Mode Grüneisen parameter dispersion relation of RbI determined by neutron scattering

Abstract

Inelastic-neutron-scattering measurements of 43 mode Gr\"uneisen parameters for the [$00\ensuremath{\xi}$], [$\ensuremath{\xi}\ensuremath{\xi}0$], and [$\ensuremath{\xi}\ensuremath{\xi}\ensuremath{\xi}$] directions of RbI are reported. These "mode $\ensuremath{\gamma}$'s" were determined to an accuracy of 2 to 10% of the Gr\"uneisen-parameter range (about -2 to +3). Comparison is made and good agreement is found with the results obtained using a breathing shell model which was extended to include the third-order anharmonic interactions. The third-order parameters including those due to electronic polarization effects are determined.