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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A simulated annealing approach to schedule optimization for the SES facility

The Shuttle Engineering Simulator (SES) is a facility which houses the software and hardware for a variety of simulation systems. The simulators include the Autonomous Remote Manipulator, the Manned Maneuvering Unit, Orbiter/Space Station docking, and shuttle entry and landing. The SES simulators are used by various groups throughout NASA. For example, astronauts use the SES to practice maneuvers with the shuttle equipment; programmers use the SES to test flight software; and engineers use the SES for design and analysis studies. Due to its high demand, the SES is busy twenty-four hours a day and seven days a week. Scheduling the facility is a problem that is constantly growing and changing with the addition of new equipment. Currently a number of small independent programs have been developed to help solve the problem, but the long-term answer lies in finding a flexible, integrated system that provides the user with the ability to create, optimize, and edit the schedule. COMPASS is an interactive and highly flexible scheduling system. However, until recently COMPASS did not provide any optimization features. This paper describes the simulated annealing extension to COMPASS. It now allows the user to interweave schedule creation, revision, and optimization. This practical approach was necessary in order to satisfy the operational requirements of the SES.

Mcmahon, Mary Beth↗
DOE OSTI2020

Materials Data on TaTl3(SeS)2 by Materials Project

TaTl3(SeS)2 crystallizes in the orthorhombic Fmm2 space group. The structure is three-dimensional and consists of two TaTl3(SeS)2 frameworks. Ta5+ is bonded in a tetrahedral geometry to two equivalent Se2- and two equivalent S2- atoms. Both Ta–Se bond lengths are 2.44 Å. Both Ta–S bond lengths are 2.28 Å. There are two inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a 12-coordinate geometry to two equivalent Se2- and two equivalent S2- atoms. Both Tl–Se bond lengths are 3.26 Å. Both Tl–S bond lengths are 3.25 Å. In the second Tl1+ site, Tl1+ is bonded in a 12-coordinate geometry to two equivalent Se2- and two equivalent S2- atoms. Both Tl–Se bond lengths are 3.28 Å. Both Tl–S bond lengths are 3.23 Å. Se2- is bonded in a 1-coordinate geometry to one Ta5+ and three Tl1+ atoms. S2- is bonded in a distorted single-bond geometry to one Ta5+ and three Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

On the bulk compaction of brittle granular materials, part I: SeS analysis of axial compression to 4000 MPa

The bulk compaction of granular materials has been studied for decades to interpret and manage responses for soils and powder-based component fabrication, and geophysical, celestial, and ballistic impact. Their bulk or macroscopic compaction response is limited by what occurs at the granular or microstructural scale. Motivation existed to more closely examine that association specific to granular brittle materials (e.g., ceramics and glasses). That examination is offered in a series of three companion papers where Part I describes a new supplemental analysis adopted to bulk compaction response involving relatively high compaction stresses (4000 MPa). Bulk compactions of vitreous silicates and crystalline quartzes were interpreted in three ways, including that of a new analysis that considers the product of void ratio (e) and stress (S) as a function of S, hereafter referred to as “SeS analysis”. In conclusion, the SeS analysis was found to be an informative supplement to conventional bulk compaction analyses because it provides more consistent higher sensitivity for the identification of bulk density rate increase with increasing compaction (softening); a rate increase that arises from the cumulative effect of the onsets and progression of compaction-induced yielding, fracture or comminution, densification, phase change, or combinations thereof occurring at the granular or microstructural scale.

compaction↗
DOE OSTI2023

AmeriFlux FLUXNET-1F US-Ses Sevilleta shrubland

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-Ses Sevilleta shrubland. This is the FLUXNET version of the carbon flux data for the site US-Ses Sevilleta shrubland produced by applying the standard ONEFlux (1F) software. Site Description - The Sevilleta Desert Shrubland site is located in Larrea-dominated shrubland in the northern Chihuahuan Desert of the Rio Grande Valley, on the Sevilleta National Wildlife Refuge (SNWR). The site is within the McKenzie Flats area of the Sevilleta National Wildlife Refuge (NWR). McKenzie Flats is an extensive (~130 km2), nearly flat, mixed-species desert grassland bounded on the east by Los Pinos Mountains and on the west by the Rio Grande. Historically, this area has been used for livestock grazing; however, the McKenzie Flats have not been grazed since 1973 and the effects of this previous grazing are considered negligible for the purposes of this study. The density of Larrea at this site is 0.9 m-2 , interspersed with C4 perennial grasses (Bouteloua gracilis, B. eriopoda, Sporobolis spp., Hilaria jamesii, Muhlenbergia spp.). Sixty percent of mean annual precipitation comes in isolated, short duration showers during the monsoon season (July – September); the remainder arrives with winter frontal systems, although with considerable year-to-year variation.

