EXAFS studies of negative thermal expansion materials

Extended X-ray absorption fine structure (EXAFS) can give information on the local dynamical behavior of crystals, opening new perspectives for understanding the origin of negative thermal expansion (NTE). In this paper, after a short review on the effects of thermal. disorder in EXAFS spectra and on the relation between EXAFS and Bragg diffraction, some recent results on crystals with the zincblende and cuprite structures are presented and critically compared. The tension effect giving rise to NTE can be correlated to the anisotropy of the mean square relative displacements measured by EXAFS.