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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Deliberate Construction of Polyoxoniobates Exploiting the Carbonate Ligand

Abstract Polyoxometalates (POMs, metals=V V , Nb V , Ta V , Mo VI , W VI ) are molecular metal oxides that can be isolated without capping ligands. The high negative charge of polyoxoniobates (PONb) provides strong interactions with heterocations, advantageous for electrostatic assembly of modular materials. In four single‐crystal X‐ray structures, we demonstrate that carbonate combined with the very reactive decaniobate [Nb 10 O 28 ] 6− reassembles into a new decaniobate, [Nb 10 O 25 (CO 3 ) 6 ] 12− , featuring three carbonate‐ligated Nb‐polyhedra. These Nb‐sites can be replaced by heterometals (lanthanides), and the tridentate carbonate can serve as an anchor point to build niobate‐frameworks. Small‐angle X‐ray scattering and two additional X‐ray structures reveal that the reaction pathway proceeds through a Nb 24 ‐PONb intermediate, and the obtained PONb (with or without carbonate) is counterion, temperature, and solvent‐dependent (water or mixed water‐methanol). This provides an uncommon level of control for PONb chemistry.

Amiri, Mehran↗
DOE OSTI2020

Materials Data on TbCu(WO4)2 by Materials Project

TbCu(WO4)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tb–O bond distances ranging from 2.29–2.84 Å. In the second Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Tb–O bond distances ranging from 2.28–2.61 Å. In the third Tb3+ site, Tb3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tb–O bond distances ranging from 2.28–2.72 Å. There are six inequivalent W6+ sites. In the first W6+ site, W6+ is bonded to six O2- atoms to form distorted edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 1.80–2.20 Å. In the second W6+ site, W6+ is bonded to six O2- atoms to form distorted edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 1.80–2.21 Å. In the third W6+ site, W6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 1.80–2.30 Å. In the fourth W6+ site, W6+ is bonded to six O2- atoms to form distorted edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 1.81–2.21 Å. In the fifth W6+ site, W6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 1.81–2.28 Å. In the sixth W6+ site, W6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 1.80–2.26 Å. There are four inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.85 Å. In the second Cu1+ site, Cu1+ is bonded in a distorted square co-planar geometry to four O2- atoms. There are two shorter (1.87 Å) and two longer (2.46 Å) Cu–O bond lengths. In the third Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to three O2- atoms. There are a spread of Cu–O bond distances ranging from 1.85–2.58 Å. In the fourth Cu1+ site, Cu1+ is bonded in a distorted linear geometry to four O2- atoms. There are a spread of Cu–O bond distances ranging from 1.86–2.75 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Tb3+ and two equivalent W6+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Tb3+ and two W6+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Tb3+ and two equivalent W6+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Tb3+ and two W6+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Tb3+ and two W6+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two W6+ and one Cu1+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Tb3+, one W6+, and one Cu1+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Tb3+ and one W6+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Tb3+ and one W6+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Tb3+ and one W6+ atom. In the eleventh O2- site, O2- is bonded in a 2-coordinate geometry to one Tb3+, one W6+, and one Cu1+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Tb3+, two W6+, and one Cu1+ atom. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to two W6+ and one Cu1+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to two W6+ and one Cu1+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one W6+ atom. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Tb3+, one W6+, and one Cu1+ atom. In the seventeenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Tb3+ and two W6+ atoms. In the eighteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Tb3+ and one W6+ atom. In the nineteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Tb3+, two W6+, and one Cu1+ atom. In the twentieth O2- site, O2- is bonded in a 1-coordinate geometry to one Tb3+, one W6+, and one Cu1+ atom. In the twenty-first O2- site, O2- is bonded in a 4-coordinate geometry to one Tb3+, two W6+, and one Cu1+ atom. In the twenty-second O2- site, O2- is bonded in a bent 120 degrees geometry to one Tb3+ and one W6+ atom. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one W6+ atom. In the twenty-fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one W6+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2017

