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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on GdTi2CdO6F by Materials Project

GdTi2CdO6F crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Gd3+ is bonded to six O2- and two equivalent F1- atoms to form distorted GdO6F2 hexagonal bipyramids that share edges with two equivalent GdO6F2 hexagonal bipyramids, edges with four equivalent CdO6F2 hexagonal bipyramids, and edges with six TiO6 octahedra. There are four shorter (2.46 Å) and two longer (2.51 Å) Gd–O bond lengths. Both Gd–F bond lengths are 2.23 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra, edges with two equivalent GdO6F2 hexagonal bipyramids, and edges with four equivalent CdO6F2 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–48°. There is four shorter (1.98 Å) and two longer (2.01 Å) Ti–O bond length. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra, edges with two equivalent CdO6F2 hexagonal bipyramids, and edges with four equivalent GdO6F2 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 48–51°. There is two shorter (1.98 Å) and four longer (1.99 Å) Ti–O bond length. Cd2+ is bonded to six O2- and two equivalent F1- atoms to form distorted CdO6F2 hexagonal bipyramids that share edges with two equivalent CdO6F2 hexagonal bipyramids, edges with four equivalent GdO6F2 hexagonal bipyramids, and edges with six TiO6 octahedra. There are two shorter (2.51 Å) and four longer (2.59 Å) Cd–O bond lengths. Both Cd–F bond lengths are 2.21 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Gd3+, two Ti4+, and one Cd2+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Gd3+ and two equivalent Ti4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ti4+ and two equivalent Cd2+ atoms. F1- is bonded to two equivalent Gd3+ and two equivalent Cd2+ atoms to form corner-sharing FGd2Cd2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd2P3Cl by Materials Project

Cd2P3Cl crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a 4-coordinate geometry to three P1- and two equivalent Cl1- atoms. There are a spread of Cd–P bond distances ranging from 2.57–2.67 Å. There are one shorter (2.73 Å) and one longer (3.43 Å) Cd–Cl bond lengths. In the second Cd2+ site, Cd2+ is bonded in a 5-coordinate geometry to three P1- and two equivalent Cl1- atoms. There are a spread of Cd–P bond distances ranging from 2.57–2.67 Å. There are one shorter (2.72 Å) and one longer (3.42 Å) Cd–Cl bond lengths. There are three inequivalent P1- sites. In the first P1- site, P1- is bonded to two Cd2+ and two P1- atoms to form distorted corner-sharing PCd2P2 tetrahedra. Both P–P bond lengths are 2.21 Å. In the second P1- site, P1- is bonded to two equivalent Cd2+ and two P1- atoms to form distorted corner-sharing PCd2P2 trigonal pyramids. The P–P bond length is 2.20 Å. In the third P1- site, P1- is bonded to two equivalent Cd2+ and two P1- atoms to form distorted corner-sharing PCd2P2 trigonal pyramids. Cl1- is bonded in a distorted L-shaped geometry to four Cd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd2P3Cl by Materials Project

Cd2P3Cl crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Cd2+ is bonded in a 4-coordinate geometry to three P1- and two equivalent Cl1- atoms. There are a spread of Cd–P bond distances ranging from 2.57–2.67 Å. There are one shorter (2.72 Å) and one longer (3.43 Å) Cd–Cl bond lengths. There are two inequivalent P1- sites. In the first P1- site, P1- is bonded to two equivalent Cd2+ and two P1- atoms to form distorted corner-sharing PCd2P2 trigonal pyramids. There are one shorter (2.20 Å) and one longer (2.21 Å) P–P bond lengths. In the second P1- site, P1- is bonded to two equivalent Cd2+ and two equivalent P1- atoms to form distorted corner-sharing PCd2P2 tetrahedra. Cl1- is bonded in a distorted L-shaped geometry to four equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1981

A search for neutral hydrogen in D and cD galaxies

Recent X-ray spectroscopic results suggest that 2-3 solar masses/yr of cooling gas may be falling into M87 and as much as 300 solar masses/yr into giant galaxies in rich clusters. The eventual fate of the gas in the radiatively accreting flow is an open question. In an attempt to set some bounds on the evolution of the gas, a sensitive search was performed for H I in a sample of eight D and cD galaxies in rich and poor clusters. Null detections in all cases set upper limits of (4-20) x 10 to the 8th solar masses of H I in the giant galaxies. Possible reasons for these nondetections and alternative evolutionary fates for the accreting gas are discussed.