Litvak, Marcy↗
DOE OSTI2020

Improved Performance of Cu(InGa)(SeS) 2 PV Modules Using the Reaction of Metal Precursors. Final Report

This project “Improved Performance of Cu(InGa)(SeS) 2 PV Modules using the Reaction of Metal Precursors” was a partnership led by the Institute of Energy Conversion (IEC) at the University of Delaware with Columbia University and the Molecular Foundry at the Lawrence Berkeley National Laboratory. The aim was to develop pathways to improve Cu(InGa)(SeS) 2 (CIGSS) thin film photovoltaic modules using processes compatible with low manufacturing cost. The CIGSS approach investigated was a two-step process including deposition of metal precursor films following by reaction in hydride gases utilizing IEC’s novel reactor. The process was similar to that under commercial development by the project’s industry partner Stion. When Stion went out of business mid-project the focus changed to a rapid thermal process considered more commercially viable. Approaches to improve the performance of solar cells using the reacted films focused on two material innovations. First, the overall Ga content was increased to increase the operating voltage, which is desirable for scale-up to commercial modules. Second, the processing and performance advantages arising from Ag alloying were investigated. Advanced characterization guided process and material development including control of relative composition gradients. Research on the formation of Cu-Ga-In metal precursors utilized sputtering deposition which is normally used in commercial applications. The work resulted in processes for deposition of precursor stacks with increased relative Ga content and effects of deposition parameters on morphology and phase composition were established. It was shown that the metal precursor films have comparable phase composition and morphology so subsequent reaction follows from the same starting point. The addition of Ag to the metal precursors gave more uniform morphology and improved adhesion of reacted films which enable higher reaction temperature for faster processing. A novel outcome was the discovery of a previously undocumented material phase in sputter-deposited and evaporated Ag-Cu-In-Ga thin films. Hydride gas reaction processes including time-temperature-concentration profiles were developed for different precursor compositions. This enables control of composition profiles to engineer through-film gradients for solar cell optimization with characterization and simulations used to correlate measured film composition profiles to measurements of devices. In particular, the gradient of sulfur at the front of the CIGSS film was found to be critical. The simulations guided process development leading to improved reproducibility of devices improved performance with higher Ga content and higher voltage. With Ag-alloyed precursors, the reaction pathways leading were determined. A significant finding was that Ag-alloying increases the reaction rate to completely convert precursor films to the final chalcopyrite which could enable reduced reaction time to benefit manufacturability. To maintain potential commercial viability, the process under investigation was refocused to a rapid thermal process that could potentially be incorporated into an in-line process for manufacturing. Precursors with different composition were capped with an extra selenium layer and reacted in hydrogen sulfide 5-15 minutes, compared to typically 2 hours in the previous multi-step batch process. Critical RTP parameters were identified to control the reaction. Further optimization would be needed for high efficiency solar cells but pathways to high quality devices with further optimization and improved heating uniformity were developed. The project also developed new optoelectronic characterization approaches with a focus on development and application of spatial- and time-resolved photoluminescence and a custom mapping photoluminescence microscope built. It was shown how critical electronic transport properties strongly depend on the chemical composition of the material and that a wide range of samples show inhomogeneity on a length scale larger than the grains in the films. Additionally, two-photon excitation capability was developed to distinguish bulk vs surface losses. The project advances the state-of-the -art for precursor reaction processes in several ways that could impact manufacturing. This includes validation of approaches to increase voltage and establishment of model-guided control to form optimal composition profiles. The application of process control approaches with knowledge of phase formation and reaction pathways can be critically valuable in designing a large-scale process.

