• journal_title：American Mineralogist
• Contributor：Fen Xu ; Alexandra Navrotsky
• Publisher：Mineralogical Society of America
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2010.3334
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：95
• issue：5-6
• firstpage：717
• section：Articles

Binary iron sulfides are of major interest and importance in environmental, geological, and planetary science. Oxidative high-temperature oxide melt drop-solution calorimetry in molten sodium molybdate (3Na₂O·4MoO₃) solvent at 975 K was applied to determine the energetics of formation of the binary iron monosulfide solid solution (pyrrhotite) (Fe_1–0.125xS, 0 ≤ x ≤ 1). The enthalpies of formation from elements are consistent with earlier data in the literature, available for a few compositions. Within the experimental errors, the enthalpies of formation of the solid solution from the end-members Fe_0.875S and FeS (ΔH_mix, kJ/mol) at 25 °C equal to zero. Under the assumption of random distribution of Fe vacancies, the Gibbs free energies of mixing of Fe_1–0.125xS (0 ≤ x ≤ 1) are estimated. Our data support the two-sublattice model proposed by Waldner and Pelton (2005).