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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Th(Re2Si)2 by Materials Project

Th(Re2Si)2 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Th is bonded in a 7-coordinate geometry to ten Re and seven Si atoms. There are a spread of Th–Re bond distances ranging from 3.29–3.52 Å. There are a spread of Th–Si bond distances ranging from 3.12–3.18 Å. There are four inequivalent Re sites. In the first Re site, Re is bonded in a 12-coordinate geometry to two equivalent Th, eight Re, and two equivalent Si atoms. There are a spread of Re–Re bond distances ranging from 2.62–2.98 Å. Both Re–Si bond lengths are 2.52 Å. In the second Re site, Re is bonded in a 12-coordinate geometry to three equivalent Th, six Re, and three Si atoms. There are a spread of Re–Re bond distances ranging from 2.61–2.77 Å. There are one shorter (2.49 Å) and two longer (2.60 Å) Re–Si bond lengths. In the third Re site, Re is bonded in a 12-coordinate geometry to two equivalent Th, eight Re, and three Si atoms. There are one shorter (2.73 Å) and two longer (2.90 Å) Re–Re bond lengths. There are a spread of Re–Si bond distances ranging from 2.48–3.04 Å. In the fourth Re site, Re is bonded to three equivalent Th, six Re, and three equivalent Si atoms to form distorted face-sharing ReTh3Re6Si3 cuboctahedra. There are one shorter (2.46 Å) and two longer (2.54 Å) Re–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four equivalent Th, five Re, and one Si atom. The Si–Si bond length is 2.61 Å. In the second Si site, Si is bonded in a 9-coordinate geometry to three equivalent Th and six Re atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(Al5Fe)2 by Materials Project

ThFe2Al10 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Th is bonded in a 10-coordinate geometry to four equivalent Fe and sixteen Al atoms. All Th–Fe bond lengths are 3.43 Å. There are a spread of Th–Al bond distances ranging from 3.15–3.64 Å. Fe is bonded in a 10-coordinate geometry to two equivalent Th and ten Al atoms. There are a spread of Fe–Al bond distances ranging from 2.54–2.73 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to one Th, two equivalent Fe, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.63–3.01 Å. In the second Al site, Al is bonded in a 2-coordinate geometry to two equivalent Th, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.69–2.81 Å. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Th, two equivalent Fe, and eight Al atoms. All Al–Al bond lengths are 2.78 Å. In the fourth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Th, two equivalent Fe, and eight Al atoms. There are one shorter (2.58 Å) and one longer (2.73 Å) Al–Al bond lengths. In the fifth Al site, Al is bonded in a 2-coordinate geometry to one Th, two equivalent Fe, and eight Al atoms. The Al–Al bond length is 2.68 Å.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Phosphate (U-Th)/He Thermochronology of Apollo 14 Melt Breccia 14311

Our ability to confidently characterize the impact history of the inner solar system is limited by discrepancies in radiometric dates and age interpretations for lunar rocks, impact melts, and recovered meteorites. It is therefore important to explore different thermally sensitive radiometric systems to unravel the timing and extent of the long term impact flux. Low-temperature thermochronology of lunar samples has the potential to provide more complementary geochronological datasets and further test dynamical models related to the evolution of the inner solar system (e.g., [1]). (U-Th)/He dating is based on the production of 4He atoms by radioactive alpha decay of U and Th (and to a lesser extent, Sm) in a crystal and the thermally activated volumetric diffusion of those 4He nuclides. At high temperatures, the crystal is an open system from which 4He can escape; at lower temperatures, 4He may be retained. This retention temperature depends on factors such as crystal structure and volume fraction of radiation damage in the crystal (e.g., [2, 3]), but is significantly lower for phosphate minerals compared to the diffusion of the radiogenic daughter products in other widely used chronometric systems (e.g., ~75°C in terrestrial apatite (U-Th)/He vs. ~500°C in apatite U-Th-Pb vs. ~900°C in zircon U-Th-Pb chronometry). Phosphate (U-Th)/He dating has been used to decipher peak temperatures and cooling rates related to terrestrial impact events (e.g., [4]). Pairing a low-temperature thermochronometer with higher-temperature approaches (i.e., a combined 207Pb-206Pb and (U-Th)/He approach), can therefore resolve multiple impact ages within a given sample or even grain. However, despite its potential, phosphate (U-Th)/He dating has not been reported on any lunar samples. Here we present the first lunar phosphate (U-Th)/He thermochronology on an Apollo 14 impact melt-breccia.

