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NASA NTRS2004

Lunar and Planetary Science XXXV: Chondrules: The Never-Ending Story

The session "Chondrules: The Never-Ending Story" included the following reports:Dust Size Distribution in Solar Nebula Inferred from Shock-Wave Heating Model for Chondrule Formation; Collisional Destruction of Chondrules in Shock Waves and Inferred Dust to Gas Mass Ratio; Evaporation and Accompanying Isotopic Fractionation of Sulfur from Fe-S Melt During Shock Wave Heating ; Evaporation During Chondrule Formation, Recondensation as Fine Particles, and the Condensation of S and Other Volatile Elements; Fe Isotopes and the Formation of Chondrules; Pristine and Processed Metal in CR Chondrites: Condensation in the Solar Nebula and Partial Reequilibration During Chondrule Formation; Variation of the Condensation Path of Supercooled Silicate Melt; Volatile and Moderately Volatile Trace Element Composition of Chondrules and Matrix from CM Chondrites: Implications for Chondrule Formation; Opaque Mineral Assemblages at Chondrule Boundaries in the Vigarano CV Chondrite: Evidence for Gas-Solid Reactions Following Chondrule Formation; Forsterite and Olivine in Sahara-97210 (LL3.2) and Chainpur (LL3.4) Chondrules: Compositional Evolution and the Influence of Melting; The Vaguries of Pyroxene Nucleation and the Resulting Chondrule Textures; Contemporaneous Formation of Chondrules in the Al-26-Mg-26 System for Ordinary and CO Chondrites; and Al-Mg Isotopic Systematics in Ferromagnesian Chondrules from the Unequilibrated Ordinary Chondrite.

Source record↗

NASA NTRS2004

Metal-Silicate Segregation in Deforming Dunitic Rocks: Applications to Core Formation in Europa and Ganymede

Core formation is an important event in the evolution of a planetary body, affecting both the geochemical and geophysical properties of the body. Metal-silicate segregation could have proceeded either by settling of liquid metal through a magma ocean or by percolation of liquid metal through a solid silicate mantle. Percolation of metallic melt had previously been excluded as a viable segregation mechanism because metallic melts do not form an interconnected network under hydrostatic conditions, except at high melt fraction (>5 vol%), due to the high dihedral angle between metals and silicates (>60 ). Without an interconnected network, porous flow of metallic melt is impossible, leaving the magma ocean scenario as the only mechanism to form the core. Moment-of-inertia measurements of Europa and Ganymede from the Galileo probe indicate that they are differentiated. This evidence suggests that a method for segregating metals and silicates at temperatures low enough to retain volatile compounds must exist. We have investigated the effect of deformation on the distribution of metallic melts in silicates. We have deformed samples of olivine + 5-9 vol% Fe-S to strains of 2.5 in simple shear and find that the metallic melt segregates into melt-rich planes oriented at 20 to the shear plane. These metallic melt-rich bands are similar in structure to the silicate melt-rich bands reported by Holtzman, indicating that deformation can interconnect isolated metallic melt pockets and allow porous flow of non-wetting melts. Such a core formation process could have occurred in the jovian satellites.