The Effect of the Spin-Forbidden Co((sup 1) Sigma plus) plus O((sup 3) P) Yields CO2 (1 Sigma (sub G) plus) Recombination Reaction on Afterbody Heating of Mars Entry Vehicles

Vibrationally excited CO2, formed by two-body recombination from CO((sup 1) sigma plus) and O((sup 3) P) in the wake behind spacecraft entering the Martian atmosphere reaction, is potentially responsible for the higher than anticipated radiative heating of the backshell, compared to pre-flight predictions. This process involves a spin-forbidden transition of the transient triplet CO2 molecule to the longer-lived singlet. To accurately predict the singlet-triplet transition probability and estimate the thermal rate coefficient of the recombination reaction, ab initio methods were used to compute the first singlet and three lowest triplet CO2 potential energy surfaces and the spin-orbit coupling matrix elements between these states. Analytical fits to these four potential energy surfaces were generated for surface hopping trajectory calculations, using Tully's fewest switches surface hopping algorithm. Preliminary results for the trajectory calculations are presented. The calculated probability of a CO((sup 1) sigma plus) and O((sup 3) P) collision leading to singlet CO2 formation is on the order of 10 (sup -4). The predicted flowfield conditions for various Mars entry scenarios predict temperatures in the range of 1000 degrees Kelvin - 4000 degrees Kelvin and pressures in the range of 300-2500 pascals at the shoulder and in the wake, which is consistent with a heavy-particle collision frequency of 10 (sup 6) to 10 (sup 7) per second. Owing to this low collision frequency, it is likely that CO((sup 1) sigma plus) molecules formed by this mechanism will mostly be frozen in a highly nonequilibrium rovibrational energy state until they relax by photoemission.

CO2 recombination↗
DOE OSTI2024

Elucidating the degradation mechanisms of Pt-free anode anion-exchange membrane fuel cells after durability testing

The development of anion-exchange membrane fuel cells (AEMFCs) has recently accelerated due to synergistic improvements yielding highly conductive membranes, stable ionomers, and enhanced alkaline electrocatalysts. However, cell durability, especially under realistic conditions, still poses a major challenge. Herein, we employ low-loadings of Pt-free Pd-based catalysts in the anode of AEMFCs and elucidate potential degradation mechanisms impacting long-term performance under conditions analogous to the real-world (high current density, H 2 –air (albeit CO 2 -free), and intermittent operation). Our high-performing AEMFCs achieve impressive performance with power densities approaching 1 W cm —2 and current densities up to 3.5 A cm —2 . Over a 200 h period of continuous operation in H 2 –air at a current density of 600 mA cm —2 , our model Pd/C–CeO 2 anode cell exhibits record stability (~30 μV h —1 degradation) compared to the literature and up to 6× better stability than our Pd/C and commercial Pt/C anode cells. Following an 8 h shutdown, the Pd/C–CeO 2 anode cell was restarted and continued for an additional 300 h with a higher degradation rate of ~600 μV h —1 . Thorough in situ evaluations and post-stability analyses provide insights into potential degradation mechanisms to be expected during extended operation under more realistic conditions and provide mitigation strategies to enable the widespread development of highly durable AEMFCs.

08 HYDROGEN↗
DOE OSTI2020

Materials Data on Ca2WO5 by Materials Project

Ca2WO5 crystallizes in the orthorhombic Ima2 space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.28–2.70 Å. W6+ is bonded to six O2- atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of W–O bond distances ranging from 1.87–2.08 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a square co-planar geometry to four equivalent Ca2+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ca2+ and one W6+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent W6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Multi-model analysis of the impact of water vapor on the radiative forcing of volcanic aerosols after the 2022 Hunga Eruption

