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All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Reducing software security risk through an integrated approach

The fourth quarter delivery, FY'01 for this RTOP is a Property-Based Testing (PBT), 'Tester's Assistant' (TA). The TA tool is to be used to check compiled and pre-compiled code for potential security weaknesses that could be exploited by hackers. The TA Instrumenter, implemented mostly in C++ (with a small part in Java), parsels two types of files: Java and TASPEC. Security properties to be checked are written in TASPEC. The Instrumenter is used in conjunction with the Tester's Assistant Specification (TASpec)execution monitor to verify the security properties of a given program.

software security↗
NASA NTRS2008

Oxidation of ZrB2 SiC TaSi2 Materials at Ultra High Temperatures

ZrB2 - 20v% SiC - 20v% TaSi2 was oxidized in stagnant air for ten minute cycles for times up to 100 minutes at 1627 C and 1927 C. The sample oxidized at 1627 C showed oxidation resistance better than that of the standard ZrB2 - 20v% SiC. The sample oxidized at 1927 C, however, showed evidence of liquid phase formation and complex oxidation products. The sample exposed at 1927 C was analyzed in detail by scanning electron microprobe and wavelength dispersive spectroscopy to understand the complex oxidation and melting reactions occurring during exposure. The as hot-pressed material shows the formation of a Zr(Ta)B2 phase in addition to the three phases in the nominal composition already noted. After oxidation, the TaSi2 in the matrix was completely reacted to form Ta(Zr)C. The layered oxidation products included SiO2, ZrO2, Ta2O5, and a complex oxide containing both Zr and Ta. Likely reactions are proposed based on thermodynamic phase stability and phase morphology.

Opila, E.↗
NASA NTRS2009

Effects of Tantalum on the Temporal Evolution of a Model Ni-Al-Cr Superalloy During Phase Decomposition

The effects of a 2.0 at.% addition of Ta to a model Ni-10.0Al-8.5Cr (at.%) superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The gamma'(Ll2)-precipitate morphology that develops as a result of gamma-(fcc)matrix phase decomposition is found to evolve from a bimodal distribution of spheroidal precipitates, to {001}-faceted cuboids and parallelepipeds aligned along the elastically soft {001}-type directions. The phase compositions and the widths of the gamma'-precipitate/gamma-matrix heterophase interfaces evolve temporally as the Ni-Al-Cr-Ta alloy undergoes quasi-stationary state coarsening after 1 h of aging. Tantalum is observed to partition preferentially to the gamma'-precipitate phase, and suppresses the mobility of Ni in the gamma-matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma'/gamma interface. Additionally, computational modeling, employing Thermo-Calc, Dictra and PrecipiCalc, is employed to elucidate the kinetic pathways that lead to phase decomposition in this concentrated Ni-Al-Cr-Ta alloy.

Booth, Morrison, Christopher↗
NASA NTRS2003

The Micro-Arcsecond Metrology Testbed

The Micro-Arcsecond Metrology (MAM) testbed is a ground-based system of optical and electronic equipment for testing components, systems, and engineering concepts for the Space Interferometer Mission (SIM) and similar future missions, in which optical interferometers will be operated in outer space. In addition, the MAM testbed is of interest in its own right as a highly precise metrological system. The designs of the SIM interferometer and the MAM testbed reflect a requirement to measure both the position of the starlight central fringe and the change in the internal optical path of the interferometer with sufficient spatial resolution to generate astrometric data with angular resolution at the microarcsecond level. The internal path is to be measured by use of a small metrological laser beam of 1,319-nm wavelength, whereas the position of the starlight fringe is to be estimated by use of a charge-coupled-device (CCD) image detector sampling a large concentric annular beam. For the SIM to succeed, the optical path length determined from the interferometer fringes must be tracked by the metrological subsystem to within tens of picometers, through all operational motions of an interferometer delay line and siderostats. The purpose of the experiments performed on the MAM testbed is to demonstrate this agreement in a large-scale simulation that includes a substantial portion of the system in the planned configuration for operation in outer space. A major challenge in this endeavor is to align the metrological beam with the starlight beam in order to maintain consistency between the metrological and starlight subsystems at the system level. The MAM testbed includes an optical interferometer with a white light source, all major optical components of a stellar interferometer, and heterodyne metrological sensors. The aforementioned subsystems are installed in a large vacuum chamber in order to suppress atmospheric and thermal disturbances. The MAM is divided into two distinct subsystems: the test article (TA), which is the interferometer proper, and the inverse interferometer pseudo-star (IIPS), which synthesizes the light coming from a distant target star by providing spatially coherent wavefronts out of two mirrors, separated by the MAM baseline, that feed directly into two siderostats that are parts of the TA. The two feed mirrors of the IIPS are articulated (in translation and tilt) in order to simulate stars located at different orientations in space, while still illuminating the TA siderostats. The spectrum of the simulated starlight of the IIPS corresponds to that of a blackbody at a temperature of about 3,100 K.