Hustoft, J. W.↗

NASA NTRS2007

Processes in Early Planetesimals: Evidence from Ureilite Meteorites

Ureilites are primitive ultramafic achondrites composed largely of olivine and pigeonite, with minor augite, carbon, sulphide and metal. They represent very early material in the history of the Solar System and form a bridge between undifferentiated chondrites and fully differentiated asteroids. They show a mixture of chemical characteristics, some of which are considered to be nebula-derived (e.g. a negative correlation between Mg/Fe and Delta O-17 that resembles that of the ordinary chondrites but at lower Delta O-17 values) whereas others have been imposed by asteroidal differentiation. Carbon isotope data show a striking negative correlation of delta C-13 values with mg# in olivine. delta C-13 also correlates positively with Delta O-17, and therefore this isotopic variation was probably also nebula-derived. Thus, oxygen and carbon isotope compositions and Fe-Mg systematics of each monomict ureilite were established before differentiation processes began. Heated by decay of short-lived radioactive isotopes, the ureilite asteroid started to melt. Metal and sulphide would have melted first, forming a Fe-S eutectic liquid, which removed chalcophile elements and incompatible siderophile elements, and basaltic melts that removed Al, Ca and the LREE. Several elements show different abundances and/or correlations with Fo content in olivine, e.g. carbon shows a positive correlation in ferroan ureilites, and a weak or even negative correlation in more magnesian compositions. HSE such as Os and Ir also show different distributions, i.e. ureilites with Fo < 82 have very scattered Os and Ir concentrations, which reach high values, whereas ureilites with Fo > 82 tend to have much less scattered and overall lower Os and Ir abundances. A similar change in elemental behaviour is shown by the Fe-Mn relations in ureilitic olivines: those with Fo contents < 85 show a good negative correlation, whereas those with Fo > 85 show much greater scatter. This suggests that a major change affected the parent body at a time when melting had reached relatively magnesian bulk compositions. We consider that this event may have been a hit and run collision in which the ureilite parent body collided with a larger object. During the collision, the ureilite mantle broke up catastrophically but re-accreted in a jumbled state around the still-intact core. Mg-rich basaltic melts that were in the process of being formed at the time of break-up were retained in part as melt clasts that re-accreted to the regolith and are found in polymict ureilites.

Mittlefehldt, David W.↗

NASA NTRS2010

Oxidation States of Grim Glasses in EET79001 Based on Vanadium Valence

Gas-rich impact-melt (GRIM) glasses in SNC meteorites are very rich in Martian atmospheric noble gases and sulfur suggesting a possible occurrence of regolith-derived secondary mineral assemblages in these samples. Previously, we have studied two GRIM glasses, 506 and 507, from EET79001 Lith A and Lith B, respectively, for elemental abundances and spatial distribution of sulfur using EMPA (WDS) and FE-SEM (EDS) techniques and for sulfur-speciation using K-edge XANES techniques. These elemental and FE-SEM micro-graph data at several locations in the GRIM glasses from Shergotty (DBS), Zagami 994 and EET79001, Lith B showed that FeO and SO3 are positively correlated (SO3 represents a mixture of sulfide and sulfate). FE-SEM (EDS) study revealed that the sulfur-rich pockets in these glasses contain numerous micron-sized iron-sulfide (Fe-S) globules sequestered throughout the volume. However, in some areas (though less frequently), we detected significant Fe-S-O signals suggesting the occurrence of iron sulfate. These GRIM glasses were studied by K-edge microXANES techniques for sulfur speciation in association with iron in sulfur-rich areas. In both samples, we found the sulfur speciation dominated by sulfide with minor oxidized sulfur mixed in with various proportions. The abundance of oxidized sulfur was greater in 506 than in 507. Based on these results, we hypothesize that sulfur initially existed as sulfate in the glass precursor materials and, on shock-impact melting of the precursor materials producing these glasses, the oxidized sulfur was reduced to predominately sulfide. In order to further test this hypothesis, we have used microXANES to measure the valence states of vanadium in GRIM glasses from Lith A and Lith B to complement and compare with previous analogous measurements on Lith C (note: 506 and 507 contain the largest amounts of martian atmospheric gases but the gas-contents in Lith C measured by are unknown). Vanadium is ideal for addressing this re-dox issue because it has multiple valence states and is a well-studied element. Ferrous-dominated iron valences determined by microXANES on the Lith A and Lith B glasses provide little redox sensitivity. Vanadium valence measurements for impact glass in Lith C at three different locations yielded valence values of 3.1, 3.2 and 3.4 with inferred fO2 values of IW-0.7, IW-0.1 and IW+0.7, respectively. This range of oxygen-fugacity values is understandable because the glasses are shock-molten impact glasses which are heterogeneous in nature. Oxygen fugacity values obtained from the analysis of Fe-Ti oxides and Eu partitioning in pyroxenes from EET79001 Lith A and Lith B (host lithologies) were in the range of IW+0.3 to IW+1.9 suggesting that V in the Lith C impact glass was reduced in the impact process. Here, we examine whether the 506 from Lith A and 507 from Lith B GRIM glasses yield similar or different fO2 values from those of Lith C using the vanadium K-edge microXANES technique.