Burns, J. O.↗
DOE OSTI2020

Materials Data on Cd2AsO4F by Materials Project

Cd2AsO4F crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to four O2- and two equivalent F1- atoms to form distorted CdO4F2 pentagonal pyramids that share corners with two equivalent CdO4F2 octahedra, corners with four equivalent AsO4 tetrahedra, edges with two equivalent CdO4F2 octahedra, and edges with two equivalent CdO4F2 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 42–68°. There are a spread of Cd–O bond distances ranging from 2.24–2.40 Å. There are one shorter (2.30 Å) and one longer (2.61 Å) Cd–F bond lengths. In the second Cd2+ site, Cd2+ is bonded to four O2- and two equivalent F1- atoms to form distorted CdO4F2 octahedra that share corners with two equivalent CdO4F2 pentagonal pyramids, corners with four equivalent AsO4 tetrahedra, edges with two equivalent CdO4F2 octahedra, and edges with two equivalent CdO4F2 pentagonal pyramids. There are a spread of Cd–O bond distances ranging from 2.25–2.36 Å. There are one shorter (2.33 Å) and one longer (2.49 Å) Cd–F bond lengths. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four equivalent CdO4F2 octahedra and corners with four equivalent CdO4F2 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 48–59°. There is three shorter (1.72 Å) and one longer (1.73 Å) As–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cd2+ and one As5+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cd2+ and one As5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cd2+ and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cd2+ and one As5+ atom. F1- is bonded in a 4-coordinate geometry to four Cd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2CdCl4 by Materials Project

Na2CdCl4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six Cl1- atoms. There are a spread of Na–Cl bond distances ranging from 2.86–3.01 Å. Cd2+ is bonded to six Cl1- atoms to form edge-sharing CdCl6 octahedra. There are two shorter (2.62 Å) and four longer (2.71 Å) Cd–Cl bond lengths. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded to four equivalent Na1+ and one Cd2+ atom to form a mixture of distorted corner and edge-sharing ClNa4Cd trigonal bipyramids. In the second Cl1- site, Cl1- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd3SiO5 by Materials Project

Cd3SiO5 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. there are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are one shorter (2.17 Å) and four longer (2.31 Å) Cd–O bond lengths. In the second Cd2+ site, Cd2+ is bonded to six O2- atoms to form distorted CdO6 octahedra that share corners with two equivalent CdO6 octahedra, corners with four equivalent SiO4 tetrahedra, and edges with four equivalent CdO6 octahedra. The corner-sharing octahedral tilt angles are 25°. There are four shorter (2.35 Å) and two longer (2.51 Å) Cd–O bond lengths. Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with eight equivalent CdO6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Si–O bond lengths are 1.65 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to five Cd2+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2MnCdFe(PO4)3 by Materials Project

Na2MnFeCd(PO4)3 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (2.36 Å) and four longer (2.49 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.24–2.86 Å. In the third Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.92 Å. Mn2+ is bonded to six O2- atoms to form distorted MnO6 octahedra that share corners with two PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 2.10–2.45 Å. Fe3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Fe–O bond distances ranging from 1.91–2.48 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.48 Å) and two longer (2.66 Å) Cd–O bond lengths. In the second Cd2+ site, Cd2+ is bonded in a distorted linear geometry to two equivalent O2- atoms. Both Cd–O bond lengths are 2.10 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.48–1.51 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 43°. There is two shorter (1.55 Å) and two longer (1.57 Å) P–O bond length. In the third P5+ site, P5+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.53–1.69 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There is two shorter (1.51 Å) and two longer (1.62 Å) P–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Mn2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Fe3+, and one P5+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Na1+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Mn2+, and one O2- atom. The O–O bond length is 1.44 Å. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Mn2+, one Cd2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Mn2+, one Cd2+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Fe3+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Mn2+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Fe3+, and one O2- atom. In the eleventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Na1+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a trigonal planar geometry to one Mn2+, one Fe3+, and one Cd2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc2Cd3(GeO4)3 by Materials Project