C A Diaz↗
DOE OSTI2020

Materials Data on Th(GeRu)2 by Materials Project

Th(RuGe)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight Ru and eight Ge atoms. There are a spread of Th–Ru bond distances ranging from 3.29–3.31 Å. There are a spread of Th–Ge bond distances ranging from 3.29–3.34 Å. There are two inequivalent Ru sites. In the first Ru site, Ru is bonded in a 4-coordinate geometry to four equivalent Th and four Ge atoms. There are two shorter (2.46 Å) and two longer (2.47 Å) Ru–Ge bond lengths. In the second Ru site, Ru is bonded in a 4-coordinate geometry to four equivalent Th and four Ge atoms. There are three shorter (2.46 Å) and one longer (2.47 Å) Ru–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Th, four Ru, and one Ge atom. The Ge–Ge bond length is 2.61 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Th, four Ru, and one Ge atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(CuSn)2 by Materials Project

Th(CuSn)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight Cu and eight Sn atoms. There are four shorter (3.37 Å) and four longer (3.43 Å) Th–Cu bond lengths. There are four shorter (3.37 Å) and four longer (3.55 Å) Th–Sn bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to four equivalent Th and four equivalent Sn atoms. All Cu–Sn bond lengths are 2.61 Å. In the second Cu site, Cu is bonded in a 9-coordinate geometry to four equivalent Th and five Sn atoms. There are one shorter (2.50 Å) and four longer (2.65 Å) Cu–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Th and five Cu atoms. In the second Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(NiSn)2 by Materials Project

Th(NiSn)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight Ni and eight Sn atoms. There are four shorter (3.25 Å) and four longer (3.44 Å) Th–Ni bond lengths. There are four shorter (3.33 Å) and four longer (3.49 Å) Th–Sn bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 8-coordinate geometry to four equivalent Th and four equivalent Sn atoms. All Ni–Sn bond lengths are 2.56 Å. In the second Ni site, Ni is bonded in a 9-coordinate geometry to four equivalent Th and five Sn atoms. There are one shorter (2.49 Å) and four longer (2.57 Å) Ni–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Th and five Ni atoms. In the second Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(GePt)2 by Materials Project

Th(PtGe)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight Pt and eight Ge atoms. There are four shorter (3.32 Å) and four longer (3.36 Å) Th–Pt bond lengths. There are four shorter (3.29 Å) and four longer (3.39 Å) Th–Ge bond lengths. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Pt–Ge bond lengths are 2.58 Å. In the second Pt site, Pt is bonded in a 9-coordinate geometry to four equivalent Th and five Ge atoms. There are one shorter (2.46 Å) and four longer (2.53 Å) Pt–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Pt atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Th and five Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(GeIr)2 by Materials Project

Th(IrGe)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight Ir and eight Ge atoms. There are four shorter (3.26 Å) and four longer (3.35 Å) Th–Ir bond lengths. There are four shorter (3.26 Å) and four longer (3.30 Å) Th–Ge bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ge atoms. All Ir–Ge bond lengths are 2.53 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Th and five Ge atoms. There are one shorter (2.44 Å) and four longer (2.51 Å) Ir–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Th and four equivalent Ir atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Th and five Ir atoms.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

NASA’s Moon to Mars (M2M) Transit Habitat (TH) Refinement Point of Departure (PoD) Design