Goullioud, Renaud↗
NASA NTRS2012

The Aquarius Salinity Retrieval Algorithm

The first part of this presentation gives an overview over the Aquarius salinity retrieval algorithm. The instrument calibration [2] converts Aquarius radiometer counts into antenna temperatures (TA). The salinity retrieval algorithm converts those TA into brightness temperatures (TB) at a flat ocean surface. As a first step, contributions arising from the intrusion of solar, lunar and galactic radiation are subtracted. The antenna pattern correction (APC) removes the effects of cross-polarization contamination and spillover. The Aquarius radiometer measures the 3rd Stokes parameter in addition to vertical (v) and horizontal (h) polarizations, which allows for an easy removal of ionospheric Faraday rotation. The atmospheric absorption at L-band is almost entirely due to molecular oxygen, which can be calculated based on auxiliary input fields from numerical weather prediction models and then successively removed from the TB. The final step in the TA to TB conversion is the correction for the roughness of the sea surface due to wind, which is addressed in more detail in section 3. The TB of the flat ocean surface can now be matched to a salinity value using a surface emission model that is based on a model for the dielectric constant of sea water [3], [4] and an auxiliary field for the sea surface temperature. In the current processing only v-pol TB are used for this last step.

Meissner, Thomas↗
NASA NTRS2012

MSFC's Advanced Space Propulsion Formulation Task

In NASA s Fiscal Year 2012, a small project was undertaken to provide additional substance, depth, and activity knowledge to the technology areas identified in the In-Space Propulsion Systems Roadmap, Technology Area 02 (TA-02), as created under the auspices of the NASA Office of the Chief Technologist (OCT). This roadmap was divided into four basic groups: (1) Chemical Propulsion, (2) Non-chemical Propulsion, (3) Advanced (TRL<3) Propulsion Technologies, and (4) Supporting Technologies. The first two were grouped according to the governing physics. The third group captured technologies and physic concepts that are at a lower TRL level. The fourth group identified pertinent technical areas that are strongly coupled with these related areas which could allow significant improvements in performance. There were a total of 45 technologies identified in TA-02, and 25 of these were studied in this formulation task. The goal of this task was to provide OCT with a knowledge-base for decisionmaking on advanced space propulsion technologies and not waste money by unintentionally repeating past projects or funding the technologies with minor impacts. This formulation task developed the next level of detail for technologies described and provides context to OCT where investments should be made. The presentation will begin with the list of technologies from TA-02, how they were prioritized for this study, and details on what additional data was captured for the technologies studied. Following this, some samples of the documentation will be provided, followed by plans on how the data will be made accessible.

Huebner, Lawrence D.↗
NASA NTRS2014

Green Propulsion Auxiliary Power Unit Demonstration at MSFC

In 2012, the National Aeronautics & Space Administration (NASA) Space Technology Mission Directorate (STMD) began the process of building an integrated technology roadmap, including both technology pull and technology push strategies. Technology Area 1 (TA-01) for Launch Propulsion Systems is one of fourteen TA's that provide recommendations for the overall technology investment strategy and prioritization of NASA's space technology activities. Identified within TA-01 was the need for a green propulsion auxiliary power unit (APU) for hydraulic power by 2015. Engineers led by the author at the Marshall Space Flight Center (MSFC) have been evaluating green propellant alternatives and have begun the development of an APU testbed to demonstrate the feasibility of use. NASA has residual APU assets remaining from the retired Space Shuttle Program. Likewise, the F-16 Falcon fighter jet also uses an Emergency Power Unit (EPU) that has similar characteristics to the NASA hardware. Both EPU's and APU components have been acquired for testing at MSFC. In concert with this effort, ATK has been developing green propellant technology based on the Swedish Space Corp ECAPS LMP-103S propellant. Propellant blending and test facilities have been established at ATK's Elkton MD facility with the intent to provide suitable propellant blends for application to green APU systems as well as thrusters. This paper will summarize the status of the testing efforts with ATK for use of the green propellant LMP-103S based on ammonium dinitramide and use of the Air Force Research Laboratory (AFRL) propellant AF-M315E based on hydroxyl ammonium nitrate with these test assets.