Sc2Cd3(GeO4)3 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Sc3+ is bonded to six equivalent O2- atoms to form ScO6 octahedra that share corners with six equivalent GeO4 tetrahedra. All Sc–O bond lengths are 2.11 Å. Cd2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.43 Å) and four longer (2.58 Å) Cd–O bond lengths. Ge4+ is bonded to four equivalent O2- atoms to form GeO4 tetrahedra that share corners with four equivalent ScO6 octahedra. The corner-sharing octahedral tilt angles are 50°. All Ge–O bond lengths are 1.78 Å. O2- is bonded in a 4-coordinate geometry to one Sc3+, two equivalent Cd2+, and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn2Cd3(GeO4)3 by Materials Project

Mn2Cd3(GeO4)3 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Mn3+ is bonded to six equivalent O2- atoms to form MnO6 octahedra that share corners with six equivalent GeO4 tetrahedra. All Mn–O bond lengths are 2.05 Å. Cd2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.39 Å) and four longer (2.58 Å) Cd–O bond lengths. Ge4+ is bonded to four equivalent O2- atoms to form GeO4 tetrahedra that share corners with four equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 49°. All Ge–O bond lengths are 1.79 Å. O2- is bonded in a 4-coordinate geometry to one Mn3+, two equivalent Cd2+, and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd3Fe2(GeO4)3 by Materials Project

Fe2Cd3(GeO4)3 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent O2- atoms to form FeO6 octahedra that share corners with six equivalent GeO4 tetrahedra. All Fe–O bond lengths are 2.04 Å. Cd2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.39 Å) and four longer (2.58 Å) Cd–O bond lengths. Ge4+ is bonded to four equivalent O2- atoms to form GeO4 tetrahedra that share corners with four equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 48°. All Ge–O bond lengths are 1.79 Å. O2- is bonded in a 4-coordinate geometry to one Fe3+, two equivalent Cd2+, and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V2Cd3(GeO4)3 by Materials Project

V2Cd3(GeO4)3 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. V3+ is bonded to six equivalent O2- atoms to form VO6 octahedra that share corners with six equivalent GeO4 tetrahedra. All V–O bond lengths are 2.04 Å. Cd2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.40 Å) and four longer (2.58 Å) Cd–O bond lengths. Ge4+ is bonded to four equivalent O2- atoms to form GeO4 tetrahedra that share corners with four equivalent VO6 octahedra. The corner-sharing octahedral tilt angles are 48°. All Ge–O bond lengths are 1.79 Å. O2- is bonded in a 4-coordinate geometry to one V3+, two equivalent Cd2+, and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2Cd2O3 by Materials Project

K2Cd2O3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.72–3.31 Å. Cd2+ is bonded to four O2- atoms to form a mixture of edge and corner-sharing CdO4 tetrahedra. There are a spread of Cd–O bond distances ranging from 2.19–2.28 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent K1+ and two equivalent Cd2+ atoms to form corner-sharing OK4Cd2 octahedra. The corner-sharing octahedral tilt angles are 56°. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent K1+ and three equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Effect of Pressure on Trace Element Activity Coefficients in Metal-Silicate Systems

