Periodic DFT+U investigation of the bulk and surface properties of marcasite (FeS2)

Marcasite FeS2 and its surface properties have been investigated by Hubbard-corrected Density Functional Theory (DFT+U) calculations. The calculated structural parameters, interatomic bond distances, elastic constants and electronic properties of the bulk mineral were determined and compared with earlier theoretical reports and experimental data where available. We have also investigated the relative stabilities, interlayer spacing relaxations, work functions, and electronic structures of the {010}, {101}, {110} and {130} surfaces under dehydrated and hydrated conditions. Using the calculated surface energies, we have derived the equilibrium crystal shape of marcasite from a Wulff construction. The {101} and {010} surfaces dominate the marcasite crystallite surface area under both dehydrated and hydrated conditions, in agreement with their relative stabilities compared to the other surfaces. The simulated scanning tunneling microscopy (STM) images of the {101} and {010} facets are also presented, for comparison with future experiments.