  First principles calculations are used to investigate electronic band
structure and vibrational spectra of pnictogen substituted ternary
skutterudites. We compare the results with the prototypical binary composition
CoSb$_3$ to identify the effects of substitutions on the Sb site, and evaluate
the potential of ternary skutterudites for thermoelectric applications.
Electronic transport coefficients are computed within the Boltzmann transport
formalism assuming a constant relaxation time, using a new methodology based on
maximally localized Wannier function interpolation. Our results point to a
large sensitivity of the electronic transport coefficients to carrier
concentration and to scattering mechanisms associated with the enhanced
polarity. The ionic character of the bonds is used to explain the detrimental
effect on the thermoelectric properties.