The partitioning of trace elements between metal and silicate melts serves as the foundation for understanding the differentiation of a planetary body into a metallic core and silicate mantle. Element activity influences metal-silicate partitioning behavior. Activity coefficients are directly dependent on composition and temperature, and can be indirectly dependent on oxygen fugacity and pressure. Distinguishing the effect of pressure from other variables on the activity coefficients and partitioning is important for understanding the chemical evolution of different planetary bodies during differentiation. In this study, we investigated the influence of pressure on the activity coefficients of Cu, Mo, Pd, Pt, As, Sb, and Bi in Fe-Si metallic liquids. All of these elements exhibit moderate to high activity coefficients in Fe-Si liquids at low pressure, which significantly controls their metal-silicate partitioning behavior. Identifying whether this strong dependence persists at higher pressures is critical to modeling and understanding the chemical consequences of core formation. New experiments at 10 GPa were used to derive activity coefficients for these metals which can be compared to activity coefficients determined at 1 GPa. Experiments were conducted at 10 GPa and 2373K using a 10/5 assembly in the 880-ton multi-anvil press at NASA Johnson Space Center. The standard 10/5 COMPRES assembly was slightly modified to accommodate a sample capsule machined from single-crystal MgO that minimizes melt percolation out of the sample volume during the experiment. Experiment starting materials were comprised of 70 wt.% Knippa basalt and 30 wt.% metal. The metal mixture (~85 wt.% Fe) was created by adding the elements of interest (Cu, Mo, Pd, Pt, As, Sb, Bi) to Fe metal powder. Varied amounts of Si metal (0-10 wt.% Si) were added to the metal-silicate mixtures to generate a systematic series of starting materials. For each element, an epsilon interaction parameter in Fe-Si liquid was derived from the results of our 0-10 wt.% Si metal series. To investigate whether pressure influences the trace element activity coefficients in the 1-10 GPa pressure range, we compared our results at 10 GPa to those at 1-4 GPa [1-3]. Our results can also be directly compared to interaction parameters for Au, P, V, Mn, Ga, Zn, Cd, Sn, W, Pb, and Nb previously determined at 10 GPa and 2373K following the same methods [4]. Combined, this suite of interaction parameters will directly inform metal-silicate partitioning between 1 and 10 GPa, and assess whether these values can be extrapolated to modeling differentiation processes at pressures >10 GPa.

Kelsey Prissel↗
NASA NTRSDate not supplied

Effect of Pressure and Oxidation State on Pnictogen Metal-Silicate Partitioning

The partitioning of trace elements between metal and silicate melts serves as the foundation for understanding the differentiation of a planetary body into a metallic core and silicate mantle. Element activity influences metal-silicate partitioning behavior. Activity coefficients are directly dependent on composition and temperature, and can be indirectly dependent on oxygen fugacity and pressure. Distinguishing the effect of pressure from other variables on the activity coefficients and partitioning is important for understanding the chemical evolution of different planetary bodies during differentiation. In this study, we investigated the influence of pressure on the activity coefficients of Cu, Mo, Pd, Pt, As, Sb, and Bi in Fe-Si metallic liquids. All of these elements exhibit moderate to high activity coefficients in Fe-Si liquids at low pressure, which significantly controls their metal-silicate partitioning behavior. Identifying whether this strong dependence persists at higher pressures is critical to modeling and understanding the chemical consequences of core formation. New experiments at 10 GPa were used to derive activity coefficients for these metals which can be compared to activity coefficients determined at 1 GPa. Experiments were conducted at 10 GPa and 2373K using a 10/5 assembly in the 880-ton multi anvil press at NASA Johnson Space Center. The standard 10/5 COMPRES assembly was slightly modified to accommodate a sample capsule machined from single-crystal MgO that minimizes melt percolation out of the sample volume during the experiment. Experiment starting materials were comprised of 70 wt.% Knippa basalt and 30 wt.% metal. The metal mixture (~85 wt.% Fe) was created by adding the elements of interest (Cu, Mo, Pd, Pt, As, Sb, Bi) to Fe metal powder. Varied amounts of Si metal (0-10 wt.% Si) were added to the metal-silicate mixtures to generate a systematic series of starting materials. For each element, an epsilon interaction parameter in Fe-Si liquid was derived from the results of our 0-10 wt.% Si metal series. To investigate whether pressure influences the trace element activity coefficients in the 1-10 GPa pressure range, we compared our results at 10 GPa to those at 1-4 GPa [1-3]. Our results can also be directly compared to interaction parameters for Au, P, V, Mn, Ga, Zn, Cd, Sn, W, Pb, and Nb previously determined at 10 GPa and 2373K following the same methods [4]. Combined, this suite of interaction parameters will directly inform metal- silicate partitioning between 1 and 10 GPa, and assess whether these values can be extrapolated to modeling differentiation processes at pressures >10 GPa. [1] Righter et al. (2018) GCA 232, 101-123 [2] Righter et al. (2019) MaPS 54, 1379-1394 [3] Steenstra et al. (2020) Icarus, 335, 113391 [4] Righter et al. (2020) Geochem. Persp. Let. 15, 44-49

Kelsey Prissel↗
DOE OSTI2022

Zinc speciation and desorption kinetics in a mining waste impacted tropical soil amended with phosphate

