SEARCH · Engineering Papers
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.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
(Fe(SO4)2)2N2 crystallizes in the trigonal P321 space group. The structure is two-dimensional and consists of one ammonia molecule and one Fe(SO4)2 sheet oriented in the (0, 0, 1) direction. In the Fe(SO4)2 sheet, Fe3+ is bonded to six equivalent O2- atoms to form distorted FeO6 octahedra that share corners with six equivalent SO4 tetrahedra. All Fe–O bond lengths are 2.02 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 35°. There is one shorter (1.45 Å) and three longer (1.50 Å) S–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S6+ atom.
The age distribution of 261 field localities, sampled for their well-preserved Archean and Proterozoic sedimentary rocks, revealed a 500-700 Ma episodicity. Assuming that the numbers of sites are a proxy for mass of sediments, the record of well-preserved sediments is more abundant in the intervals 3.5-3.3, 2.8-2.5, 2.1-1.8, 1.5-1.3, and 1.0-0.54 Ga than in the intervening intervals. It is proposed that the crustal inventory of photosynthetic organic carbon was modulated by the volume of sedimentation in sites favorable for the burial and long-term preservation of organic carbon. Tectonic processes controlled this sediment volume. Episodic increases in the organic inventory led to stepwise increases in oxidized reservoirs (e.g., O2, SO4(2-), Fe(3+). The interval 2.9-2.5 Ga recorded a large rise in seawater Sr-87/Sr-86, the oldest-known extensive banded iron formations, and the first evidence (C-13-depleted kerogens) of O2 use by methylotrophic bacteria. The interval 2.2-1.8 Ga has both carbon isotopic evidence for a stepwise increase in the organic reservoir and also paleosol evidence for an O2 increase. The interval 1.1-0.6 Ga shows isotopic evidence for another organic carbon increase. The interval 1.5-1.3 Ga revealed no such increases as yet, perhaps because incomplete rifting of the mid-Proterozoic supercontinent was associated with extensive sedimentation in oxidized continental basins, producing redbeds, coarse clastics, etc. Such sedimentation did not promote the burial of reduced carbon.
Evidence is presented for the possible existence of ferric sulfato complexes and hydroxo ferric sulfate minerals in the permafrost of Mars. A sequential combination of ten unique conditions during the cooling history of Mars is suggested which is believed to have generated an environment within Martian permafrost that has stabilized Fe(3+)-SO4(2-)-bearing species. It is argued that minerals belonging to the jarosite and copiapite groups could be present in Martian regolith analyzed in the Viking XRF measurements at Chryse and Utopia, and that maghemite suspected to be coating the Viking magnet arrays is a hydrolysate of dissolved ferric sulfato complexes from exposed Martian permafrost.
In order to predict what biomarkers could be used on Mars, several biomarkers, or key signatures, of extinct life on earth are identified. Some of these biomarkers which may be applicable to Mars include reduced carbon and nitrogen compounds, CO3(2-), SO4(2-), NO3(-), Mg, Mn, Fe, and the isotopic ratios of C, N, and S. It is suggested that a fully equipped Mars rover might be able to perform analyses to measure most of these biomarkers while on the Martian surface.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
RbFe(SO4)2 crystallizes in the trigonal P321 space group. The structure is three-dimensional. Rb1+ is bonded to twelve O2- atoms to form distorted RbO12 cuboctahedra that share edges with six equivalent RbO12 cuboctahedra, edges with six equivalent SO4 tetrahedra, and faces with two equivalent FeO6 octahedra. There are six shorter (3.03 Å) and six longer (3.40 Å) Rb–O bond lengths. Fe3+ is bonded to six equivalent O2- atoms to form distorted FeO6 octahedra that share corners with six equivalent SO4 tetrahedra and faces with two equivalent RbO12 cuboctahedra. All Fe–O bond lengths are 2.00 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent FeO6 octahedra and edges with three equivalent RbO12 cuboctahedra. The corner-sharing octahedral tilt angles are 35°. There is one shorter (1.47 Å) and three longer (1.49 Å) S–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Rb1+, one Fe3+, and one S6+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent Rb1+ and one S6+ atom.