As NASA prepares for the next human footsteps on the lunar surface, the Agency is already looking ahead to systems that will enable a sustained human presence on the lunar surface and mission to Mars, including a lunar Surface Habitat and Mars Transit Habitat (TH). This paper describes the latest NASA government reference design for the TH and how it will support NASA's Moon to Mars human exploration architecture. First, it will serve as a test and demonstration platform in lunar orbit, demonstrating capabilities required for long-duration microgravity human spaceflight as part of the lunar-Mars analog missions. Then, the TH will also serve as a major Mars habitation exploration element to support the crew during their transit from the lunar orbit to Mars and returning them safely to lunar orbit. This paper will cover several considerations contributing to the latest habitat design refinement, including data on the TH's concept of operations, system functional definition, subsystem assumptions, notional interior layouts, a detailed mass and volume breakdown, and trade studies and analyses required to close identified technology/ development/architecture gaps. In addition to a technical description of the TH, this paper describes how the current TH government reference design will achieve many of the current lunar and Mars mission goals. Additionally, there are many assumed technological advances needed to support the prescribed mission phases leading up to the crewed mission to Mars in the late 2030s. The paper will describe many of the TH systems requiring further technology development and identify architectural solutions to achieve these mass, reliability, autonomy, and crew health targets. As a whole, the data in the paper shows that a TH meeting the 43 metric tons launch mass/trans-Mars injection burn limits specified by the Evolvable Mars Campaign is achievable near the desired timeframe with moderate strategic investments including maintainable life support systems, re-purposable structures and packaging, and lightweight exercise modalities. It also identifies operational and technological options to reduce this mass to less than 41 metric tons, including staging of launch structure/packaging and alternate structural materials. The resulting design detail and data contained in this paper are intended to help teams across NASA and potential commercial, academic, or international partners understand the current performance targets of the Transit Habitat and vehicle interface considerations imposed by the latest Moon to Mars mission scope.

Habitation Systems↗
DOE OSTI2020

Materials Data on Th(PRu)2 by Materials Project

ThRu2P2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Th is bonded in a 1-coordinate geometry to five Ru and eight P atoms. There are a spread of Th–Ru bond distances ranging from 3.11–3.26 Å. There are a spread of Th–P bond distances ranging from 2.89–3.43 Å. There are two inequivalent Ru sites. In the first Ru site, Ru is bonded in a 12-coordinate geometry to two equivalent Th and four P atoms. There are a spread of Ru–P bond distances ranging from 2.24–2.46 Å. In the second Ru site, Ru is bonded in a 12-coordinate geometry to three equivalent Th and five P atoms. There are a spread of Ru–P bond distances ranging from 2.36–2.58 Å. There are two inequivalent P sites. In the first P site, P is bonded in a 10-coordinate geometry to four equivalent Th, four Ru, and two equivalent P atoms. Both P–P bond lengths are 2.61 Å. In the second P site, P is bonded in a 9-coordinate geometry to four equivalent Th and five Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(Al2Fe)4 by Materials Project

Th(FeAl2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight equivalent Fe and twelve Al atoms. All Th–Fe bond lengths are 3.36 Å. There are four shorter (3.04 Å) and eight longer (3.20 Å) Th–Al bond lengths. Fe is bonded in a 12-coordinate geometry to two equivalent Th, two equivalent Fe, and eight Al atoms. Both Fe–Fe bond lengths are 2.52 Å. There are four shorter (2.55 Å) and four longer (2.67 Å) Fe–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent Th, four equivalent Fe, and six Al atoms. There are a spread of Al–Al bond distances ranging from 2.74–2.79 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to one Th, four equivalent Fe, and five Al atoms. The Al–Al bond length is 2.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(AlAu)2 by Materials Project