14 SOLAR ENERGY↗
NASA NTRS2008

SES and Acoustics at GSFC

This paper presents air and surface cleanliness characterization of the acoustics test facility and large (SES) thermal vacuum chamber at Goddard Space flight Center in Greenbelt, MD during the New Horizons Pluto probe program. It is shown that slow back-fill of the SES chamber is necessary to prevent excessive particle redistribution.

Hogue, Patrick↗
NASA NTRS2010

Enhancements to the NASA/Goddard Space Flight Center (GSFC) Space Environment Simulator (SES) Facility to Support Cryogenic Testing of the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM)

NASA is the mission lead for the James Webb Space Telescope (JWST), the next of the "Great Observatories", scheduled for launch in 2014. It is directly responsible for the integration and test of the Integrated Science Instrument Module (ISIM), which includes a composite truss structure provided by NASA, and four science instruments sponsored and provided by NASA, the European Space Agency (ESA), the Canadian Space Agency (CSA), and the European Consortium (EC). Three of the four instruments are passively cooled and designed to operate at temperatures in the 36K to 40K range, and the fourth instrument is actively cooled to approximately 6K. The ISIM will undergo several performance tests at various levels of integration in the NASA Goddard Space Flight Center's (GSFC) Space Environment Simulator (SES), GSFC's largest thermal vacuum chamber. These activities range from Cryo-cycling the bare flight composite structure to thermal balance and performance testing of the full ISIM module. This paper describes the enhancements made to the SES chamber in order to support all cryogenic thermal vacuum testing of the ISIM. Upgrades discussed include: design and fabrication of a very large, removable and reconfigurable helium shroud; a new valve box permitting independent flow control of gaseous helium (GHe) to up to ten zones; and development of in-situ 3-dimensional photogrammetry capability in a cryogenic environment. Also presented will be select results from several facility tests already conducted to verify the chamber capabilities and optimize operational procedures, including the Helium Shroud -03 Configuration Acceptance Test, and the Helium Shroud -01 Configuration Chamber Certification Test.

Cleveland, Paul↗
DOE OSTI2020

Materials Data on SeS by Materials Project

SeS is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Se2- is bonded to six equivalent S2+ atoms to form a mixture of corner and edge-sharing SeS6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Se–S bond lengths are 2.71 Å. S2+ is bonded to six equivalent Se2- atoms to form a mixture of corner and edge-sharing SSe6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZnCu2Ge(SeS)2 by Materials Project

Cu2ZnGe(SeS)2 is Clathrate-derived structured and crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. Cu1+ is bonded to two equivalent Se2- and two S2- atoms to form CuSe2S2 tetrahedra that share corners with four equivalent CuSe2S2 tetrahedra, corners with four equivalent ZnSe2S2 tetrahedra, and corners with four equivalent GeSe2S2 tetrahedra. There are one shorter (2.43 Å) and one longer (2.46 Å) Cu–Se bond lengths. Both Cu–S bond lengths are 2.30 Å. Zn2+ is bonded to two equivalent Se2- and two S2- atoms to form ZnSe2S2 tetrahedra that share corners with four equivalent GeSe2S2 tetrahedra and corners with eight equivalent CuSe2S2 tetrahedra. Both Zn–Se bond lengths are 2.50 Å. There are one shorter (2.34 Å) and one longer (2.39 Å) Zn–S bond lengths. Ge4+ is bonded to two equivalent Se2- and two S2- atoms to form GeSe2S2 tetrahedra that share corners with four equivalent ZnSe2S2 tetrahedra and corners with eight equivalent CuSe2S2 tetrahedra. Both Ge–Se bond lengths are 2.42 Å. There are one shorter (2.27 Å) and one longer (2.31 Å) Ge–S bond lengths. Se2- is bonded to two equivalent Cu1+, one Zn2+, and one Ge4+ atom to form SeZnCu2Ge tetrahedra that share corners with four equivalent SeZnCu2Ge tetrahedra and corners with eight SZnCu2Ge tetrahedra. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Cu1+, one Zn2+, and one Ge4+ atom to form SZnCu2Ge tetrahedra that share corners with four equivalent SZnCu2Ge tetrahedra and corners with eight equivalent SeZnCu2Ge tetrahedra. In the second S2- site, S2- is bonded to two equivalent Cu1+, one Zn2+, and one Ge4+ atom to form SZnCu2Ge tetrahedra that share corners with four equivalent SZnCu2Ge tetrahedra and corners with eight equivalent SeZnCu2Ge tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr4FeCu(SeS)4 by Materials Project

