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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on La3Bi3O11 by Materials Project

La3Bi3O11 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a body-centered cubic geometry to eight O2- atoms. All La–O bond lengths are 2.60 Å. In the second La3+ site, La3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.35–3.00 Å. Bi+4.33+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing BiO6 octahedra. The corner-sharing octahedral tilt angles are 64°. There are a spread of Bi–O bond distances ranging from 2.20–2.25 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two La3+ and two equivalent Bi+4.33+ atoms to form a mixture of distorted edge and corner-sharing OLa2Bi2 tetrahedra. In the second O2- site, O2- is bonded in a distorted water-like geometry to two equivalent La3+ and two equivalent Bi+4.33+ atoms. In the third O2- site, O2- is bonded to four La3+ atoms to form a mixture of distorted edge and corner-sharing OLa4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl2(SbO3)3 by Materials Project

Tl2(SbO3)3 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. Tl is bonded in a 6-coordinate geometry to six O atoms. There are three shorter (2.70 Å) and three longer (2.86 Å) Tl–O bond lengths. Sb is bonded to six O atoms to form a mixture of edge and corner-sharing SbO6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Sb–O bond distances ranging from 1.99–2.04 Å. There are two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Tl and two equivalent Sb atoms. In the second O site, O is bonded in a distorted trigonal planar geometry to one Tl and two equivalent Sb atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Planetary Nebulae in the MW, LMC, SMC: Results from FUSE and HST data

We use FUSE and HST data to study Planetary Nebulae (PN) systems in the Milky Way, LMC and SMC. Theoretically, metallicity affects several aspects of the post-AGB evolution, including mass-loss and the yield of processed material, which are important factors in the chemical evolution of galaxies. Therefore, it is very important to study PNe in different environments. In Bianchi's FUSE programs, we observed CSPN in the Milky Way (Cycle 1), LMC (Cycle 2) and SMC (Cyde 3), representing a range of metallicities from solar to 1/10th solar. The far-UV range reveals the spectrum of the central star (CSPN), uniquely enabling a direct estimate of the ionizing source parameters. Combined with archive HST data, these spectra provide a measurement of T(sub eff), log g, L(sub bol), abundances, wind velocity and mass-loss rate for these post-AGB stars. Additionally, these spectra provide a measurement of the circumstellar H2 and HI, which added to the mass of the central star and of the ionized shell allows us to test theoretical initial-final mass relations, and to put together a complete picture of the star's evolution.

Herald, J. E.↗
DOE OSTI2020

Materials Data on La3Pt3O11 by Materials Project

La3Pt3O11 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are two shorter (2.40 Å) and six longer (2.58 Å) La–O bond lengths. In the second La3+ site, La3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.34–2.83 Å. Pt+4.33+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing PtO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are four shorter (2.03 Å) and two longer (2.05 Å) Pt–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two La3+ and two equivalent Pt+4.33+ atoms to form distorted OLa2Pt2 trigonal pyramids that share corners with three equivalent OLa4 tetrahedra, corners with nine equivalent OLa2Pt2 trigonal pyramids, an edgeedge with one OLa4 tetrahedra, and edges with two equivalent OLa2Pt2 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted L-shaped geometry to two equivalent La3+ and two equivalent Pt+4.33+ atoms. In the third O2- site, O2- is bonded to four La3+ atoms to form OLa4 tetrahedra that share a cornercorner with one OLa4 tetrahedra, corners with nine equivalent OLa2Pt2 trigonal pyramids, edges with three equivalent OLa4 tetrahedra, and edges with three equivalent OLa2Pt2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La3Ir3O11 by Materials Project

