Phonon dispersion relations for potassium thiocyanate at and above room temperature

The elastic stiffness constants of KSCN have been measured using a pulse-echo-overlap method at 10 MHz and compared to those for CsSCN. In both crystals it was found that transverse waves propagating normal to the minor planes encountered the greatest shear stiffness. Room temperature inelastic neutron scattering has been used to measure phonon energies of less than 5 THz in KSCN at various positions in reciprocal space. At higher temperatures the acoustic phonon resonances were found to soften gradually, while the optic modes exhibited largely unpredictable changes in width, frequency and intensity.