Full potential band structure calculation of iron pyrite

The semiconductor iron pyrite has recently attracted much interest again due to its promising capabilities for photovoltaic applications as well as a possible material for solid-state batteries. It also shows an unusual blue shift of the optical gap under pressure. We present a full potential total energy calculation of iron pyrite using density functional theory with a non-orthogonal local orbital minimum basis scheme (K. Koepernik, H. Eschrig, Phys. Rev. B 59 (1999) 1743). We obtain a good agreement between our calculations and experimental values for the lattice constant, the positions of the sulfur atoms in the lattice and the bulk modulus. A study of the effect of isotropic external pressure on the electronic structure of pyrite gives new insight into the optical properties of pyrite.