Li1.0Fe(SO4)2 crystallizes in the monoclinic Pc space group. The structure is three-dimensional. there are four inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 1.90–2.52 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 1.92–2.41 Å. In the third Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 1.95–2.60 Å. In the fourth Li1+ site, Li1+ is bonded to six O2- atoms to form distorted LiO6 pentagonal pyramids that share corners with four FeO6 octahedra, corners with two SO4 tetrahedra, and edges with two SO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–59°. There are a spread of Li–O bond distances ranging from 1.99–2.29 Å. There are four inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one LiO6 pentagonal pyramid and corners with six SO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.98–2.12 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one LiO6 pentagonal pyramid and corners with six SO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.98–2.11 Å. In the third Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 2.03–2.09 Å. In the fourth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent LiO6 pentagonal pyramids and corners with six SO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 2.02–2.08 Å. There are eight inequivalent S6+ sites. In the first S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra and a cornercorner with one LiO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 37–46°. There are a spread of S–O bond distances ranging from 1.47–1.51 Å. In the second S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra and an edgeedge with one LiO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 47–48°. There are a spread of S–O bond distances ranging from 1.44–1.52 Å. In the third S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra. The corner-sharing octahedra tilt angles range from 44–46°. There are a spread of S–O bond distances ranging from 1.45–1.50 Å. In the fourth S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra. The corner-sharing octahedra tilt angles range from 42–49°. There are a spread of S–O bond distances ranging from 1.43–1.53 Å. In the fifth S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra. The corner-sharing octahedra tilt angles range from 39–48°. There are a spread of S–O bond distances ranging from 1.44–1.53 Å. In the sixth S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra and a cornercorner with one LiO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 46–50°. There are a spread of S–O bond distances ranging from 1.45–1.51 Å. In the seventh S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra. The corner-sharing octahedra tilt angles range from 47–48°. There are a spread of S–O bond distances ranging from 1.45–1.52 Å. In the eighth S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three FeO6 octahedra and an edgeedge with one LiO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 38–47°. There are a spread of S–O bond distances ranging from 1.45–1.52 Å. There are thirty-two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Li1+ and one S6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Fe3+, and one S6+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe3+ and one S6+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Li1+ and one S6+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to one Li1+ and one S6+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe3+ and one S6+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Fe3+, and one S6+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the fifteenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Li1+ and one S6+ atom. In the sixteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the eighteenth O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the nineteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the twentieth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the twenty-first O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the twenty-second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Fe3+, and one S6+ atom. In the twenty-third O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the twenty-fourth O2- site, O2- is bonded in a 2-coordinate geometry to two Li1+ and one S6+ atom. In the twenty-fifth O2- site, O2- is bonded in a bent 120 degrees geometry to one Li1+ and one S6+ atom. In the twenty-sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the twenty-seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe3+ and one S6+ atom. In the twenty-eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the twenty-ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Fe3+, and one S6+ atom. In the thirtieth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom. In the thirty-first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Li1+ and one S6+ atom. In the thirty-second O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Fe3+, and one S6+ atom.
Theories for the origin of life require the availability of reduced nitrogen. In the non-reducing atmosphere suggested by geochemical evidence, production in the atmosphere and survival of NH3 against photochemical destruction are problematic. Electric discharges and impact shocks would produce NO rather than HCN or NH3. Conversion of NO to nitrous and nitric acid (by way of HNO) and precipitation in acid rain would provide a source of fixed nitrogen to the early ocean. One solution to the NH3 problem may have been the reduction of nitrite/nitrate in the ocean with aqueous ferrous iron, Fe(2+): 6Fe(+2) + 7 H2O + NO2(-) yields 3Fe2O3 + 11 H(+) + NH3. We have measured the kinetics of this reaction as a function of temperature, pH, and concentrations of salts, Fe(+2), and NO2(-). Cations (Na(+), Mg(2+), K(+)) and anions (Cl(-), Br(-), SO4(2-)) increase the rate by factors of 4 to 8. Although a competing pathway yields N2, the efficiency of the conversion of nitrite to ammonia ranges from 25% to 85%. Nitrate reduction was not consistently reproducible; however, when it was observed, its rate was slower by at least 8X than that of nitrite reduction. If the prebiotic atmosphere contained 0.2 to 10 atmospheres CO2 as suggested by Walker (1985), the Fe(+2) concentration and the rate would have been limited by siderite (FeCO3) solubility.
NaFe(SO4)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are two shorter (2.45 Å) and four longer (2.66 Å) Na–O bond lengths. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six equivalent SO4 tetrahedra. There are two shorter (1.99 Å) and four longer (2.04 Å) Fe–O bond lengths. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–45°. There are a spread of S–O bond distances ranging from 1.45–1.51 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and one S6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one S6+ atom.