Sutton, S. R.↗

NASA NTRS2011

Acid-Sulfate-Weathering Activity in Shergottite Sites on Mars Recorded in Grim Glasses

Based on mass spectrometric studies of sulfur species in Shergotty and EET79001, [1] and [2] showed that sulfates and sulfides occur in different proportions in shergottites. Sulfur speciation studies in gas-rich impact-melt (GRIM) glasses in EET79001 by the XANES method [3] showed that S K-XANES spectra in GRIM glasses from Lith A indicate that S is associated with Ca and Al presumably as sulfides/sulfates whereas the XANES spectra of amorphous sulfide globules in GRIM glasses from Lith B indicate that S is associated with Fe as FeS. In these amorphous iron sulfide globules, [4] found no Ni using FE-SEM and suggested that the globules resulting from immiscible sulfide melt may not be related to the igneous iron sulfides having approximately 1-3% Ni. Furthermore, in the amorphous iron sulfides from 507 GRIM glass, [5] determined delta(sup 34)S values ranging from +3.5%o to -3.1%o using Nano-SIMS. These values plot between the delta(sup 34)S value of +5.25%o determined in the sulfate fraction in Shergotty [6] at one extreme and the value of -1.7%o obtained for igneous sulfides in EET79001 and Shergotty [7] at the other. These results suggest that the amorphous Fe-S globules likely originated by shock reduction of secondary iron sulfate phases occurring in the regolith precursor materials during impact [7]. Sulfates in the regolith materials near the basaltic shergottite sites on Mars owe their origin to surficial acid-sulfate interactions. We examine the nature of these reactions by studying the composition of the end products in altered regolith materials. For the parent material composition, we use that of the host shergottite material in which the impact glasses are situated.

Rao, M. N.↗

NASA NTRS2012

Gravity, Topography, and Magnetic Field of Mercury from Messenger

On 18 March 2011, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was inserted into a 12-hour, near-polar orbit around Mercury, with an initial periapsis altitude of 200 km, initial periapse latitude of 60 deg N, and apoapsis at approximately 15,200 km altitude in the southern hemisphere. This orbit has permitted the mapping of regional gravitational structure in the northern hemisphere, and laser altimetry from the MESSENGER spacecraft has yielded a geodetically controlled elevation model for the same hemisphere. The shape of a planet combined with gravity provides fundamental information regarding its internal structure and geologic and thermal evolution. Elevations in the northern hemisphere exhibit a unimodal distribution with a dynamic range of 9.63 km, less than that of the Moon (19.9 km), but consistent with Mercury's higher surface gravitational acceleration. After one Earth-year in orbit, refined models of gravity and topography have revealed several large positive gravity anomalies that coincide with major impact basins. These candidate mascons have anomalies that exceed 100 mGal and indicate substantial crustal thinning and superisostatic uplift of underlying mantle. An additional uncompensated 1000-km-diameter gravity and topographic high at 68 deg N, 33 deg E lies within Mercury's northern volcanic plains. Mercury's northern hemisphere crust is generally thicker at low latitudes than in the polar region. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR2 = 0.353 +/- 0.017, where M=3.30 x 10(exp 23) kg and R=2440 km are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of Cm/C = 0.452 +/- 0.035. One proposed model for Mercury's radial density distribution consistent with these results includes silicate crust and mantle layers overlying a dense solid (possibly Fe-S) layer, a liquid Fe-rich outer core of radius 2030 +/- 37 km, and an assumed solid inner core. Magnetic field measurements indicate a northward offset of Mercury's axial magnetic dipole from the geographic equator by 479 +/-3 km and provide evidence for a regional-scale magnetic field approximately collocated with the northern volcanic plains of possible crustal origin. These results from MESSENGER indicate a complex and asymmetric evolution of internal structure and dynamics in this end-member inner planet.

