Electronic structure, bonding character, and thermoelectric properties of semiconducting rhenium silicide with doping

The electronic structure and thermoelectric properties of ReSi_1.75 and its doped systems are studied by the first-principles calculation using the full-potential linearized augmented plane-wave method in the local density approximation with self-interaction correction and the semiclassical Boltzmann theory. ReSi_1.75 shows narrow gap semiconductor behavior with an indirect gap of 0.12 eV and a direct gap of 0.36 eV. The Fermi levels of Al- and Mo-doped systems move into the valence band. The Al-doped compound remains a semiconductor while the gap of Mo-doped compounds becomes small and nearly disappears. The relations between the electronic structure and thermoelectric properties of doped ReSi_1.75 are analyzed and explained in detail. Our calculations strongly suggest that an excellent thermoelectric performance can be obtained for p-doped ReSi_1.75 along [100] and for n-doped ReSi_1.75 along [001] compared with the undoped compound.