Cr4FeCu(SeS)4 is Spinel-derived structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Cr3+ is bonded to three equivalent Se2- and three equivalent S2- atoms to form CrSe3S3 octahedra that share corners with three equivalent FeSe4 tetrahedra, corners with three equivalent CuS4 tetrahedra, and edges with six equivalent CrSe3S3 octahedra. All Cr–Se bond lengths are 2.57 Å. All Cr–S bond lengths are 2.39 Å. Fe3+ is bonded to four equivalent Se2- atoms to form FeSe4 tetrahedra that share corners with twelve equivalent CrSe3S3 octahedra. The corner-sharing octahedral tilt angles are 60°. All Fe–Se bond lengths are 2.36 Å. Cu1+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with twelve equivalent CrSe3S3 octahedra. The corner-sharing octahedral tilt angles are 55°. All Cu–S bond lengths are 2.36 Å. Se2- is bonded to three equivalent Cr3+ and one Fe3+ atom to form a mixture of distorted corner and edge-sharing SeCr3Fe tetrahedra. S2- is bonded in a distorted rectangular see-saw-like geometry to three equivalent Cr3+ and one Cu1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbCu3(SeS)2 by Materials Project

NbCu3(SeS)2 is Stannite-like structured and crystallizes in the orthorhombic Cmm2 space group. The structure is three-dimensional. Nb5+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form NbSe2S2 tetrahedra that share edges with six CuSe2S2 tetrahedra. Both Nb–Se bond lengths are 2.46 Å. Both Nb–S bond lengths are 2.34 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form CuSe2S2 tetrahedra that share corners with eight CuSe2S2 tetrahedra and edges with two equivalent NbSe2S2 tetrahedra. Both Cu–Se bond lengths are 2.51 Å. Both Cu–S bond lengths are 2.34 Å. In the second Cu1+ site, Cu1+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form CuSe2S2 tetrahedra that share corners with eight equivalent CuSe2S2 tetrahedra and edges with two equivalent NbSe2S2 tetrahedra. Both Cu–Se bond lengths are 2.48 Å. Both Cu–S bond lengths are 2.36 Å. Se2- is bonded to one Nb5+ and three Cu1+ atoms to form distorted SeNbCu3 tetrahedra that share corners with two equivalent SeNbCu3 tetrahedra, corners with four equivalent SNbCu3 tetrahedra, an edgeedge with one SeNbCu3 tetrahedra, and edges with two equivalent SNbCu3 tetrahedra. S2- is bonded to one Nb5+ and three Cu1+ atoms to form distorted SNbCu3 tetrahedra that share corners with two equivalent SNbCu3 tetrahedra, corners with four equivalent SeNbCu3 tetrahedra, an edgeedge with one SNbCu3 tetrahedra, and edges with two equivalent SeNbCu3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VCu3(SeS)2 by Materials Project

VCu3(SeS)2 is Stannite-like structured and crystallizes in the orthorhombic Cmm2 space group. The structure is three-dimensional. V5+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form VSe2S2 tetrahedra that share edges with six CuSe2S2 tetrahedra. Both V–Se bond lengths are 2.35 Å. Both V–S bond lengths are 2.22 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form CuSe2S2 tetrahedra that share corners with eight CuSe2S2 tetrahedra and edges with two equivalent VSe2S2 tetrahedra. Both Cu–Se bond lengths are 2.43 Å. Both Cu–S bond lengths are 2.28 Å. In the second Cu1+ site, Cu1+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form CuSe2S2 tetrahedra that share corners with eight equivalent CuSe2S2 tetrahedra and edges with two equivalent VSe2S2 tetrahedra. Both Cu–Se bond lengths are 2.41 Å. Both Cu–S bond lengths are 2.30 Å. Se2- is bonded to one V5+ and three Cu1+ atoms to form distorted SeVCu3 tetrahedra that share corners with two equivalent SeVCu3 tetrahedra, corners with four equivalent SVCu3 tetrahedra, an edgeedge with one SeVCu3 tetrahedra, and edges with two equivalent SVCu3 tetrahedra. S2- is bonded to one V5+ and three Cu1+ atoms to form distorted SVCu3 tetrahedra that share corners with two equivalent SVCu3 tetrahedra, corners with four equivalent SeVCu3 tetrahedra, an edgeedge with one SVCu3 tetrahedra, and edges with two equivalent SeVCu3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr4(SeS)3 by Materials Project