On 15 January 2022, the Hunga volcano eruption released unprecedented amounts of water vapor into the atmosphere alongside a modest amount of SO 2 . In this work we analyse results from multiple Earth system models as part of the Hunga Tonga-Hunga Ha'apai Volcano Impact Model Observation Comparison Project. Our results show a good model agreement over the climatic outcomes of the eruption, overall indicating a significant negative radiative forcing from the Hunga eruption. The multi-model mean of global instantaneous radiative forcing averaged over 2022–2023 is estimated at −0.19 ± 0.06 W m −2 at the top-of-atmosphere (TOA), and −0.16 ± 0.06 W m −2 at the surface. Simulations with free-running meteorology and climatological sea surface temperatures and sea ice yield a global mean TOA forcing of −0.14 ± 0.10 W m −2 across two models for the first 2 years, decreasing to −0.09 ± 0.10 W m −2 on average between 2022 and 2027. However, these global values may be underestimated by about 50 %, considering that recent SO 2 injection retrievals suggest nearly twice the amount than the 0.5 Tg-SO 2 used in the protocol. We also find that the contribution from added stratospheric water vapor is minimal and that the injected SO 2 and the resulting formation of stratospheric sulfate dominate the radiative forcing. However, water vapor played a key role in the initial aerosol growth, leading to a stronger negative radiative forcing during the first 6 months after the eruption compared to simulations without water vapor co-injection.

Geosciences↗
DOE OSTI2023

G 0 W 0 Ionization Potentials of First-Row Transition Metal Aqua Ions

Here, we report computations of the vertical ionization potentials within the GW approximation of the near-complete series of first-row transition metal (V–Cu) aqua ions in their most common oxidation states, i.e., V 3+ , Cr 3+ , Cr 2+ , Mn 2+ , Fe 3+ , Fe 2+ , Co 2+ , Ni 2+ , and Cu 2+ . The d-orbital occupancy of these systems spans a broad range from d 2 to d 9 . All of the structures were first optimized at the density functional theory level using a large cluster of explicit water molecules that are embedded in a continuum solvation model. Vertical ionization potentials were computed with the one-shot G 0 W 0 approach on a range of transition metal ion clusters (6, 18, 40, and 60 explicit water molecules), wherein the convergence with respect to the basis set size was evaluated using the systems with 40 water molecules. We assess the results using three different density functional approximations as starting points for the vertical ionization potential calculations, namely, G 0 W 0 @PBE, G 0 W 0 @PBE0, and G 0 W 0 @r 2 SCAN. While the predicted ground-state structures are similar to all three exchange-correlation functionals, the vertical ionization potentials were in closer agreement with experiment when using the G 0 W 0 @PBE0 and G 0 W 0 @r 2 SCAN approaches, with the r 2 SCAN-based calculations being significantly less expensive. Computed bond distances and vertical ionization potentials for all structures are in good agreement with available experimental data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Kinetic and mechanistic analysis of a synthetic reversible CO 2 /HCO 2 - electrocatalyst

[Pt(depe) 2 ](PF 6 ) 2 electrocatalyzes the reversible conversion between CO 2 and HCO 2 - with high selectivity and low overpotential but low rates. A comprehensive kinetic analysis indicates the rate determining step for CO 2 reduction is the reactivity of a Pt hydride intermediate to produce HCO 2 - . To accelerate catalysis, the use of cationic and hydrogen-bond donor additives are explored.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Chemical and physical studies of type 3 chondrites. II Thermoluminescence of sixteen type 3 ordinary chondrites and relationships with oxygen isotopes

Thermoluminescence (TL) sensitivity values for sixteen type 3 ordinary chondrites, fourteen of them from Antarctica, have been measured. The values obtained (normalized to the TL sensitivity of the Dhajala meteorite) range from 1.6 (Allan Hills A77216) to 0.010 (Allan Hills A77176), and include two (Reckling Peak A80207 and Allan Hills A77176) that are particularly low. They fill a hiatus in the TL distribution that previously existed between St. Mary's County and Bishunpur, the latter being a meteorite with one of the lowest TL sensitivities known. The histogram of TL sensitivity values now shows a single distribution with higher values preferred; it resembles the histogram for L chondrites occupying the petrologic types 3, 4, 5, and 6. There is a tendency for the TL sensitivity of meteorites to decrease as delta O-18 increases. Theoretically, it is possible that the range of delta O-18 values observed may reflect progressive loss of O in the form of CO at very low temperatures, but very restrictive physical conditions and a complex history seem to be required.

