Lattice dynamics of the filled skutterudite CeOs₄Sb₁₂

Inelastic neutron scattering was performed on both poly- and single-crystalline samples to study the lattice dynamics of the Ce-filled antimonide skutterudite. For powder samples, no well-defined extra phonon excitation peak, which was reported to indicate a local Einstein oscillating mode, was detected in the low-energy region of the vibrational density of states within the experimental accuracy. However, a coherent phonon was clearly observed in single crystals at different temperatures. The dispersion curves were measured along two symmetry axes[0 1 1] and [1 0 0] at room temperature and compared with theoretical calculation by Feldman [Phys. Rev. B 73, 014306 (2006)] using the model of local density approximation.