Robinson, Joel W.↗
NASA NTRS2014

Green Mono Propulsion Activities at MSFC

In 2012, the National Aeronautics & Space Administration (NASA) Space Technology Mission Directorate (STMD) began the process of building an integrated technology roadmap, including both technology pull and technology push strategies. Technology Area 1 (TA-01) for Launch Propulsion Systems and TA-02 In-Space Propulsion are two of the fourteen TA's that provide recommendations for the overall technology investment strategy and prioritization of NASA's space technology activities. Identified within these documents are future needs of green propellant use. Green ionic liquid monopropellants and propulsion systems are beginning to be demonstrated in space flight environments. Starting in 2010 with the flight of PRISMA, a one Newton thruster system began on-orbit demonstrations operating on ammonium dinitramide based propellant. The NASA Green Propellant Infusion Mission (GPIM) plans to demonstrate both 1 N, and 22 N hydroxyl ammonium nitrate based thrusters in a 2015 flight demonstration. In addition, engineers at MSFC have been evaluating green propellant alternatives for both thrusters and auxiliary power units. This paper summarizes the status of these development/demonstration activities and investigates the potential for evolution of green propellants from small spacecraft and satellites to larger spacecraft systems, human exploration, and launch system auxiliary propulsion applications.

Robinson, Joel W.↗
NASA NTRS2020

Attribution of Chemistry-Climate Model Initiative (CCMI) Ozone Radiative Flux Bias from Satellites

The top-of-atmosphere (TOA) outgoing longwave flux over the 9.6-μm ozone band is a fundamental quantity for understanding chemistry-climate coupling. However, observed TOA fluxes are hard to estimate as they exhibit considerable variability in space and time that depend on the distributions of clouds, ozone (O3), water vapor (H2O), air temperature (Ta), and surface temperature (Ts). Benchmarking present day fluxes and quantifying the relative influence of their drivers is the first step for estimating climate feedbacks from ozone radiative forcing and predicting radiative forcing evolution. To that end, we constructed observational instantaneous radiative kernels (IRKs) under clear-sky conditions, representing the sensitivities of the TOA flux in the 9.6-μm ozone band to the vertical distribution of geophysical variables, including O3, H2O, Ta, and Ts based upon the Aura Tropospheric Emission Spectrometer (TES) measurements. Applying these kernels to present-day simulations from the Chemistry-Climate Model Initiative (CCMI) project as compared to a 2006 reanalysis assimilating satellite observations, we show that the models have large differences in TOA flux, attributable to different geophysical variables. In particular, model simulations continue to diverge from observations in the tropics, as reported in previous studies of the Atmospheric Chemistry Climate Model Inter-comparison Project (ACCMIP) simulations. The principal culprits are tropical mid and upper tropospheric ozone followed by tropical lower tropospheric H2O. Five models out of the eight studied here have TOA flux biases exceeding 100 mWm-2 attributable to tropospheric ozone bias. Another set of five models have flux biases over 50 mWm-2 due to H2O. On the other hand, Ta radiative bias is negligible in all models (no more than 30 mWm-2). We found that AM3 and CMAM have the lowest TOA flux biases globally but are a result of cancellation of opposite biases due to difference processes. Overall, the multi-model ensemble mean bias is –133±98 mWm-2, indicating that they are too atmospherically opaque due to trapping too much radiation in the atmosphere by overestimated tropical tropospheric O3 and H2O. Having too much O3 and H2O in the troposphere would have different impacts on the sensitivity of TOA flux to O3 and these competing effects add more uncertainties on the ozone radiative forcing. We find that the inter-model TOA outgoing longwave radiation (OLR) difference is well anti-correlated with their ozone band flux bias. This suggests that there is significant radiative compensation in the calculation of model outgoing longwave radiation.