Sears, D. W. G.↗
NASA NTRS1986

The effects of tantalum on the microstructure of two polycrystalline nickel-base superalloys - B-1900 + Hf and MAR-M247

The effect of changing the content of Ta on the gamma/gamma-prime carbide microstructure was investigated in two crystalline nickel-base superalloys: conventionally cast B-1900 + Hf, and both conventionally cast and directionally solidified MAR-M247. The changes occurring in the microstructure effects were similar in both alloys. The gamma-prime and carbide volume fractions increased linearly with Ta additions, while the gamma-prime phase compositions did not change. Bulk Ta additions increased the levels of Cr and Co (in addition to that of Ta) of the gamma phase, a result of the approximately constant partitioning ratios for these two elements. The addition of Ta led to a partial replacement of Hf in the MC carbides. In addition, Cr-rich M(23)C(6) carbides formed as a result of MC carbide decomposition during heat treatment.

Heckel, R. W.↗
DOE OSTI2020

Materials Data on Na3W2N5 by Materials Project

Na3W2N5 is Chalcostibite-like structured and crystallizes in the tetragonal I4_1 space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five N3- atoms. There are a spread of Na–N bond distances ranging from 2.48–2.77 Å. In the second Na1+ site, Na1+ is bonded in a distorted trigonal non-coplanar geometry to three N3- atoms. There are a spread of Na–N bond distances ranging from 2.35–2.61 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six N3- atoms. There are a spread of Na–N bond distances ranging from 2.52–2.96 Å. In the fourth Na1+ site, Na1+ is bonded in a square co-planar geometry to four N3- atoms. There are two shorter (2.36 Å) and two longer (2.41 Å) Na–N bond lengths. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded to four N3- atoms to form corner-sharing WN4 tetrahedra. There are a spread of W–N bond distances ranging from 1.77–1.98 Å. In the second W6+ site, W6+ is bonded to four N3- atoms to form corner-sharing WN4 tetrahedra. There are a spread of W–N bond distances ranging from 1.78–1.94 Å. There are five inequivalent N3- sites. In the first N3- site, N3- is bonded in a rectangular see-saw-like geometry to three Na1+ and one W6+ atom. In the second N3- site, N3- is bonded to four Na1+ and one W6+ atom to form distorted NNa4W trigonal bipyramids that share corners with two equivalent NNa4W trigonal bipyramids, corners with three equivalent NNa2W2 trigonal pyramids, and an edgeedge with one NNa4W trigonal bipyramid. In the third N3- site, N3- is bonded in a 2-coordinate geometry to two Na1+ and two equivalent W6+ atoms. In the fourth N3- site, N3- is bonded in a 4-coordinate geometry to two Na1+ and two equivalent W6+ atoms. In the fifth N3- site, N3- is bonded to two Na1+ and two W6+ atoms to form distorted NNa2W2 trigonal pyramids that share corners with three equivalent NNa4W trigonal bipyramids and a cornercorner with one NNa2W2 trigonal pyramid.

