  Electronic structure and thermoelectric properties of marcasite (m) and
synthetic pyrite (p) phases of FeX$_2$ (X=Se,Te) have been investigated using
first principles density functional theory and Boltzmann transport equation.
The plane wave pseudopotential approximation was used to study the structural
properties and full-potential linear augmented plane wave method was used to
obtain the electronic structure and thermoelectric properties (thermopower and
power factor scaled by relaxation time). From total energy calculations we find
that m-FeSe$_2$ and m-FeTe$_2$ are stable at ambient conditions and no
structural transition from marcasite to pyrite is seen under the application of
hydrostatic pressure. The calculated ground state structural properties agree
quite well with available experiments. From the calculated thermoelectric
properties, we find that both m and p forms are good candidates for
thermoelectric applications. However, hole doped m-FeSe$_2$ appears to be the
best among all the four systems.

Materials Science