Enhanced thermoelectric response of hole-doped La ₂NiO _4+δ from ab initio calculations

Thermoelectric properties of the system La ₂NiO _4+δ have been studied ab initio. Large Seebeck coefficient values are predicted for the parent compound, and to some extent remain in the hole-doped metallic phase, accompanied by an increase in the conductivity. This system, due to its layered structure, would be a suitable candidate for an improvement of its thermoelectric figure of merit by nanostructurization in thin films, which has already been shown to increase the electrical conductivity (σ). Our calculations show that in the region around La ₂NiO _4.05, the system has a large thermopower at high temperatures and also a substantially increased σ. Films grown with this low-doping concentration will show an optimal relationship between thermopower and σ. This result is obtained for various exchange-correlation schemes (correlated, uncorrelated, and parameter free) that we use to analyze the electronic structure of the hole-doped compound.