La3Ir3O11 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are two shorter (2.40 Å) and six longer (2.58 Å) La–O bond lengths. In the second La3+ site, La3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.34–2.85 Å. Ir+4.33+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing IrO6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are four shorter (2.00 Å) and two longer (2.04 Å) Ir–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four La3+ atoms to form OLa4 tetrahedra that share a cornercorner with one OLa4 tetrahedra, corners with nine equivalent OLa2Ir2 trigonal pyramids, edges with three equivalent OLa4 tetrahedra, and edges with three equivalent OLa2Ir2 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted water-like geometry to two equivalent La3+ and two equivalent Ir+4.33+ atoms. In the third O2- site, O2- is bonded to two La3+ and two equivalent Ir+4.33+ atoms to form distorted OLa2Ir2 trigonal pyramids that share corners with three equivalent OLa4 tetrahedra, corners with nine equivalent OLa2Ir2 trigonal pyramids, an edgeedge with one OLa4 tetrahedra, and edges with two equivalent OLa2Ir2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2023

NGC 6302: The Tempestuous Life of a Butterfly

Abstract NGC 6302 (The Butterfly Nebula) is an extremely energetic and rapidly expanding bipolar planetary nebula (PN). If the central source is a single star, then its apparent location in an H-R diagram places it among the most massive, hottest, and presumably rapidly evolving of all central stars of PNe. Our proper motion study of NGC 6302, based on Hubble Space Telescope WFC3 images spanning 11 yr, has uncovered at least four different pairs of uniformly expanding internal lobes ejected at various times and orientations over the past two millennia at speeds ranging from 10–600 km s −1 . In addition, we find a pair of collimated off-axis flows in constant motion at ∼770 ± 100 km s −1 within which bright [Feii]feathersare conspicuous. Combining our results with those previously published, we find that the ensemble of flows has an ionized mass >0.1M ⊙ and its kinetic energy, between 10 46 and 10 48 erg, lies at the upper end of gravity-powered PNe ejection processes such as stellar mergers or mass accretion. We assemble our results into a plausible historical timeline of ejections from the nucleus and suggest that the ejections are powered by gravitational infall.

Astronomy & Astrophysics↗
NASA NTRS2004

EPIC Study of Two Enigmatic Sources: The Mouse and SNR 359.1-0.5

The objective of the original proposal was to observe the Mouse pulsar wind nebula (associated with PSR J1744-2958) and the nearby supernova remnant G359.1-0.5, where the pulsar was probably born, with the XMM-Newton observatory to study the properties of these objects. SNR G359.1-0.5 was accepted as a Category C target and has not been observed. The Mouse was observed on April 27,2003 for 52 ks. The image analysis has shown that the Mouse is extended in the East-West direction, possibly along the direction of the pulsar's proper motion. The spectrum of this pulsar wind nebula can be described as an absorbed power law with the photon index GAMMA = 1.9 plus or minus 0.1, effective hydrogen column density n(sub H) = (2.6 plus or minus 0.1) x 10(exp 22) per square centimeter, and flux F = 1.8 x 10(exp -11) erg per square centimeter per second in the 1-10 keV energy range. Based on the n(sub H) value, the distance to the source is about 5 kpc, which results in the luminosity 3.7 x 10(exp 34) erg per second. We conclude that PSR J1744-2958 and the Mouse are not physically associated with G359.1-0.5, which lies at a larger distance. In addition to the Mouse, we also detected two Low-Mass X-ray Binaries, SLX 1744-299 and 1744-300, in the EPIC MOS and PN fields of view. The latter of these objects showed a Type I X-ray burst during our observation, with a rise time of 5 s and decay time of 60 s. A very strong pileup during the burst made the analysis of the burst properties unreliable. The spectral analysis of the persistent radiation from SLX 1744-299 and 1744-300 yields the hydrogen column densities of 3.2 plus or minus 0.1 and (3.6 plus or minus 0.2) x 10(exp 22) per square centimeter, respectively, which suggests that the sources are close to the Galactic center (d = 8-9 kpc). The spectra can be reasonably well fitted with a blackbody plus thin disk model, with the blackbody temperatures of 1.7 plus or minus 0.2 and 1.8 plus or minus 0.2 keV, respectively.