36 MATERIALS SCIENCE↗
NASA NTRS1999

Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

Non-NASA Center↗
DOE OSTI2020

Materials Data on Al3W3C4 by Materials Project

W3Al2C4Al crystallizes in the orthorhombic Pmm2 space group. The structure is two-dimensional and consists of one aluminum molecule and one W3Al2C4 sheet oriented in the (0, 0, 1) direction. In the W3Al2C4 sheet, there are three inequivalent W+2.33+ sites. In the first W+2.33+ site, W+2.33+ is bonded in an L-shaped geometry to two equivalent C4- atoms. Both W–C bond lengths are 2.16 Å. In the second W+2.33+ site, W+2.33+ is bonded to six C4- atoms to form a mixture of distorted edge, face, and corner-sharing WC6 pentagonal pyramids. There are two shorter (2.19 Å) and four longer (2.24 Å) W–C bond lengths. In the third W+2.33+ site, W+2.33+ is bonded to six C4- atoms to form distorted WC6 pentagonal pyramids that share corners with four equivalent AlC6 pentagonal pyramids, corners with eight WC6 pentagonal pyramids, edges with two equivalent AlC6 pentagonal pyramids, edges with four WC6 pentagonal pyramids, and faces with two equivalent WC6 pentagonal pyramids. There are two shorter (2.15 Å) and four longer (2.21 Å) W–C bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six C4- atoms to form distorted AlC6 pentagonal pyramids that share corners with four equivalent WC6 pentagonal pyramids, corners with four equivalent AlC6 pentagonal pyramids, edges with two equivalent WC6 pentagonal pyramids, edges with two equivalent AlC6 pentagonal pyramids, and faces with two equivalent AlC6 pentagonal pyramids. There are four shorter (2.17 Å) and two longer (2.36 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded in a distorted square co-planar geometry to four equivalent C4- atoms. All Al–C bond lengths are 2.11 Å. There are four inequivalent C4- sites. In the first C4- site, C4- is bonded to six W+2.33+ atoms to form a mixture of distorted edge, face, and corner-sharing CW6 pentagonal pyramids. In the second C4- site, C4- is bonded to six W+2.33+ atoms to form a mixture of distorted edge, face, and corner-sharing CW6 pentagonal pyramids. In the third C4- site, C4- is bonded in a 6-coordinate geometry to two equivalent W+2.33+ and four equivalent Al3+ atoms. In the fourth C4- site, C4- is bonded in a 6-coordinate geometry to six Al3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2007

A Luminosity Function of Ly(alpha)-Emitting Galaxies at Z [Approx. Equal to] 4.5(Sup 1),(Sup 2)

We present a catalog of 59 z [approx. equal to] 4:5 Ly(alpha)-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Are (LALA) narrowband imaging survey.We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of approx.76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z [approx. equal to] 4:5 Ly(alpha)- emitting galaxies in the [approx. equal to] 0.7 deg(exp 2) covered by the LALA imaging. As with the Keck LRIS sample, we find that a nonnegligible fraction of the co rest-frame equivalent widths (W(sub lambda)(sup rest)) that exceed the maximum predicted for normal stellar populations: 17%-31%(93%confidence) of the detected galaxies show (W(sub lambda)(sup rest)) 12%-27% (90% confidence) show (W(sub lambda)(sup rest)) > 240 A. We construct a luminosity function of z [approx. equal to] 4.5 Ly(alpha) emission lines for comparison to Ly(alpha) luminosity function < 6.6. We find no significant evidence for Ly(alpha) luminosity function evolution from z [approx. equal to] 3 to z [approx. equal to] 6. This result supports the conclusion that the intergalactic me largely reionized from the local universe out to z [approx. equal to] 6.5. It is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z approx. 3 an z approx. 6 in continuum-selected Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations.

cosmology↗
NASA NTRS1972

Mariner 9 ultraviolet spectrometer experiment - Initial results.

The UV airglow spectrum of Mars has been measured from an orbiting spacecraft during a 30-day period in November and December 1971. Significant variations in the scale height of the CO Cameron band airglow have been observed during a period of variable solar activity. The atomic oxygen and hydrogen airglow lines are present during all the observations. Measurements of the reflectance of the lower atmosphere of Mars show the spectral characteristics of particle scattering and a magnitude that is about 50% of that measured during the Mariner 6 and 7 experiments in 1969.