A model of acid weathering is proposed for the iron-rich basalts on Mars. Aqueous oxidation of iron sulfides released SO4(2-) and H(+) ions that initiated the dissolution of basaltic ferromagnesian silicates and released Fe(2+) ions. The Fe(2+) ions eventually underwent ferrolysis reactions and produced insoluble hydrous ferric oxide phases. Measurements of the time-dependence of acid weathering reactions show that pyrrhotite is rapidly converted to pyrite plus dissolved ferrous iron, the rate of pyrite formation decreasing with rising pH and lower temperatures. On Mars, oxidation rates of dissolved Fe(2+) ions in equatorial melt-waters in contact with the atmosphere are estimated to lie in the range 0.3-3.0 ppb Fe/yr over the pH range 2 to 6. Oxidation of Fe(2+) ions is estimated to be extremely slow in brine eutectic solutions that might be present on Mars and to be negligible in the frozen regolith.
Large-scale stationary storage forms a key sector that can be economically served by sodium-ion batteries. In realizing practical sodium-ion batteries, discovery and development of novel cathodes is essential. In this spirit, alluaudite-type Na 2 Fe 2 (SO 4 ) 3 was reported in 2014 to have the highest Fe 3+ /Fe 2+ redox potential (~3.8 V vs. Na). This finding led to reports on various PO4 3– and SO4 2– based alluaudite compounds exhibiting high energy densities. In 2017, MoO 4 2– based alluaudite, Na 2.67 Mn 1.67 (MoO 4 ) 3 , was found as a 3.45 V cathode material. Exploring molybdenum chemistry further, this work reports alluaudite type Na 3.36 Co 1.32 (MoO 4 ) 3 (NCMo) as a novel versatile electroactive cathode for Li-ion and Na-ion batteries. It was synthesized by a wet solution-combustion route with a restricted annealing duration of 1 min at 600 °C. Calorimetric study revealed the formation enthalpy from component oxides (ΔH° f,ox = –575.49 ± 7.75 kJ/mol) to be highly exothermic. Unlike the sulfate class of alluaudites, this material is highly stable in air and moisture (ΔH ds = 537.42 ± 0.78 kJ/mol). Having an ionic conductivity of 6.065 × 10 –8 S/cm (at 50 °C), it offers a pseudo two-dimensional Na + migration pathway. Without any material optimization, NCMo was found to work as a high-voltage insertion cathode (ca. 4.0 V vs. Na/Na + and 4.1 V vs. Li/Li + ) in sync with theoretically predicted potential of 3.98 V (vs. Na/Na + ). Ex-situ X-ray diffraction and photoelectron spectroscopy studies revealed the occurrence of solid-solution redox mechanism solely involving Co 3+ /Co 2+ redox centre. Finally, it benchmarks Na 3.36 Co 1.32 (MoO 4 ) 3 as a novel electrochemically active Mo-based alluaudite-type polyanionic cathode insertion material.
Green rusts (GR) are mixed-valence iron (Fe) hydroxides which form in reducing redox environments like riparian and wetland soils and shallow groundwater. In these environments, silicon (Si) can influence Fe oxides’ chemical and physical properties but its role in GR formation and subsequent oxidative transformation have not been studied starting at initial nucleation. Green rust sulfate [GR(SO 4 )] and green rust carbonate [GR(CO 3 )] were both coprecipitated from salts by base titration in increasing % mol Si (0, 1, 10, and 50). The minerals were characterized before and after rapid (24 h) aqueous air-oxidation by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fe extended x-ray absorption fine structure spectroscopy (EXAFS), and N 2 -BET surface area. Results showed that only GR(SO4) or GR(CO3) was formed at every tested Si concentration. Increasing % mol Si caused decreased plate size and increased surface area in GR(CO3) but not GR(SO4). GR plate basal thickness was not changed at any condition indicating a lack of Si interlayering. Air oxidation of GR(SO4) at all % mol Si contents transformed by dissolution and reprecipitation into lepidocrocite and goethite, favoring ferrihydrite with higher % Si content. Air oxidation of GR(CO3) transformed into magnetite and goethite but increasing Si caused GR to oxidize while retaining its hexagonal plate structure via solid-state oxidation. Our results indicate that Si has the potential to cause GR to form in smaller particles and upon air oxidation, Si can either stabilize the plate structure or alter transformation to ferrihydrite.