Aura Tropospheric Emission Spectrometer (TES) meas↗
DOE OSTI2024

How to Design and Implement an Equitable Building Performance Standard: Lessons from the Building Performance Standards Technical Assistance Network

States and local governments seek to accomplish the intersecting goals of reducing greenhouse gas emissions, improving building operations, and bettering the daily lives of their communities. Building Performance Standards (BPS) have emerged as a critical policy lever to reach these intertwined climate and societal goals. These policies, if shaped and implemented well, have the chance to not only help reach our nation's climate, energy, and livability goals, but to do so with the active participation of those traditionally excluded from policy processes. This nascent policy movement provides jurisdictions across the country the opportunity to shape these policies from the outset to deliver comfort, health, and safety in our built environment for all. The US Department of Energy in partnership with our National Laboratories have been providing technical assistance for jurisdictions interested in, adopting, and implementing Building Performance Standards. Through this work, the BPS Technical Assistance Network (TA Network) has tracked and documented the innovative and equitable approaches to BPS across the country. The TA Network has crafted foundational technical analysis, such as building stock and emissions impacts, equity prioritization and peak load impacts, and aggregated cost benefit analysis. And by combining powerful technical analysis with dissemination of best practices resources to support equitable implementation, the TA Network provides jurisdictions with the tools and support necessary to embark on their ambitious policy goals.

building performance standards↗
DOE OSTI2024

Catalyst

Catalysts comprising a Ta layer having an outer layer with a layer comprising Pt directly thereon, wherein the Ta layer has an average thickness in a range from 0.04 to 30 nanometers, wherein the layer comprising Pt has an average thickness in a range from 0.04 to 50 nanometers, and wherein the Pt and Ta are present in an atomic ratio in a range from 0.01:1 to 10:1. Catalyst described herein are useful, for example, in fuel cell membrane electrode assemblies.

Steinbach, Andrew J. L.↗
DOE OSTI2021

New Mechanism for Yield Point Phenomena

Yield point phenomena (YPP) are widely attributed to discrete dislocation locking by solute atmospheres. An alternate YPP mechanism was recently suggested by simulations of Ta single crystals without any influence of solutes or discrete dislocations. The general meso-scale (GM) simulations consist of crystal plasticity (CP) plus accounting for internal stresses of geometrically necessary dislocation content. GM predicted the YPP while CP did not, suggesting a novel internal stress mechanism. The predicted YPP varied with crystal orientation and boundary conditions, contrary to expectations for a solute mechanism. The internal stress mechanism was probed by experimentally deforming oligocrystal Ta samples and comparing the results with independent GM simulations. Strain distributions of the experiments were observed with high-resolution digital image correlation. A YPP stress–strain response occurred in the 0–2% strain range in agreement with GM predictions. Shear bands appeared concurrent with the YPP stress–strain perturbation in agreement with GM predictions. At higher strains, the shear bands grew at progressively slower rates in agreement with GM predictions. It was concluded that the internal stress mechanism can account for the existence of YPP in a wide variety of materials including ones where interstitial-dislocation interactions and dislocation transient avalanches are improbable. Furthermore, the internal stress mechanism is a CP analog of various micro-scale mechanisms of discrete dislocations such as pile-up or bow-out. It may operate concurrently with strain aging, or either mechanism may operate alone. A suggestion was made for a future experiment to answer this question.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on TaSi2PH18C6(NCl3)2 by Materials Project

TaSi2C6PH18(NCl3)2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two TaSi2C6PH18(NCl3)2 clusters. Ta5+ is bonded in a 6-coordinate geometry to one N3- and five Cl1- atoms. The Ta–N bond length is 1.86 Å. There are a spread of Ta–Cl bond distances ranging from 2.34–2.80 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to three C4- and one N3- atom to form SiC3N tetrahedra that share a cornercorner with one SiC3N tetrahedra and a cornercorner with one PN2Cl2 tetrahedra. There is two shorter (1.87 Å) and one longer (1.88 Å) Si–C bond length. The Si–N bond length is 1.86 Å. In the second Si4+ site, Si4+ is bonded to three C4- and one N3- atom to form SiC3N tetrahedra that share a cornercorner with one SiC3N tetrahedra and a cornercorner with one PN2Cl2 tetrahedra. There is one shorter (1.87 Å) and two longer (1.88 Å) Si–C bond length. The Si–N bond length is 1.86 Å. There are six inequivalent C4- sites. In the first C4- site, C4- is bonded to one Si4+ and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the second C4- site, C4- is bonded to one Si4+ and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the third C4- site, C4- is bonded to one Si4+ and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the fourth C4- site, C4- is bonded to one Si4+ and three H1+ atoms to form distorted corner-sharing CSiH3 tetrahedra. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the fifth C4- site, C4- is bonded to one Si4+ and three H1+ atoms to form distorted corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. In the sixth C4- site, C4- is bonded to one Si4+ and three H1+ atoms to form corner-sharing CSiH3 tetrahedra. All C–H bond lengths are 1.10 Å. P5+ is bonded to two N3- and two Cl1- atoms to form PN2Cl2 tetrahedra that share corners with two SiC3N tetrahedra. There is one shorter (1.58 Å) and one longer (1.62 Å) P–N bond length. Both P–Cl bond lengths are 2.03 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to two Si4+ and one P5+ atom. In the second N3- site, N3- is bonded in a bent 150 degrees geometry to one Ta5+ and one P5+ atom. There are eighteen inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fourteenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fifteenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the sixteenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the seventeenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eighteenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one P5+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Ta5+ atom. In the third Cl1- site, Cl1- is bonded in a water-like geometry to two equivalent Ta5+ atoms. In the fourth Cl1- site, Cl1- is bonded in a single-bond geometry to one P5+ atom. In the fifth Cl1- site, Cl1- is bonded in a single-bond geometry to one Ta5+ atom. In the sixth Cl1- site, Cl1- is bonded in a single-bond geometry to one Ta5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3B4 by Materials Project

