Tension effect in local dynamics of cuprite structures

摘要

Cuprite crystals, Cu_2O and Ag_2O, display a negative thermal expansion in a wide temperature range. This work shows, through a phenomenological approach, how the next-nearest-neighbors dynamics observed by EXAFS in both crystals [A. Sanson, E Rocca, G. Dalba, P. Fornasini, R. Grisenti, M. Daptaggi, G. Artioli, Phys. Rev. B 73 (2006), 214305] is directly connected to a tension mechanism. As a result, the negative thermal expansion in cuprite crystals could be described within the Rigid Unit Modes formalism, but replacing the typical rigid polyhedral units by rigid rods between nearest-neighbors atoms.