Pavlov, George↗
DOE OSTI2020

Probing Few-Body Nuclear Dynamics via H 3 and He 3 ( e , e ' p ) pn Cross-Section Measurements

Here, we report the first measurement of the (e, e' p) three-body breakup reaction cross sections in helium-3 ( 3 He) and tritium ( 3 H) at large momentum transfer ($\langle{Q^2}\rangle$ ≈ 1.9 (GeV/c) 2 ) and x B > 1 kinematics, where the cross section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta 40 ≤ p miss ≤ 500 MeV/c that, in the QE limit with no rescattering, equals the initial momentum of the probed nucleon. The measured cross sections are compared with state-of-the-art ab-initio calculations. Overall good agreement, within ±20%, is observed between data and calculations for the full p miss range for 3 H and for 100 ≤ p miss ≤ 350 MeV/c for 3 He. Including the effects of rescattering of the outgoing nucleon improves agreement with the data at p miss > 250 MeV/c and suggests contributions from charge-exchange (SCX) rescattering. The isoscalar sum of 3 He plus 3 H, which is largely insensitive to SCX, is described by calculations to within the accuracy of the data over the entire pmiss range. This validates current models of the ground state of the three-nucleon system up to very high initial nucleon momenta of 500 MeV/c.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

The superatomic state beyond conventional magic numbers: Ligated metal chalcogenide superatoms

The field of cluster science is drawing increasing attention due to the strong size and composition-dependent properties of clusters and the exciting prospect of clusters serving as the building blocks for materials with tailored properties. However, identifying a unifying central paradigm that provides a framework for classifying and understanding the diverse behaviors is an outstanding challenge. One such central paradigm is the superatom concept that was developed for metallic and ligand-protected metallic clusters. The periodic electronic and geometric closed shells in clusters result in their properties being based on the stability they gain when they achieve closed shells. This stabilization results in the clusters having a well-defined valence allowing them to be classified as superatoms – thus, extending the periodic table to a third dimension. This perspective focuses on extending the superatomic concept to ligated metal-chalcogen clusters that have recently been synthesized in solutions and form assemblies with counterions that have wide-ranging applications. Here we illustrate that the periodic patterns emerge in the electronic structure of ligated metal-chalcogenide clusters. The stabilization gained by the closing of their electronic shells allows for the prediction of their redox properties. Further investigations reveal how the selection of ligands may control the redox properties of the superatoms. These ligated clusters may serve as chemical dopants for two-dimensional semiconductors to control their transport characteristics. Superatomic molecules of multiple metal-chalcogen superatoms allow for the formation of nano pn junctions ideal for directed transport and photon harvesting. As a result, the perspective outlines future developments, including the synthesis of magnetic superatoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YbH12(CN3)3 by Materials Project

YbH12(CN3)3 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded in an octahedral geometry to six equivalent N3- atoms. All Yb–N bond lengths are 2.45 Å. In the second Yb3+ site, Yb3+ is bonded in an octahedral geometry to six equivalent N3- atoms. All Yb–N bond lengths are 2.45 Å. C4+ is bonded in a trigonal planar geometry to three N3- atoms. There are a spread of C–N bond distances ranging from 1.34–1.38 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a 3-coordinate geometry to one Yb3+, one C4+, and one H1+ atom. The N–H bond length is 1.03 Å. In the second N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the third N3- site, N3- is bonded in a 3-coordinate geometry to one Yb3+, one C4+, and one H1+ atom. The N–H bond length is 1.02 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Geostationary Spectrograph (GeoSpec) for Earth and Atmospheric Science Applications