Barth, C. A.↗
DOE OSTI2020

Materials Data on Na4RhW5O26 by Materials Project

Na4W5RhO26 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are five inequivalent Na sites. In the first Na site, Na is bonded in a 6-coordinate geometry to seven O atoms. There are a spread of Na–O bond distances ranging from 2.39–3.06 Å. In the second Na site, Na is bonded in a distorted square co-planar geometry to four O atoms. There are two shorter (2.34 Å) and two longer (2.57 Å) Na–O bond lengths. In the third Na site, Na is bonded in a square co-planar geometry to four O atoms. There are two shorter (2.32 Å) and two longer (2.53 Å) Na–O bond lengths. In the fourth Na site, Na is bonded in a 6-coordinate geometry to seven O atoms. There are a spread of Na–O bond distances ranging from 2.43–3.10 Å. In the fifth Na site, Na is bonded in a distorted see-saw-like geometry to four O atoms. There are a spread of Na–O bond distances ranging from 2.26–2.56 Å. There are five inequivalent W sites. In the first W site, W is bonded in a 6-coordinate geometry to six O atoms. There are a spread of W–O bond distances ranging from 1.76–2.41 Å. In the second W site, W is bonded in a 6-coordinate geometry to six O atoms. There are a spread of W–O bond distances ranging from 1.76–2.37 Å. In the third W site, W is bonded in a 6-coordinate geometry to six O atoms. There are a spread of W–O bond distances ranging from 1.77–2.38 Å. In the fourth W site, W is bonded to six O atoms to form distorted WO6 octahedra that share a cornercorner with one RhO5 square pyramid. There are a spread of W–O bond distances ranging from 1.80–2.31 Å. In the fifth W site, W is bonded in a 6-coordinate geometry to six O atoms. There are a spread of W–O bond distances ranging from 1.80–2.23 Å. Rh is bonded to five O atoms to form distorted RhO5 square pyramids that share a cornercorner with one WO6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Rh–O bond distances ranging from 1.76–2.01 Å. There are twenty-six inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two Na and one O atom. The O–O bond length is 1.28 Å. In the second O site, O is bonded in a 3-coordinate geometry to two Na and one O atom. The O–O bond length is 1.27 Å. In the third O site, O is bonded in a 3-coordinate geometry to two Na and one O atom. In the fourth O site, O is bonded in an L-shaped geometry to one Na and one O atom. In the fifth O site, O is bonded in a distorted trigonal planar geometry to one Na, one W, and one Rh atom. In the sixth O site, O is bonded in a distorted trigonal planar geometry to one Na, one W, and one Rh atom. In the seventh O site, O is bonded in a distorted trigonal planar geometry to two equivalent Na and one W atom. In the eighth O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the ninth O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the tenth O site, O is bonded in a single-bond geometry to one Rh atom. In the eleventh O site, O is bonded in a bent 150 degrees geometry to one Na and one W atom. In the twelfth O site, O is bonded in a linear geometry to one Na and one W atom. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the fourteenth O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the fifteenth O site, O is bonded in a single-bond geometry to one Na atom. In the sixteenth O site, O is bonded in a 2-coordinate geometry to two Na atoms. In the seventeenth O site, O is bonded in a distorted trigonal planar geometry to one Na, one W, and one Rh atom. In the eighteenth O site, O is bonded in a distorted trigonal planar geometry to one Na, one W, and one Rh atom. In the nineteenth O site, O is bonded in a bent 150 degrees geometry to one Na and one W atom. In the twentieth O site, O is bonded in a distorted trigonal planar geometry to two Na and one W atom. In the twenty-first O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the twenty-second O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the twenty-third O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the twenty-fourth O site, O is bonded in a bent 120 degrees geometry to two W atoms. In the twenty-fifth O site, O is bonded in a square pyramidal geometry to five W atoms. In the twenty-sixth O site, O is bonded in a single-bond geometry to one Na atom.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Cloud draft structure and trace gas transport

During the second Amazon Boundary Layer Experiment (ABLE 2B), meteorological observations, chemical measurements, and model simulations are utilized in order to interpret convective cloud draft structure and to analyze its role in transport and vertical distribution of trace gases. One-dimensional photochemical model results suggest that the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production and the results of a two-dimensional time-dependent cloud model simulation are presented for the May 6, 1987 squall system. The mesoscale convective system exhibited evidence of significant midlevel detrainment in addition to transports to anvil heights. Chemical measurements of O3 and CO obtained in the convective environment are used to predict photochemical production within the troposphere and to corroborate the cloud model results.

Scala, John R.↗