ThAu2Al2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight Au and eight Al atoms. There are four shorter (3.37 Å) and four longer (3.41 Å) Th–Au bond lengths. There are four shorter (3.36 Å) and four longer (3.44 Å) Th–Al bond lengths. There are two inequivalent Au sites. In the first Au site, Au is bonded to four equivalent Th and four equivalent Al atoms to form distorted AuTh4Al4 tetrahedra that share corners with twelve equivalent AlTh4Au4 tetrahedra, edges with two equivalent AlTh4Au4 tetrahedra, edges with four equivalent AuTh4Al4 tetrahedra, and faces with four equivalent AuTh4Al4 tetrahedra. All Au–Al bond lengths are 2.60 Å. In the second Au site, Au is bonded in a 5-coordinate geometry to four equivalent Th and five Al atoms. There are one shorter (2.51 Å) and four longer (2.59 Å) Au–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to four equivalent Th and four equivalent Au atoms to form AlTh4Au4 tetrahedra that share corners with twelve equivalent AuTh4Al4 tetrahedra, edges with two equivalent AuTh4Al4 tetrahedra, edges with four equivalent AlTh4Au4 tetrahedra, and faces with four equivalent AlTh4Au4 tetrahedra. In the second Al site, Al is bonded in a 5-coordinate geometry to four equivalent Th and five Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(SiIr)2 by Materials Project

Th(IrSi)2 crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight Ir and eight equivalent Si atoms. There are four shorter (3.27 Å) and four longer (3.29 Å) Th–Ir bond lengths. There are four shorter (3.27 Å) and four longer (3.29 Å) Th–Si bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Th and four equivalent Si atoms. All Ir–Si bond lengths are 2.43 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Th and four equivalent Si atoms. All Ir–Si bond lengths are 2.42 Å. Si is bonded in a 4-coordinate geometry to four equivalent Th and four Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The impact of feedstock size and composition on the hydrothermal growth of (U,Th)O 2

Bulk crystal growth of refractory oxides requires unique approaches, and the U x Th 1-x O 2 solid solution is no exception. Hydrothermal transport reactions of U 0.1 Th 0.9 O 2 onto ThO 2 seeds with feedstocks comprised of U 0.1 Th 0.9 O 2 or mixtures of UO 2 and ThO 2 with a nominal composition of U 0.1 Th 0.9 O 2 are investigated with µ-Raman spectroscopy and X-ray fluorescence. In each case, the trends in stoichiometry as a function of distance from the seed are analyzed and the deviations from the nominal stoichiometry discussed. When the feedstock is composed of mixed oxides, the particle surface area’s influence on the feedstock dissolution rate is the dominant factor and can produce U-rich stoichiometries as high as U 0.75 Th 0.25 O 2 . When composed solely of U 0.1 Th 0.9 O 2 , the total growth amount depends on the particle size, but the obtained stoichiometry is the product of differing solubilities. Although the U0.1Th0.9O 2 feedstock produces the most homogeneous growth, the ending growth of the smallest particle UO 2 /ThO 2 mixture yields the stoichiometry closest to U 0.1 Th 0.9 O 2 . How to obtain desired stoichiometries from mixtures by matching the particle size and solubilities is briefly discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Sequential Bond Dissociation Energies of Th + (CO) x , x = 3–6: Guided Ion Beam Collision-Induced Dissociation and Quantum Computational Studies

