Lattice dynamics of skutterudites: Inelastic x-ray scattering on $\mathrm{Co}{\mathrm{Sb}}_3$

Skutterudite based materials are important for thermoelectric applications. In order to be able to tune the thermoelectric properties, it is necessary to understand the mechanism of thermal conductivity, which, in turn, is strongly influenced by the lattice dynamics. The lattice dynamics of the skutterudite parent compound $\mathrm{Co}{\mathrm{Sb}}_3$ have been investigated by inelastic x-ray scattering experiments on single crystals. The experimental results are compared to predictions of different lattice dynamical calculations. The best description of the dispersion of the normal modes in the skutterudite lattice is obtained on the basis of an ab initio approach.

Figure 1

(Color online) Spectra at the H point in comparison with the results of the ab initio LDA calculation (this work), the FS-model D (Ref. 4), and the LK model (Ref. 1).

Figure 2

(Color online) Phonon dispersion along [001]: experimentally observed longitudinal (full circles) and transversal (full diamonds) modes and computed by ab initio calculations (full lines). At the $\Gamma$ point, experimental data are taken from infrared (open circles and diamonds for longitudinal and transversal modes, respectively) and Raman (open triangles) spectroscopy as reported in Refs. 1, 2, 3. First derivatives of acoustic branches at the zone center as obtained from ab initio elastic constant calculations are indicated by dashed lines.

Figure 3

(Color online) Phonon dispersion along a path through the bcc Brillouin zone (left panel) and total and atom-projected phonon densities of states (PDOS) (right panel) as calculated from first principles.