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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

High-Pressure Effects on an Octa-Hydrated Curium Complex: An Experimental and Theoretical Investigation

An octa-hydrated curium compound [Cm(H 2 O) 8 ](Hdtp)(dtp)·H 2 O (Cm1,H 2 dtp = 2,3-di(tetrazol-5-yl)pyrazine) along with its lanthanide analogues [Ln(H 2 O) 8 ](Hdtp)-(dtp)·H 2 O (Ln1, Ln 3+ = La 3+ –Nd 3+ , Sm 3+ –Lu 3+ ) were synthesized and characterized using single crystal X-ray diffraction and spectroscopic methods. Bond length analysis of VIII Cm(III)–OH 2 (where VIII refers to the coordination number) was compared to VIII Ln(III)–OH 2 (Ln 3+ = Nd 3+ and Sm 3+ ), indicating similar VIII M(III)–OH 2 bond lengths owing to the similar eight-coordinate ionic radii of these VIII M(III) cations. Owing to the reduced coordination number, the VIII Cm(III)–OH 2 bond lengths were shorter than previously reported IX Cm(III)–OH 2 bonds in [Cm(H 2 O) 9 ](CF 3 SO 3 ) 3 . The octa-aquo complexes were also characterized by solid-state UV–vis–NIR spectroscopy in addition to variable-temperature and variable-pressure photoluminescence. Variable-pressure absorption spectra of Cm1 were compared with Ln1 and show that the Cm(III) f → f transitions have a stronger dependence on pressure than that observed in Ln1 (Ln 3+ = Nd 3+ and Sm 3+ ). The experimental and computational analyses reveal that the monotonic decrease in the computed energy difference between the ground state and the first excited state corresponds to the observed red shift of the photoluminescence peak. This is accompanied by a gradual reduction in the average Cm(III)–OH 2 bond length and a delocalization of spin densities, alongside an intensified interaction involving the 5f orbitals under increasing pressure. Furthermore, these changes accommodate the new geometry and collectively modify the energy landscape, resulting in peak broadening and quenching.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1998

Investigation of Third Order Optical Nonlinearity and Reverse Saturable Absorption of Octa-alkoxy Metallophthalocyanines

In recent years, there has been a growing interest in the development of passive optical power limiters for the protection of the human eye and solid-state sensors from damage caused by energetic light pulses and also for other switching applications. One of the key issues involved is the search for appropriate materials that show effective reverse saturable absorption. Phthalocyanines seem to be good candidates for such applications because of their higher third order nonlinearity and the unique electronic absorption characteristics. A series of 1,4,8,11,15, 18,22,25-octa-alkoxy metallophthalocyanines containing various central metal atoms such as zinc, copper, palladium, cobalt and nickel were characterized for their third order nonlinearity and for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers.

Sanghadasa, Mohan↗
NASA NTRSDate not supplied

J-OCTA Applications to in Space Manufacturing and Nanofluidic Technologies

We consider examples of J-OCTA software application to physics-based analysis of in-space manufacturing technologies. Firstly, we consider an atomistic model of thermal welding at the polymer-polymer interface for applications to 3D manufacturing by following diffusion of polymer chains. We show that each component of the polymer blend has its own characteristic time of diffusion and that both strain–stress and shear viscosity curves agree with experimental data. Next, nonlinear shrinkage of the metal part during manufacturing by bound metal deposition under microgravity, is considered using a multi-scale physics-based approach that spans from atomistic dynamics to full-part shrinkage. At the smallest scale we use atomistic dynamics to simulated sintering of a few Ti6Al4V nanoparticles, study sintering mechanisms and estimate important parameters including grain boundary width and diffusion rates of the atoms at the surface that are used at the other scales of modelling. Finally, we analyse selective ionic conduction through an artificial nanopore in a graphene sheet motivated by applications to desalination and energy harvesting. We build distributions of the number and orientation of water molecules in the ion’s hydration shells providing novel insight into the ion-water-carbon interaction at the nanopore.

molecular dynamics↗
DOE OSTI2022

Orange County Transportation Authority Fuel Cell Electric Bus Progress Report - Data Period Focus: Feb. 2020 through Jul. 2021 [Slides]

This report presents early results from a deployment of fuel cell electric buses (FCEBs) operated by Orange County Transportation Authority (OCTA) in Southern California. The ten FCEBs, produced by New Flyer, feature an electric drive propulsion system powered by a Ballard fuel cell system. The project team is collaborating with the U.S. Department of Energy (DOE) and DOE's National Renewable Energy Laboratory (NREL) to evaluate the buses in revenue service. The goal of this evaluation is to compare the FCEB performance to that of conventional technology and to track progress over time toward meeting the technical targets set by DOE and the Department of Transportation (DOT). The FCEBs were delivered beginning in late-2019, and were placed in service on February 9, 2020. The data period covers February 2020 through July 2021. NREL collects data on ten 2016 model year compressed natural gas (CNG) buses as a baseline comparison at OCTA.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