Mining is an important component of the Brazilian economy. However, it may also contribute to environmental problems such as the pollution of soils with zinc and other potentially toxic metals. Our objective was to evaluate changes in the chemical speciation and mobility of Zn in a soil amended with phosphate. Soil samples were collected from a deactivated mining area in the state of Minas Gerais, Brazil, and amended with NH 4 H 2 PO 4 saturated with deionized water to 70 % of maximum water retention and incubated at 25 ± 2 °C in open containers for 60 days. The soil was chemically and mineralogically characterized, and sequential extraction, desorption kinetics, and speciation were carried out using synchrotron bulk-sample and micro–X-ray Absorption Near-Edge Structure (XANES/μ-XANES) spectroscopy at the Zn K-edge, and X-ray fluorescence microprobe analysis (μ-XRF). The combination of μ-XRF and μ-XANES techniques made it possible to identify Zn hotspots in the main species formed after phosphate remediation. The best fit combination for bulk XANES and μ-XANES was observed in Zn-montmorillonite, Zn-kerolite, Zn-ferrihydrite, and gahnite. In the course of phosphate treatment, gahnite, Zn layered double hydroxides (Zn-LDH), Zn3(PO4), and ZnO were identified by bulk XANES, while Zn-ferrihydrite, Zn-montmorillonite, and scholzite were identified by μ-XANES. Zinc in the phosphate-amended soil had the strongest partial correlations (r' > 0.05) with Ni, Co, Fe, Cr, Mn, Si, P, Cd, Pb, and Cd, while the unamended soil showed the strongest correlation with Cu, Pb, Fe, and Si. The application of NH 4 H 2 PO 4 altered Zn speciation and favored an increase in Zn desorption. Here, the most available Zn contents after phosphate amendment were correlated with the release of exchangeable Zn fractions, associated with carbonate and organic matter.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on Nb2Cd2O7 by Materials Project

Cd2Nb2O7 crystallizes in the orthorhombic Ima2 space group. The structure is three-dimensional. there are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra and edges with six CdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 33–51°. There are a spread of Nb–O bond distances ranging from 1.90–2.15 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra and edges with six CdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 33–51°. There are a spread of Nb–O bond distances ranging from 1.91–2.12 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to eight O2- atoms to form distorted CdO8 hexagonal bipyramids that share edges with six CdO8 hexagonal bipyramids and edges with six NbO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.30–2.84 Å. In the second Cd2+ site, Cd2+ is bonded to eight O2- atoms to form distorted CdO8 hexagonal bipyramids that share edges with six CdO8 hexagonal bipyramids and edges with six NbO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.29–2.87 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Nb5+ and two Cd2+ atoms. In the second O2- site, O2- is bonded to four Cd2+ atoms to form corner-sharing OCd4 tetrahedra. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Nb5+ and two equivalent Cd2+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Nb5+ and two equivalent Cd2+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Nb5+ and two Cd2+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Chemical studies of H chondrites. 4: New data and comparison of Antarctic suites

We report data for the trace elements Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Ti, and In (ordered by putative volatility during nebular condensation and accretion) determined by neutron activation analysis in 13 H5 chondrites from Victoria Land and 20 H4-6 chondrites from Queen Maud Land, Antarctica. These and earlier results provide Antarctic sample suites of 34 chondrites from Victoria Land and 25 from Queen Maud Land. Treatment of data for the most volatile 10 elements (Rb to In) in these studies by multivariate statistical techniques more robust, as well as more conservative, than conventional linear discriminant analysis and logistic regression demonstrates that compositions differ at marginally significant levels. This difference cannot be explained by trivial (terrestrial) causes and becomes more significant, despite the smaller size of the database, when comparisons are limited to data from a single analyst and when all upper limits are eliminated from consideration. The Victoria Land and Queen Maud Land suites have different mean terrestrial ages (approximately 300 kyr and approximately 100 kyr, respectively) and age distributions, suggesting that a time-dependent variation of chondritic sources with different thermal histories is responsible. As a result, these two Antarctic suites are, on average, chemically distinguishable from each other. Since H chondrites serve as a paradigm for other meteorite classes, these results indicate that the near-Earth populations of planetary materials varied with time on the 10(exp 5)-year timescale.

Wolf, Stephen F.↗