Ta3B4 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Ta4+ sites. In the first Ta4+ site, Ta4+ is bonded to twelve B3- atoms to form a mixture of edge and face-sharing TaB12 cuboctahedra. There are eight shorter (2.46 Å) and four longer (2.50 Å) Ta–B bond lengths. In the second Ta4+ site, Ta4+ is bonded in a 7-coordinate geometry to seven B3- atoms. There are a spread of Ta–B bond distances ranging from 2.37–2.55 Å. There are two inequivalent B3- sites. In the first B3- site, B3- is bonded in a 9-coordinate geometry to seven Ta4+ and two equivalent B3- atoms. Both B–B bond lengths are 1.85 Å. In the second B3- site, B3- is bonded in a 9-coordinate geometry to six Ta4+ and three B3- atoms. The B–B bond length is 1.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsCa2Ta3O10 by Materials Project

CsCa2Ta3O10 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Cs1+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Cs–O bond lengths are 3.26 Å. Ca2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Ca–O bond distances ranging from 2.52–3.03 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There is two shorter (1.97 Å) and four longer (1.98 Å) Ta–O bond length. In the second Ta5+ site, Ta5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ta–O bond distances ranging from 1.80–2.30 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to four equivalent Cs1+ and one Ta5+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a linear geometry to four equivalent Ca2+ and two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to four equivalent Ca2+ and two Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2Ta2O7 by Materials Project

Sr2Ta2O7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. There are four shorter (2.51 Å) and two longer (2.59 Å) Sr–O bond lengths. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight TaO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.65–2.88 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 10–16°. There are a spread of Ta–O bond distances ranging from 1.88–2.17 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with six equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–12°. There are a spread of Ta–O bond distances ranging from 1.92–2.09 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to three equivalent Sr2+ and two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two Ta5+ atoms. In the fourth O2- site, O2- is bonded to three equivalent Sr2+ and one Ta5+ atom to form a mixture of distorted edge and corner-sharing OSr3Ta tetrahedra. In the fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Sr2+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaN by Materials Project

TaN crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Ta3+ sites. In the first Ta3+ site, Ta3+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All Ta–N bond lengths are 2.05 Å. In the second Ta3+ site, Ta3+ is bonded to six equivalent N3- atoms to form a mixture of distorted corner, edge, and face-sharing TaN6 pentagonal pyramids. All Ta–N bond lengths are 2.18 Å. N3- is bonded to five Ta3+ atoms to form a mixture of distorted corner and edge-sharing NTa5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2Ta2O7 by Materials Project

Sr2Ta2O7 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight TaO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.65–2.92 Å. In the second Sr2+ site, Sr2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.62 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with six equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–15°. There are a spread of Ta–O bond distances ranging from 1.91–2.10 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 6–16°. There are a spread of Ta–O bond distances ranging from 1.88–2.18 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Sr2+ and one Ta5+ atom to form distorted corner-sharing OSr3Ta tetrahedra. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Sr2+ and two Ta5+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Sr2+ and two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to three equivalent Sr2+ and two equivalent Ta5+ atoms. In the fifth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Ta5+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two Ta5+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Sr2+ and one Ta5+ atom.

36 MATERIALS SCIENCE↗