Marcasite revisited: Optical absorption gap at room temperature

Jagadeesh and Seehra published in 1980 that the marcasite band gap energy is 0.34 eV. However, recent calculations and experimental approximations accomplished by several research groups point out that the marcasite band gap energy should be quite similar to that of pyrite (of the order of 0.8-1.0 eV). By using diffuse reflectance spectroscopy (DRS) we have determined that marcasite has no optical absorption gap at photon energies 0.06≤hν≤0.75eV and that it has two well defined optical transitions at ~0.9eV and ~2.2eV quite similar to those of pyrite. Marcasite optical absorption gap appears to be Eg≅0.83±0.02eV and it is due to an allowed indirect transition.