 54506 Nancy I, France
5  Laboratoire de Physique des Matériaux, Université du Luxembourg-Limpertsberg, 1511 Luxembourg
6  Institut für Verbundwerkstoffe, TU Kaiserslautern, 67663 Kaiserslautern, Germany

From the structural point of view a simple Cauchy relation is not expected to hold for isotropic materials. Such a Cauchy relation would imply the reduction of independent elastic stiffness constants for the isotropic state from two to one. However, high frequency elastic data of glasses and viscous liquids show a linear transformation between the shear and the longitudinal elastic stiffness which is called a generalized Cauchy relation. It seems, that the parameters of the linear transformation are related to the global and local symmetry and/or order. Brillouin investigations on the elastic stiffness coefficients of a consolidated nano-crystalline material (CeO2) and of DGEBA/SiO2 nano-composites are used in order to elucidated the role of the discrepancy between local and global symmetry and/or order.

© EDP Sciences 2005