Lattice vibrations in La(Ce)Fe4Sb12 and CoSb3:: Inelastic neutron scattering and theory -: art. no. 014306

We present results of time-of-flight inelastic neutron scattering phonon density of states measurements on (La,Ce)(0.9)Fe4Sb12 and CoSb3 as well as of a detailed comparison with lattice dynamical models in the literature. The MARI experimental setup is replicated by a theory for scattering from a polycrystalline material. The model considered for the filled materials is a local density approximation (LDA) based short-range force constant model and those considered for CoSb3 are the LDA-based model with the La-related parameters removed and a semiempirical model. We show that the presence of La significantly affects the shape of the spectrum. We also conclude that upon filling the Sb intrasquare force constants are weakened and that the transition-metal Sb bonds are almost unchanged.