Orange County Transportation Authority Fuel Cell Electric Bus Progress Report (Feb-Jul 2020) [Slides]

This report presents early results from a deployment of fuel cell electric buses (FCEBs) operated by Orange County Transportation Authority (OCTA) in Southern California. The ten FCEBs, produced by New Flyer, feature an electric drive propulsion system powered by a Ballard fuel cell system. The project team is collaborating with the U.S. Department of Energy (DOE) and DOE's National Renewable Energy Laboratory (NREL) to evaluate the buses in revenue service. The goal of this evaluation is to compare the FCEB performance to that of conventional technology and to track progress over time toward meeting the technical targets set by DOE and the Department of Transportation (DOT). The FCEBs were delivered beginning in late-2019, and were placed in service on February 9, 2020. The data period covers February 2020 through July 2020. NREL collects data on ten 2016 model year compressed natural gas (CNG) buses as a baseline comparison at OCTA.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2021

Fuel Cell Buses in U.S. Transit Fleets: Current Status 2020

This report summarizes the progress of fuel cell electric bus (FCEB) development in the United States and discusses the achievements and challenges of introducing fuel cell propulsion in transit. The report provides a summary of results from evaluations performed by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL). The 2020 summary results primarily focus on the most recent data on these FCEBs, from January 2020 through July 2020. The primary results presented in the report are from 25 FCEBs deployed at three agencies: Alameda-Contra Costa Transit District (AC Transit) in Oakland, California (10 FCEBs); Orange County Transportation Authority (OCTA) in Santa Ana, California (10 FCEBs); SunLine Transit Agency in Thousand Palms, California (5 FCEBs).

08 HYDROGEN↗
DOE OSTI2020

Over 15% Efficiency Polymer Solar Cells Enabled by Conformation Tuning of Newly Designed Asymmetric Small‐Molecule Acceptors

Abstract The prosperous period of polymer solar cells (PSCs) has witnessed great progress in molecule design methods to promote power conversion efficiency (PCE). Designing asymmetric structures has been proved effective in tuning energy level and morphology, which has drawn strong attention from the PSC community. Two hepta‐ring and octa‐ring asymmetric small molecular acceptors (SMAs) (IDTP‐4F and IDTTP‐4F) with S‐shape and C‐shape confirmations are developed to study the relationship between conformation shapes and PSC efficiencies. The similarity of absorption and energy levels between two SMAs makes the conformation a single variable. Additionally, three wide‐bandgap polymer donors (PM6, S1, and PM7) are chosen to prove the universality of the relationship between conformation and photovoltaic performance. Consequently, the champion PCE afforded by PM7: IDTP‐4F is as high as 15.2% while that of PM7: IDTTP‐4F is 13.8%. Moreover, the S‐shape IDTP‐4F performs obviously better than their IDTTP‐4F counterparts in PSCs regardless of the polymer donors, which confirms that S‐shape conformation performs better than the C‐shape one. This work provides an insight into how conformations of asymmetric SMAs affect PCEs, specific functions of utilizing different polymer donors to finely tune the active‐layer morphology and another possibility to reach an excellent PCE over 15%.

Guo, Qing↗
DOE OSTI2023

Induction and Stabilization of Columnar Mesophases in Fluorinated Polycyclic Aromatic Hydrocarbons by Arene‐Perfluoroarene Interactions

