Structural evolution from iron sulfide nanoparticle to pyrite

Abstract

FeS nanoparticle, known as a precursor of pyrite, is formed in anaerobic marine sediments. In this study, we investigated structural changes from the FeS nanoparticle to pyrite by using hydrothermal experiment, synchrotron XRD measurement, and XAFS measurement. The XRD pattern of synthesized FeS nanoparticle corresponds to that of nanocrystalline mackinawite. The mackinawite transforms to pyrite by the addition of sulfur, but it partially transforms to greigite. While the coordination of Fe changes from FeS₄ tetrahedron to FeS₆ octahedron, the valence of Fe remains divalent.