First-principles studies of the structural and electronic properties of pyriteFeS2

We present a study of the structural and electronic properties of Pyrite ${\mathrm{FeS}}_{2}$ performed using both localized basis set and plane wave first-principles calculations. Calculations performed using either Gaussian or plane wave basis sets yield results consistent with each other. Small differences in the computed geometries are shown to be due to the choice of pseudopotential employed in the plane wave calculations. The computed densities of states are relatively insensitive to the form of basis set and pseudopotential used. We find that density functional and hybrid approaches predict properties such as geometry and densities of states in good agreement with experiment but that the agreement between the results from Hartree--Fock (HF) calculations and experiment is poor. The reasons for the poor performance of HF theory in this system are examined and are found to be due to the neglect of electronic correlation.