  We have performed density functional calculations of the electronic structure
and lattice dynamics of the binary skutterudite FeSb$_{3}$. We find that the
ground state of FeSb$_{3}$ is a near semi-metallic ferromagnet with
$T_{c}=175$~K. Furthermore, we find that FeSb$_{3}$ is softer than CoSb$_{3}$
based on an analysis of the relation of the elastic constants and the shape of
the phonon density of states in the two systems, which is in agreement with
experimental observation. Based on these observations we find it plausible that
FeSb$_{3}$ will have a lower thermal conductivity than CoSb$_{3}$.
Additionally, our calculations indicate that FeSb$_{3}$ may be stable towards
decomposition into FeSb$_{2}$ and Sb. Furthermore, for ferromagnetic FeSb$_{3}$
we obtain real-valued phonon frequencies and also a $c_{44}$ greater than zero,
indicating that the system is mechanically as well as dynamically stable.
