Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Fe7S8”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Fe7S8 by Materials Project

Fe7S8 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are four inequivalent Fe+2.29+ sites. In the first Fe+2.29+ site, Fe+2.29+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Fe–S bond distances ranging from 2.10–2.29 Å. In the second Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–59°. There are a spread of Fe–S bond distances ranging from 2.18–2.38 Å. In the third Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–59°. There are a spread of Fe–S bond distances ranging from 2.19–2.46 Å. In the fourth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are a spread of Fe–S bond distances ranging from 2.16–2.39 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe7S8 by Materials Project

Fe7S8 crystallizes in the trigonal P3_121 space group. The structure is three-dimensional. there are five inequivalent Fe+2.29+ sites. In the first Fe+2.29+ site, Fe+2.29+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Fe–S bond distances ranging from 2.10–2.31 Å. In the second Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 50–51°. There are a spread of Fe–S bond distances ranging from 2.18–2.37 Å. In the third Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–60°. There are a spread of Fe–S bond distances ranging from 2.19–2.40 Å. In the fourth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 50–60°. There are a spread of Fe–S bond distances ranging from 2.20–2.41 Å. In the fifth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–60°. There are a spread of Fe–S bond distances ranging from 2.24–2.49 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe7S8 by Materials Project

Fe7S8 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are fourteen inequivalent Fe+2.29+ sites. In the first Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 46–55°. There are a spread of Fe–S bond distances ranging from 2.18–2.51 Å. In the second Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.19–2.44 Å. In the third Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.16–2.55 Å. In the fourth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.17–2.55 Å. In the fifth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.19–2.44 Å. In the sixth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.18–2.51 Å. In the seventh Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.18–2.55 Å. In the eighth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 49–54°. There are a spread of Fe–S bond distances ranging from 2.24–2.32 Å. In the ninth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.18–2.50 Å. In the tenth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.19–2.44 Å. In the eleventh Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.18–2.50 Å. In the twelfth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.19–2.44 Å. In the thirteenth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are a spread of Fe–S bond distances ranging from 2.24–2.32 Å. In the fourteenth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–55°. There are a spread of Fe–S bond distances ranging from 2.17–2.56 Å. There are sixteen inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the third S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fifth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the seventh S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the eighth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the ninth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the tenth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the eleventh S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the twelfth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the thirteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fourteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fifteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the sixteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe7S8 by Materials Project

Fe7S8 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are fourteen inequivalent Fe+2.29+ sites. In the first Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 42–57°. There are a spread of Fe–S bond distances ranging from 2.17–2.72 Å. In the second Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–57°. There are a spread of Fe–S bond distances ranging from 2.17–2.51 Å. In the third Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 42–57°. There are a spread of Fe–S bond distances ranging from 2.18–2.66 Å. In the fourth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Fe–S bond distances ranging from 2.20–2.61 Å. In the fifth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–57°. There are a spread of Fe–S bond distances ranging from 2.16–2.53 Å. In the sixth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 43–56°. There are a spread of Fe–S bond distances ranging from 2.18–2.66 Å. In the seventh Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Fe–S bond distances ranging from 2.19–2.62 Å. In the eighth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 48–55°. There are a spread of Fe–S bond distances ranging from 2.22–2.33 Å. In the ninth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–56°. There are a spread of Fe–S bond distances ranging from 2.18–2.67 Å. In the tenth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Fe–S bond distances ranging from 2.17–2.54 Å. In the eleventh Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 44–55°. There are a spread of Fe–S bond distances ranging from 2.19–2.62 Å. In the twelfth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Fe–S bond distances ranging from 2.18–2.55 Å. In the thirteenth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Fe–S bond distances ranging from 2.22–2.32 Å. In the fourteenth Fe+2.29+ site, Fe+2.29+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 43–57°. There are a spread of Fe–S bond distances ranging from 2.19–2.61 Å. There are sixteen inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the second S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the fifth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the seventh S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the eighth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the ninth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe+2.29+ atoms. In the tenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the eleventh S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the twelfth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the thirteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fourteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the fifteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms. In the sixteenth S2- site, S2- is bonded in a 5-coordinate geometry to five Fe+2.29+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1995

The rate of pyrite decomposition on the surface of Venus

We report the results of a detailed experiment study of the kinetics and mechanism of pyrite (FeS2) chemical weathering under Venus surface conditions. Pyrite is thermodynamically unstable on the surface of Venus and will spontaneously decompose to pyrrhotite (Fe7S8) because the observed S2 partial pressure in the lower atmosphere of Venus is lower than the S2 vapor pressure over coexisting pyrite and pyrrhotite. Pyrite decomposition kinetics were studied in pure CO2 and CO2 gas mixtures along five isotherms in the temperature range 390-531 C. In all gas mixtures studied, pyrite thermally decomposes to pyrrhotite (Fe7S8), which on continued heating loses sulfur to form more Fe-rich pyrrhotites. During this process the pyrrhotites are also being oxidized to form magnetite (Fe3O4), which converts to maghemite (gamma-Fe2O3), and then to hematite (alpha-Fe2O3). The reaction rates for pyrite thermal decomposition to pyrrhotite were determined by measuring the weight loss. The thickness of the unreacted pyrite in the samples provided a second independent reaction rate measurement. Finally, Mossbauer spectra done on 42 of the 115 experimental samples provided a third set of independent reaction rate data. Pyrite decomposition follows zero-order kinetics and is independent of the amount of pyrite present. The rate of pyrite decomposition is apparently independent of the gas compositions used and of the CO2 number density over a range of a factor of 40. The derived activation energy of approximately 150 kJ/mole is the same in pure CO2, two different CO-CO2 mixtures, and a ternary CO-SO2-CO2 mixture. Based on data for a CO-CO2-SO2 gas mixture with a CO number density approximately 10 times higher than at the surface of Venus and a SO2 number density approximately equal to that at the surface of Venus, the rate of pyrite destruction on the surface of Venus varies from about 1225 +/- 238 days/cm at the top of Maxwell Montes (approximately 660 K) to about 233 +/- 133 days/cm in the plains of Venus (approximately 740 K). These lifetimes are very short on a geological time scale and show that pyrite cannot exist on the surface of Venus for any appreciable length of time.

Fegley, B., Jr.↗