Collision-induced dissociation (CID) of [Th,xC,xO] + , x = 3–6, with Xe is performed using a guided ion beam tandem mass spectrometer (GIBMS). Products are formed exclusively by the loss of CO ligands. Analyses of the kinetic energy-dependent CID product cross sections yield bond dissociation energies (BDEs) of (CO) x–1 Th + –CO at 0 K as 1.09 ± 0.05, 0.82 ± 0.07, 0.63 ± 0.05, and 0.70 ± 0.05 eV, respectively. Different structures of [Th,xC,xO] + were explored using various electronic structure methods, and BDEs for CO ligand loss from precursor [Th,xC,xO] + complexes were computed. Both experimental and theoretical results corroborate that the structures of [Th,xC,xO] + , x = 3–6, formed experimentally are homoleptic thorium cation carbonyl complexes, Th + (CO) x . The nonmonotonic trend in experimental BDEs is reproduced theoretically, although ambiguities in the spin states of the x = 4–6 complexes (doublet or quartet) remain. BDEs calculated at the coupled cluster with single, double, and perturbative triple excitations (CCSD(T))/cc-pVXZ//B3LYP/cc-PVXZ (X = T and Q) level and a complete basis set (CBS) extrapolation agree reasonably well with the experimental values for all complexes. Thorium oxide ketenylidene carbonyl cations, OTh + CCO(CO) y , y = 1–4, were calculated to be the most stable structures of [Th,xC,xO] + , x = 3–6, respectively; however, these are not observed in our experiment. Potential energy profiles (PEPs) having either quartet or doublet spin calculated at the B3LYP/cc-pVQZ level suggest that the failure to observe OTh + CCO(CO) y , y = 1–4, is the result of a barrier corresponding to the C–C bond formation, making the formation of OTh + CCO(CO) y inaccessible kinetically under the present experimental conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Enrichment of the Galactic disc with neutron-capture elements: Gd, Dy, and Th

The study of the origin of heavy elements is one of the main goals of nuclear astrophysics. In this paper, we present new observational data for the heavy r-process elements gadolinium (Gd, Z= 64), dysprosium (Dy, Z= 66), and thorium (Th, Z= 90) in a sample of 276 Galactic disc stars (–1.0 < [Fe/H] < + 0.3). The stellar spectra have a high resolution of 42 000 and 75 000, and the signal-to-noise ratio higher than 100. The LTE abundances of Gd, Dy, and Th have been determined by comparing the observed and synthetic spectra for three Gd lines (149 stars), four Dy lines (152 stars), and the Th line at 4019.13 Å (170 stars). For about 70 percent of the stars in our sample, Gd and Dy are measured for the first time, and Th for 95 percent of the stars. Typical errors vary from 0.07 to 0.16 dex. This paper provides the first extended set of Th observations in the Milky Way disc. Here together with europium (Eu, Z= 63) data from our previous studies, we have compared these new observations with nucleosynthesis predictions and Galactic Chemical Evolution simulations. We confirm that [Gd/Fe] and [Dy/Fe] show the same behaviour of Eu. We study with GCE simulations the evolution of [Th/Fe] in comparison with [Eu/Fe], showing that unlike Eu, either the Th production is metallicity dependent in case of a unique source of the r-process in the Galaxy, or the frequency of the Th-rich r-process source is decreasing with the increase in [Fe/H].

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Laser Excitation of the Th-229 Nucleus

The 8.4 eV nuclear isomer state in Th-229 is resonantly excited in Th-doped CaF 2 crystals using a tabletop tunable laser system. A resonance fluorescence signal is observed in two crystals with different Th-229 dopant concentrations, while it is absent in a control experiment using Th-232. The nuclear resonance for the Th 4 + ions in Th: CaF 2 is measured at the wavelength 148.3821(5) nm, frequency 2020.409(7) THz, and the fluorescence lifetime in the crystal is 630(15) s, corresponding to an isomer half-life of 1740(50) s for a nucleus isolated in vacuum. These results pave the way toward Th-229 nuclear laser spectroscopy and realizing optical nuclear clocks. Published by the American Physical Society 2024

Physics↗
DOE OSTI2020

Materials Data on Th(GeAu)2 by Materials Project

Th(AuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 8-coordinate geometry to eight equivalent Au and eight equivalent Ge atoms. All Th–Au bond lengths are 3.46 Å. All Th–Ge bond lengths are 3.37 Å. Au is bonded to four equivalent Th and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing AuTh4Ge4 tetrahedra. All Au–Ge bond lengths are 2.64 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Th, four equivalent Au, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