LATTICE VIBRATIONAL PROPERTIES OF URANIUM CHALCOGENIDES

Lattice vibrational properties of uranium chalcogenides (UX) (X = S, S e, Te) have been investigated by using the breathing shell model (BSM) which includes breathing motion of the electrons of the U-atom due to f-d hybridization. The phonon dispersion curves of UX compounds, calc ulated from the present model, agree with the measured data. A compari son has been made between the present and previously reported three-bo dy force rigid ion model (TRIM) by us [Phys. Rev. B 46 (1992) 3664]. T his reveals that the short-range breathing phenomena play a dominant r ole in the phonon properties of UX compounds. We also report, for the first time, the two phonon density of states and specific heats of the se compounds.