Abstract The straightforward synthesis of several Fluorinated Polycyclic Aromatic Hydrocarbons by the efficient, transition‐metal‐free, arene fluorine nucleophilic substitution reaction is described, and the full investigation of their liquid crystalline and optical properties reported. The key precursors for this study, i. e. 2,2’‐dilithio‐4,4′,5,5′‐tetraalkoxy‐1,1’‐biphenyl derivatives, were obtained in two steps from the highly selective Scholl oxidative homo‐coupling of 3,4‐dialkoxy‐1‐bromobenzene, followed by quantitative double‐lithiation. In situ room temperature nucleophilic annulation with either perfluorobenzene or perfluoronaphthalene leads to 1,2,3,4‐tetrafluoro‐6,7,10,11‐tetraalkxoytriphenylenes and 9,10,11,12,13,14‐hexafluoro‐2,3,6,7‐tetraalkoxybenzo[f]tetraphenes, respectively, in good yields. Exploiting the same strategy, subsequent double annulations resulted in the formation of 9,18‐difluoro‐2,3,6,7,11,12,15,16‐octa(alkoxy)tribenzo[f,k,m]tetraphenes and 9,10,19,20‐tetrafluoro‐2,3,6,7,12,13,16,17‐octakis(hexyloxy)tetrabenzo[a,c,j,l]tetracenes, respectively. Despite the presence of only four alkoxy chains, the polar “Janus” mesogens display a columnar hexagonal mesophase over broad temperature ranges, with higher mesophase stability than the archetypical 2,3,6,7,10,11‐hexa(alkoxy)triphenylenes and their hydrogenated counterparts. The improvement or induction of mesomorphism is attributed to efficient antiparallel face‐to‐face π‐stacking driven by the establishment of non‐covalent perfluoroarene‐arene intermolecular interactions. The larger lipophilic discotic π‐extended compounds also exhibit columnar mesomorphism, over similar temperature ranges and stability than their hydrogenated homologs. Finally, these fluorinated molecules form stringy gels in various solvents, and show interesting solvatochromic emission properties in solution as well as strong emission in thin films and gels.

Chemistry↗
DOE OSTI2023

Dispersed Nickel Phthalocyanine Molecules on Carbon Nanotubes as Cathode Catalysts for Li-CO 2 Batteries

The Li-CO 2 battery has great potential for both CO 2 utilization and energy storage, but its practical application is limited by low energy efficiency and short cycle life. Efficient cathode catalysts are needed to address this issue. Herein, this work reports on molecularly dispersed electrocatalysts (MDEs) of nickel phthalocyanine (NiPc) anchored on carbon nanotubes (CNTs) as the cathode catalyst for Li-CO 2 batteries. The dispersed NiPc molecules efficiently catalyze CO 2 reduction, while the conductive and porous CNTs networks facilitate CO 2 evolution reaction, leading to enhanced discharging and charging performance compared to the NiPc and CNTs mixture. Octa-cyano substitution on NiPc (NiPc-CN) further enhances the interaction between the molecule and CNTs, resulting in better cycling stability. The Li-CO 2 battery with the NiPc-CN MDE cathode shows a high discharge voltage of 2.72 V and a small discharging–charging potential gap of 1.4 V, and can work stably for over 120 cycles. The reversibility of the cathode is confirmed by experimental characterizations. Finally, this work lays a foundation for the development of molecular catalysts for Li-CO 2 battery cathodes.

25 ENERGY STORAGE↗
DOE OSTI2026

Extraction, Characterization, and Stability Studies of Bistriazinyl-Derived Carboxylic Acids

Separation of An(III) and Ln(III) ions will benefit the recycling of used nuclear fuel (UNF). For this purpose, many ligands have been tested over the years, and several separation processes have been successfully demonstrated on the laboratory scale. Current research aims at the development of new ligands that are built only with carbon, hydrogen, oxygen, and nitrogen (CHON), as they can be incinerated completely without secondary waste production. Here, we tested a new class of water-soluble ligands, the bistriazinyl-octa-carboxylic acids. One member, in particular, 2,6-bis-[5,6-di(3,4-dicarboxyphenyl)-1,2,4- triazin-3-yl]-pyridine (BTPOA), was found to be suitable for the selective separation of Am(III) and Cm(III) ions from Ln(III) ions and may act as a CHON alternative to its sulfonated analogue (SO 3 -Ph-BTP). BTPOA exhibited good extraction results and a high selectivity for Am(III) over Eu(III) ions. This ligand’s complexation of metal ions was further studied using potentiometric spectroscopy, as well as time-resolved laser-induced spectroscopy with Cm(III) and Eu(III) in aqueous HClO 4 and HNO 3 media. Conditional stability constants of each formed species were determined. In the HClO 4 system, Cm(III) formed three species (1:1, 1:2, and 1:3) through the stepwise addition of a single BTPOA molecule. On the other hand, in HNO 3 , Cm(III) formed two 1:2 complexes and one 1:3 complex, while the stepwise formation of three species was observed for Eu(III). The stability constants are comparable to the values for SO 3 -Ph-BTP. The radiolytic behavior of BTPOA was also investigated using electron pulse irradiation measurements to determine absolute rate coefficients (k) under ambient temperature conditions for the reaction of BTPOA with typical UNF reprocessing radical radiolysis products the hydrated electron (e aq − , k = (1.60 ± 0.02) × 10 10 M −1 s −1 ), the hydrogen atom (H • , k = (2.17 ± 0.03) × 10 9 M −1 s −1 ), and hydroxyl ( • OH, k = (6.95 ± 0.06) × 10 9 M −1 s −1 ) and nitrate (NO 3 • , k = (0.37 ± 0.02) × 10 7 M −1 s−1) radicals. These rate coefficients indicate that the radiolytic longevity of BTPOA should increase with HNO 3 concentration, owing to the consumption of e aq − /H • , by nitrate anions, and the replacement of • OH by the less reactive NO 3 • .