GeoSpec will support several possible future mission concepts in the Atmospheric Sciences and in Land and Ocean Sciences by measurement of both chemically linked atmospheric trace gas concentrations and profiles of important molecules such as OS, N02, CH20 and SO2 and at the same time coastal and ocean pollution events, tidal effects, and the origin and evolution of aerosol plumes. The instrument design concept we will describe is a dual spectrograph covering the WMS wavelength region of 310- 481 nm and the VIS/NIR wavelength region of 500-900 nm. A third channel in the short- wave infrared (SWIR) region between 2.2 p and 2.4 pn for total column measurements of CO, CH4, and N20 will also be described. The goal is to design a system capable of making moderate spatial resolution (750 meters at nadir) hyperspectral measurements (0.2 to 1.2 nm resolution) from a geostationary orbit. This would enable studies of time- varying pollution and coastal change processes with a temporal resolution of 5 minutes on a regional scale to 1 hour on a continental scale. Technological advances in the design and fabrication of convex holographic gratings and large format, high dynamic range PIN/CMOS detectors at the focal plane will be exploited. By simply changing the focal length of the front-end telescope GeoSpec can accommodate different orbital altitudes, including low Earth orbit, the Sun-side Lagrangian point L1, and/or different spatial resolutions.

Janz, Scott J.↗
NASA NTRS2006

Binary Black Hole Late Inspiral: Simulations for Gravitational Wave Observations

Coalescing binary black hole mergers are expected to be the strongest gravitational wave sources for ground-based interferometers, such as the LIGO, VIRGO, and GEO600, as well as the spacebased interferometer LISA. Until recently it has been impossible to reliably derive the predictions of General Relativity for the final merger stage, which takes place in the strong-field regime. Recent progress in numerical relativity simulations is, however, revolutionizing our understanding of these systems. We examine here the specific case of merging equal-mass Schwarzschild black holes in detail, presenting new simulations in which the black holes start in the late inspiral stage on orbits with very low eccentricity and evolve for approximately 1200M through approximately 7 orbits before merging. We study the accuracy and consistency of our simulations and the resulting gravitational waveforms, which encompass approximately 14 cycles before merger, and highlight the importance of using frequency (rather than time) to set the physical reference when comparing models. Matching our results to PN calculations for the earlier parts of the inspiral provides a combined waveform with less than half a cycle of accumulated phase error through the entire coalescence. Using this waveform, we calculate signal-to-noise ratios (SNRs) for iLIGO, adLIGO, and LISA, highlighting the contributions from the late-inspiral and merger-ringdown parts of the waveform which can now be simulated numerically. Contour plots of SNR as a function of z and M show that adLIGO can achieve SNR 2 10 for some IMBBHs out to z approximately equals 1, and that LISA can see MBBHs in the range 3 x 10(exp 4) approximately < M/Mo approximately < 10(exp 7) at SNR > 100 out to the earliest epochs of structure formation at z > 15.

Baker, John G.↗
DOE OSTI2020

Materials Data on K5YCo2(NO2)12 by Materials Project

K5YCo2(NO2)12 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to twelve O2- atoms to form KO12 cuboctahedra that share faces with two equivalent YO12 cuboctahedra and faces with six equivalent KO12 cuboctahedra. There are six shorter (2.79 Å) and six longer (2.85 Å) K–O bond lengths. In the second K1+ site, K1+ is bonded to twelve O2- atoms to form KO12 cuboctahedra that share edges with two equivalent YO12 cuboctahedra, edges with four equivalent KO12 cuboctahedra, and faces with four equivalent KO12 cuboctahedra. There are a spread of K–O bond distances ranging from 2.98–3.17 Å. Y3+ is bonded to twelve equivalent O2- atoms to form YO12 cuboctahedra that share edges with six equivalent KO12 cuboctahedra and faces with four equivalent KO12 cuboctahedra. All Y–O bond lengths are 2.77 Å. Co2+ is bonded in a distorted octahedral geometry to six equivalent N3+ atoms. All Co–N bond lengths are 1.94 Å. N3+ is bonded in a distorted bent 120 degrees geometry to one Co2+ and two O2- atoms. There is one shorter (1.25 Å) and one longer (1.28 Å) N–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one N3+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two K1+, one Y3+, and one N3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K5CeCo2(NO2)12 by Materials Project

