Surface Energetics of Iron Pyrite

Event Center A & B

We studied the surface energetics of iron pyrite to determine the most stable surface configuration. Interest in this research stems from current application of iron pyrite as a photovoltaic. We would like to understand if surface stoichiometry is responsible for the low Open Circuit Voltage. Density Functional Theory calculations using VASP (Ab-initio Simulation Package) were performed and PAW potentials and the GGA+Hubbard U correction was used. The plane wave energy cutoff as 310eV, and for each cycle the total energy was converged within 1E-06 eV. A Monkhorst pack k-mesh of 9x9x9 was used for bulk relaxations, and a 4x4x1 k-mesh for the surface. DOS and band structure were ran first by a self consistent calculation, and then a non-self consistent run using CHGCAR with a k-mesh of 12x12x1. Bulk (single crystal) of iron pyrite is known to be an n-type semiconductor, and the Fermi level lies closer to the conduction band. While the surface (thin film) is commonly a p-type semi conductor and the Fermi level lies closer to the valance band.