Cr4(SeS)3 is Ilmenite-like structured and crystallizes in the trigonal R3 space group. The structure is three-dimensional. there are four inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to three equivalent Se2- and three equivalent S2- atoms to form a mixture of corner and edge-sharing CrSe3S3 octahedra. The corner-sharing octahedra tilt angles range from 46–48°. All Cr–Se bond lengths are 2.52 Å. All Cr–S bond lengths are 2.41 Å. In the second Cr3+ site, Cr3+ is bonded to three equivalent Se2- and three equivalent S2- atoms to form a mixture of corner and face-sharing CrSe3S3 octahedra. The corner-sharing octahedra tilt angles range from 46–50°. All Cr–Se bond lengths are 2.56 Å. All Cr–S bond lengths are 2.36 Å. In the third Cr3+ site, Cr3+ is bonded to three equivalent Se2- and three equivalent S2- atoms to form a mixture of corner, edge, and face-sharing CrSe3S3 octahedra. The corner-sharing octahedral tilt angles are 50°. All Cr–Se bond lengths are 2.54 Å. All Cr–S bond lengths are 2.42 Å. In the fourth Cr3+ site, Cr3+ is bonded to three equivalent Se2- and three equivalent S2- atoms to form a mixture of corner, edge, and face-sharing CrSe3S3 octahedra. The corner-sharing octahedral tilt angles are 48°. All Cr–Se bond lengths are 2.52 Å. All Cr–S bond lengths are 2.35 Å. Se2- is bonded in a rectangular see-saw-like geometry to four Cr3+ atoms. S2- is bonded in a distorted rectangular see-saw-like geometry to four Cr3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr2Cu(SeS)2 by Materials Project

Cr2Cu(SeS)2 is Spinel-derived structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Cr3+ is bonded to three equivalent Se2- and three equivalent S2- atoms to form CrSe3S3 octahedra that share corners with six CuS4 tetrahedra and edges with six equivalent CrSe3S3 octahedra. All Cr–Se bond lengths are 2.53 Å. All Cr–S bond lengths are 2.39 Å. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with twelve equivalent CrSe3S3 octahedra. The corner-sharing octahedral tilt angles are 55°. All Cu–S bond lengths are 2.33 Å. In the second Cu2+ site, Cu2+ is bonded to four equivalent Se2- atoms to form CuSe4 tetrahedra that share corners with twelve equivalent CrSe3S3 octahedra. The corner-sharing octahedral tilt angles are 60°. All Cu–Se bond lengths are 2.35 Å. Se2- is bonded to three equivalent Cr3+ and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCr3Cu tetrahedra. S2- is bonded in a rectangular see-saw-like geometry to three equivalent Cr3+ and one Cu2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCu3(SeS)2 by Materials Project

TaCu3(SeS)2 is Stannite-like structured and crystallizes in the orthorhombic Cmm2 space group. The structure is three-dimensional. Ta5+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form TaSe2S2 tetrahedra that share edges with six CuSe2S2 tetrahedra. Both Ta–Se bond lengths are 2.46 Å. Both Ta–S bond lengths are 2.33 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form CuSe2S2 tetrahedra that share corners with eight CuSe2S2 tetrahedra and edges with two equivalent TaSe2S2 tetrahedra. Both Cu–Se bond lengths are 2.50 Å. Both Cu–S bond lengths are 2.35 Å. In the second Cu1+ site, Cu1+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form CuSe2S2 tetrahedra that share corners with eight equivalent CuSe2S2 tetrahedra and edges with two equivalent TaSe2S2 tetrahedra. Both Cu–Se bond lengths are 2.47 Å. Both Cu–S bond lengths are 2.37 Å. Se2- is bonded to one Ta5+ and three Cu1+ atoms to form distorted SeTaCu3 tetrahedra that share corners with two equivalent SeTaCu3 tetrahedra, corners with four equivalent STaCu3 tetrahedra, an edgeedge with one SeTaCu3 tetrahedra, and edges with two equivalent STaCu3 tetrahedra. S2- is bonded to one Ta5+ and three Cu1+ atoms to form distorted STaCu3 tetrahedra that share corners with two equivalent STaCu3 tetrahedra, corners with four equivalent SeTaCu3 tetrahedra, an edgeedge with one STaCu3 tetrahedra, and edges with two equivalent SeTaCu3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mo3(SeS)2 by Materials Project