Neumann, Gregory A.↗

NASA NTRS2015

Experiments on Lunar Core Composition: Phase Equilibrium Analysis of A Multi-Element (Fe-Ni-S-C) System

Previous geochemical and geophysical experiments have proposed the presence of a small, metallic lunar core, but its composition is still being investigated. Knowledge of core composition can have a significant effect on understanding the thermal history of the Moon, the conditions surrounding the liquid-solid or liquid-liquid field, and siderophile element partitioning between mantle and core. However, experiments on complex bulk core compositions are very limited. One limitation comes from numerous studies that have only considered two or three element systems such as Fe-S or Fe-C, which do not supply a comprehensive understanding for complex systems such as Fe-Ni-S-Si-C. Recent geophysical data suggests the presence of up to 6% lighter elements. Reassessments of Apollo seismological analyses and samples have also shown the need to acquire more data for a broader range of pressures, temperatures, and compositions. This study considers a complex multi-element system (Fe-Ni-S-C) for a relevant pressure and temperature range to the Moon's core conditions.

Go, B. M.↗

NASA NTRS2022

X-Ray Amorphous Sulfur-Bearing Phases in Sedimentary Rocks of Gale Crater, Mars

The Curiosity rover in Gale crater is investigating a mineral transition observed from orbit—an older “clay unit” to a younger “sulfate unit”—hypothesized to reflect the aridification of Mars' climate. Below this transition, the rover detected crystalline Ca-sulfates with minor Fe-sulfates but also found that some fraction of a rock's bulk SO 3 is often in the poorly constrained X-ray amorphous component. Here, we characterize the abundances and compositions of the X-ray amorphous sulfur-bearing phases in 19 drilled samples using a mass balance approach, and in a subset of 5 samples using evolved SO 2 gas measured using the SAM instrument. We find that ∼20–90 wt% of a sample's bulk SO 3 is in the X-ray amorphous state and that X-ray amorphous sulfur-bearing phase compositions are consistent with mixtures of Mg-S, Fe-S, and possibly Ca-S phases, likely sulfates or sulfites. These phases reside in the bedrock, perhaps as cementing agents deposited with detrital sediments or during early diagenesis, and in diagenetic alteration halos deposited after lithification during late diagenesis. The likely presence of highly soluble Mg-sulfates in the rocks suggests negligible fluid flow through the bedrock post-Mg-sulfate deposition. The X-ray amorphous sulfur-bearing phases probably became amorphous through dehydration in the current Martian atmosphere or inside the CheMin instrument. X-ray amorphous sulfur-bearing materials likely contribute to orbital spectral detections of sulfates, and so our results help form multiple hypotheses to be tested in the sulfate unit and are important for understanding the evolution of the Martian surface environment at Gale crater.

R. J. Smith↗

DOE OSTI2020

Leveraging computational genomics to understand the molecular basis of metal homeostasis

Genome-based data is helping to reveal the diverse strategies plants and algae use to maintain metal homeostasis. In addition to acquisition, distribution and storage of metals, acclimating to feast or famine can involve a wealth of genes that we are just now starting to understand. The fast-paced acquisition of genome-based data, however, is far outpacing our ability to experimentally characterize protein function. Computational genomic approaches are needed to fill the gap between what is known and unknown. To avoid misconstruing bioinformatically derived data, which is the root cause of the inaccurate functional annotations that plague databases, functional inferences from diverse sources and contextualization of that evidence with a robust understanding of protein family evolution is needed. Phylogenomic- and comparative-genomic-based studies can aid in the interpretation of experimental data or provide a spark for the discovery of a new function. These analyses not only lead to novel insight into a target protein's function but can generate thought-provoking insights across protein families.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Materials Data on FeS2 by Materials Project

FeS2 is Marcasite structured and crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent S+1.50- atoms to form a mixture of edge and corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are two shorter (2.23 Å) and four longer (2.24 Å) Fe–S bond lengths. S+1.50- is bonded in a 4-coordinate geometry to three equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Fe3S4 by Materials Project