K5CeCo2(NO2)12 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to twelve O2- atoms to form KO12 cuboctahedra that share faces with two equivalent CeO12 cuboctahedra and faces with six equivalent KO12 cuboctahedra. There are six shorter (2.80 Å) and six longer (2.85 Å) K–O bond lengths. In the second K1+ site, K1+ is bonded to twelve O2- atoms to form KO12 cuboctahedra that share edges with two equivalent CeO12 cuboctahedra, edges with four equivalent KO12 cuboctahedra, and faces with four equivalent KO12 cuboctahedra. There are a spread of K–O bond distances ranging from 2.99–3.14 Å. Ce3+ is bonded to twelve equivalent O2- atoms to form CeO12 cuboctahedra that share edges with six equivalent KO12 cuboctahedra and faces with four equivalent KO12 cuboctahedra. All Ce–O bond lengths are 2.84 Å. Co2+ is bonded in a distorted octahedral geometry to six equivalent N3+ atoms. All Co–N bond lengths are 1.95 Å. N3+ is bonded in a distorted bent 120 degrees geometry to one Co2+ and two O2- atoms. There is one shorter (1.25 Å) and one longer (1.28 Å) N–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one N3+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two K1+, one Ce3+, and one N3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KIrO3 by Materials Project

KIrO3 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are three shorter (2.71 Å) and three longer (2.90 Å) K–O bond lengths. In the second K1+ site, K1+ is bonded in a hexagonal planar geometry to six equivalent O2- atoms. All K–O bond lengths are 2.63 Å. Ir5+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing IrO6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are a spread of Ir–O bond distances ranging from 1.96–2.01 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two K1+ and two equivalent Ir5+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two equivalent Ir5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KSbO3 by Materials Project

KSbO3 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six equivalent O2- atoms. All K–O bond lengths are 2.66 Å. In the second K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are three shorter (2.71 Å) and three longer (2.93 Å) K–O bond lengths. Sb5+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing SbO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Sb–O bond distances ranging from 2.00–2.05 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two equivalent Sb5+ atoms. In the second O2- site, O2- is bonded to two K1+ and two equivalent Sb5+ atoms to form a mixture of distorted edge and corner-sharing OK2Sb2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KBiO3 by Materials Project

KBiO3 crystallizes in the cubic Pn-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six equivalent O2- atoms. All K–O bond lengths are 2.75 Å. In the second K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are three shorter (2.75 Å) and three longer (3.06 Å) K–O bond lengths. Bi5+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing BiO6 octahedra. The corner-sharing octahedral tilt angles are 54°. There are a spread of Bi–O bond distances ranging from 2.13–2.18 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two equivalent Bi5+ atoms. In the second O2- site, O2- is bonded to two K1+ and two equivalent Bi5+ atoms to form a mixture of distorted corner and edge-sharing OK2Bi2 tetrahedra.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Optimized silicon solar cells for space exploration power systems

A program is described aimed at designing and fabricating improved silicon solar cells for a range of missions extending from 0.1 to 15 astronomical units (Mercury to Jupiter). For missions lying inside Earth radius (Mercury, Venus) the major cell property required was very low series resistance, allowing high curve fill factor to be maintained at the higher intensities. For the Mercury mission, the temperature of the cell had to be kept low. This was achieved by reflecting more of the incident sunlight by use of large area front contacts. For the outer missions (Mars, the Asteroid belts and Jupiter) the formation of a Schottky barrier at the back contact had to be avoided (by use of a P+ layer under the back contact) and the excess leakage current of the PN junction had to be reduced. Optimum grid patterns were also derived and used for these missions.

Iles, P. A.↗