Mo3(SeS)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Mo+2.67+ sites. In the first Mo+2.67+ site, Mo+2.67+ is bonded to three Se2- and two S2- atoms to form a mixture of corner and edge-sharing MoSe3S2 square pyramids. All Mo–Se bond lengths are 2.56 Å. There are one shorter (2.43 Å) and one longer (2.44 Å) Mo–S bond lengths. In the second Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form a mixture of corner and edge-sharing MoSe2S3 square pyramids. Both Mo–Se bond lengths are 2.57 Å. There are a spread of Mo–S bond distances ranging from 2.43–2.45 Å. In the third Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form a mixture of corner and edge-sharing MoSe2S3 square pyramids. There are one shorter (2.54 Å) and one longer (2.55 Å) Mo–Se bond lengths. There are one shorter (2.44 Å) and two longer (2.45 Å) Mo–S bond lengths. In the fourth Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form MoSe2S3 square pyramids that share corners with four MoSe2S3 square pyramids and edges with five MoSe3S2 square pyramids. There are one shorter (2.57 Å) and one longer (2.61 Å) Mo–Se bond lengths. There are two shorter (2.45 Å) and one longer (2.50 Å) Mo–S bond lengths. In the fifth Mo+2.67+ site, Mo+2.67+ is bonded to three Se2- and two S2- atoms to form a mixture of corner and edge-sharing MoSe3S2 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.61 Å. There are one shorter (2.42 Å) and one longer (2.50 Å) Mo–S bond lengths. In the sixth Mo+2.67+ site, Mo+2.67+ is bonded to two Se2- and three S2- atoms to form a mixture of corner and edge-sharing MoSe2S3 square pyramids. There are one shorter (2.56 Å) and one longer (2.57 Å) Mo–Se bond lengths. There are a spread of Mo–S bond distances ranging from 2.44–2.46 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to three Mo+2.67+ atoms. In the fourth Se2- site, Se2- is bonded in a 6-coordinate geometry to three Mo+2.67+ atoms. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the second S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the third S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms. In the fourth S2- site, S2- is bonded in a 4-coordinate geometry to four Mo+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electronic and structural properties of RbCe X 2 ( X 2 : O 2 , S 2 , SeS, Se 2 , TeSe, Te 2 )

We report triangular lattice delafossite compounds built from magnetic lanthanide ions are a topic of recent interest due to their frustrated magnetism and realization of quantum disordered magnetic ground states. Here we report the evolution of the structure and electronic ground states of RbCeX 2 compounds, built from a triangular lattice of Ce 3+ ions, upon varying their anion character (X 2 =O 2 , S 2 , SeS, Se 2 , TeSe, Te 2 ). This includes the discovery of a new member of this series, RbCeO 2 , that potentially realizes a quantum disordered ground state analogous to NaYbO 2 . Magnetization and susceptibility measurements reveal that all compounds manifest mean-field antiferromagnetic interactions and, with the exception of the oxide, possess signatures of magnetic correlations onset below 1 K. The crystalline electric field level scheme is explored via neutron scattering and ab initio calculations in order to model the intramultiplet splitting of the J=5/2 multiplet. In addition to the two excited doublets expected within the J=5/2 manifold, we observe one extra local mode present across the sample series. This added mode shifts downward in energy with increasing anion mass and decreasing crystal field strength, suggesting a long-lived anomalous mode endemic to anion motion about the Ce3 + sites.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1971

Variation in spectral irradiance of the SES solar simulator

A test to determine the spectral characteristics of the solar simulation produced by the solar environment simulator (SES) comprised a statistical analysis to determine the spectral variance, and its effect on the average absorptivity of surface coatings.

Mcnutt, A. E.↗