Fe3S4 is Calaverite-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three Fe3S4 sheets oriented in the (0, 0, 1) direction. there are three inequivalent Fe+2.67+ sites. In the first Fe+2.67+ site, Fe+2.67+ is bonded to six S2- atoms to form distorted edge-sharing FeS6 pentagonal pyramids. All Fe–S bond lengths are 2.37 Å. In the second Fe+2.67+ site, Fe+2.67+ is bonded in a 6-coordinate geometry to six S2- atoms. There are three shorter (2.18 Å) and three longer (2.57 Å) Fe–S bond lengths. In the third Fe+2.67+ site, Fe+2.67+ is bonded in a 6-coordinate geometry to six S2- atoms. There are three shorter (2.16 Å) and three longer (2.58 Å) Fe–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Fe+2.67+ atoms. In the second S2- site, S2- is bonded to six Fe+2.67+ atoms to form a mixture of distorted edge, corner, and face-sharing SFe6 octahedra. The corner-sharing octahedral tilt angles are 44°. In the third S2- site, S2- is bonded to six Fe+2.67+ atoms to form a mixture of distorted edge, corner, and face-sharing SFe6 octahedra. The corner-sharing octahedral tilt angles are 44°. In the fourth S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Fe+2.67+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on FeS by Materials Project

FeS is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe2+ is bonded to six equivalent S2- atoms to form a mixture of face, edge, and corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 48°. All Fe–S bond lengths are 2.43 Å. S2- is bonded to six equivalent Fe2+ atoms to form a mixture of distorted edge and corner-sharing SFe6 pentagonal pyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on FeS by Materials Project

FeS is Modderite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Fe2+ is bonded to six equivalent S2- atoms to form a mixture of edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 45–58°. There are a spread of Fe–S bond distances ranging from 2.22–2.37 Å. S2- is bonded in a 6-coordinate geometry to six equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Fe3S4 by Materials Project

Fe3S4 is Hausmannite structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Fe+2.67+ sites. In the first Fe+2.67+ site, Fe+2.67+ is bonded to four equivalent S2- atoms to form corner-sharing FeS4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. All Fe–S bond lengths are 2.14 Å. In the second Fe+2.67+ site, Fe+2.67+ is bonded to six equivalent S2- atoms to form FeS6 octahedra that share corners with six equivalent FeS4 tetrahedra and edges with six equivalent FeS6 octahedra. All Fe–S bond lengths are 2.34 Å. S2- is bonded in a distorted rectangular see-saw-like geometry to four Fe+2.67+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on FeS by Materials Project

FeS crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six S2- atoms to form distorted FeS6 octahedra that share corners with four equivalent FeS6 octahedra, corners with five equivalent FeS5 trigonal bipyramids, edges with two equivalent FeS6 octahedra, and edges with two equivalent FeS5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 56–57°. There are a spread of Fe–S bond distances ranging from 2.23–2.58 Å. In the second Fe2+ site, Fe2+ is bonded to five S2- atoms to form distorted FeS5 trigonal bipyramids that share corners with five equivalent FeS6 octahedra, corners with four equivalent FeS5 trigonal bipyramids, and edges with two equivalent FeS6 octahedra. The corner-sharing octahedra tilt angles range from 47–68°. There are a spread of Fe–S bond distances ranging from 2.14–2.25 Å. In the third Fe2+ site, Fe2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Fe–S bond distances ranging from 2.16–2.50 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Fe2+ atoms. In the second S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the third S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on FeS by Materials Project

FeS is Modderite-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twelve inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the second Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the third Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–66°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the fourth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the fifth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the sixth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the seventh Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the eighth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the ninth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.29–2.81 Å. In the tenth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the eleventh Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–65°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. In the twelfth Fe2+ site, Fe2+ is bonded to six S2- atoms to form a mixture of distorted edge, corner, and face-sharing FeS6 octahedra. The corner-sharing octahedra tilt angles range from 33–66°. There are a spread of Fe–S bond distances ranging from 2.28–2.81 Å. There are twelve inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the second S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the third S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the fifth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the sixth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the seventh S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the eighth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the ninth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the tenth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the eleventh S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms. In the twelfth S2- site, S2- is bonded in a 6-coordinate geometry to six Fe2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on FeS by Materials Project

FeS is lead oxide structured and crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one FeS sheet oriented in the (0, 0, 1) direction. Fe2+ is bonded to four equivalent S2- atoms to form a mixture of edge and corner-sharing FeS4 tetrahedra. All Fe–S bond lengths are 2.17 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗

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↗