KFe3(SO7)2 crystallizes in the trigonal R3m space group. The structure is three-dimensional. K is bonded to twelve O atoms to form KO12 cuboctahedra that share corners with six SO4 tetrahedra and faces with six equivalent FeO6 octahedra. There are a spread of K–O bond distances ranging from 2.89–3.18 Å. Fe is bonded to six O atoms to form FeO6 octahedra that share corners with four equivalent FeO6 octahedra, corners with two SO4 tetrahedra, and faces with two equivalent KO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 40–46°. There are a spread of Fe–O bond distances ranging from 1.84–2.11 Å. There are two inequivalent S sites. In the first S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with three equivalent KO12 cuboctahedra and corners with three equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 51°. There is one shorter (1.45 Å) and three longer (1.51 Å) S–O bond length. In the second S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with three equivalent KO12 cuboctahedra and corners with three equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There is one shorter (1.45 Å) and three longer (1.50 Å) S–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a single-bond geometry to one S atom. In the third O site, O is bonded in a 2-coordinate geometry to one K, one Fe, and one S atom. In the fourth O site, O is bonded in a 2-coordinate geometry to one K, one Fe, and one S atom. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to one K and two equivalent Fe atoms. In the sixth O site, O is bonded in a distorted bent 120 degrees geometry to one K and two equivalent Fe atoms.
FeZn(SO7)2O2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of four oxygen molecules and two FeZn(SO7)2 ribbons oriented in the (1, 0, 0) direction. In each FeZn(SO7)2 ribbon, there are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with four SO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Fe–O bond distances ranging from 2.01–2.07 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra and corners with two equivalent SO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Fe–O bond distances ranging from 1.80–1.99 Å. Zn is bonded in a trigonal planar geometry to three O atoms. There are a spread of Zn–O bond distances ranging from 1.86–2.02 Å. There are two inequivalent S sites. In the first S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with two FeO6 octahedra. The corner-sharing octahedra tilt angles range from 47–57°. There are a spread of S–O bond distances ranging from 1.44–1.53 Å. In the second S site, S is bonded to four O atoms to form SO4 tetrahedra that share a cornercorner with one FeO6 octahedra. The corner-sharing octahedral tilt angles are 35°. There are a spread of S–O bond distances ranging from 1.47–1.51 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a single-bond geometry to one Fe atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Fe and one S atom. In the fourth O site, O is bonded in a distorted bent 120 degrees geometry to one Zn and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a single-bond geometry to one S atom. In the sixth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.25 Å. In the seventh O site, O is bonded in a single-bond geometry to one S atom. In the eighth O site, O is bonded in a distorted bent 120 degrees geometry to one Fe and one S atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to two Fe atoms. In the tenth O site, O is bonded in a bent 150 degrees geometry to one Zn and one S atom. In the eleventh O site, O is bonded in a single-bond geometry to one Zn atom. In the twelfth O site, O is bonded in a bent 120 degrees geometry to one Fe and one S atom. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to two O atoms. In the fourteenth O site, O is bonded in a single-bond geometry to one S atom.
Na3Fe(SO4)3 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.34–3.02 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six equivalent O2- atoms to form FeO6 octahedra that share corners with six equivalent SO4 tetrahedra. All Fe–O bond lengths are 2.04 Å. In the second Fe3+ site, Fe3+ is bonded to six equivalent O2- atoms to form FeO6 octahedra that share corners with six equivalent SO4 tetrahedra. All Fe–O bond lengths are 2.00 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with two FeO6 octahedra. The corner-sharing octahedra tilt angles range from 33–45°. There are a spread of S–O bond distances ranging from 1.46–1.52 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Fe3+, and one S6+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Na1+ and one S6+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Na1+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+, one Fe3+, and one S6+ atom.
KFe3H6(SO7)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. K1+ is bonded to twelve O2- atoms to form KO12 cuboctahedra that share corners with six equivalent SO4 tetrahedra and faces with six equivalent FeO6 octahedra. There are six shorter (2.91 Å) and six longer (3.03 Å) K–O bond lengths. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent FeO6 octahedra, corners with two equivalent SO4 tetrahedra, and faces with two equivalent KO12 cuboctahedra. The corner-sharing octahedral tilt angles are 46°. There are four shorter (2.02 Å) and two longer (2.08 Å) Fe–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent KO12 cuboctahedra and corners with three equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There is one shorter (1.47 Å) and three longer (1.50 Å) S–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Fe3+, and one S6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one K1+, two equivalent Fe3+, and one H1+ atom.