Diaz Gomez, Laura [Forschungszentrum Juelich (Germ↗
DOE OSTI2025

Probing the Redox Reactivity of Alkyl Bound Astatine: A Study on the Formation and Cleavage of a Stable At–C Bond

The formation of a stable alkyl At–C bond occurs during the shipment of 211 At on a 3-octanone-impregnated column and the reactivity of 211 At stripped from columns has been studied. The 211 At could not be recovered from the 3-octanone organic phase using nitric acid or sodium hydroxide, even up to 10 and 15.7 M, respectively. Several reducing and oxidizing agents, including hydrazine, hydroxylamine, ascorbic acid, ceric ammonium nitrate, potassium permanganate, sodium hypochlorite, and calcium hypochlorite were used to promote the recovery of 211 At. The most effective reducing agent was hydroxylamine, where ~70% of the 211 At was recovered, while among oxidizing agents ceric ammonium nitrate, potassium permanganate, and sodium hypochlorite all showed near quantitative recovery of 211 At. These results indicate an At–C bond is being formed during the shipment of the column and a redox reaction is required for bond cleavage to occur. Furthermore, DFT calculations have been used to propose several products of an AtO + -3-octanone reaction, with 4-astato-5-hydroxy-octa-3-one being the most probable.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Transformation of CeO 2 Nanoparticles into Atomically Dispersed Ce Cations Leads to Enhanced Reactivity for Automotive Emissions Control

Nanosized cerium oxide (CeO 2 ) has been extensively used as the oxygen storage component in automotive emission control systems. However, the possible influence of atomically dispersed Ce in these catalysts has not been recognized. Here, in this study, we demonstrate the controllable transformation of ceria nanoparticles into isolated cerium cations on γ-Al 2 O 3 via reductive atom trapping in 10% H 2 at 800 °C, achieving over half-monolayer coverage. Dispersed Ce 1 ions anchored by surface penta- and octa-coordinated Al sites exhibit outstanding thermal stability in air up to 500 °C, enabling further loading of active metals with well-defined catalyst structures. With this strategy, supported single-atom Rh 1 surrounded by dispersed Ce 1 is confirmed to exhibit much superior performance to Rh 1 on bare Al 2 O 3 or nanocrystalline CeO 2 in catalyzing NO reduction by CO, exhibiting a striking one-order-of-magnitude increase in activity. Dispersed Ce 1 exhibits greatly enhanced oxygen transfer capability compared to ceria nanoparticles and introduces a modified reaction mechanism that involves an adjacent Rh 1 –Ce 1 motif, resulting in a greatly decreased activation barrier (from 192 to 96 kJ/mol). The reactivity enhancements are also seen with Ce 1 -promoted Pt nanoparticles for oxidation of CO and hydrocarbons.

Jiang, Dong [Washington State Univ., Pullman, WA (↗
DOE OSTI2020

Materials Data on Ca(La2Se3)4 by Materials Project

Ca(La2Se3)4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to eight Se2- atoms to form distorted CaSe8 hexagonal bipyramids that share corners with eight LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, and faces with eight LaSe8 hexagonal bipyramids. There are a spread of Ca–Se bond distances ranging from 3.01–3.29 Å. In the second Ca2+ site, Ca2+ is bonded to eight Se2- atoms to form distorted CaSe8 hexagonal bipyramids that share corners with eight LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, and faces with eight LaSe8 hexagonal bipyramids. There are a spread of Ca–Se bond distances ranging from 3.02–3.28 Å. There are sixteen inequivalent La+2.75+ sites. In the first La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, an edgeedge with one CaSe8 hexagonal bipyramid, edges with three LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.27 Å. In the second La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with two CaSe8 hexagonal bipyramids, corners with six LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.06–3.26 Å. In the third La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, an edgeedge with one CaSe8 hexagonal bipyramid, edges with three LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.06–3.25 Å. In the fourth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with two CaSe8 hexagonal bipyramids, corners with six LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.06–3.26 Å. In the fifth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with eight LaSe8 hexagonal bipyramids, edges with two equivalent CaSe8 hexagonal bipyramids, edges with two LaSe8 hexagonal bipyramids, and faces with eight LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.04–3.26 Å. In the sixth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.03–3.25 Å. In the seventh La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with eight LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, faces with two CaSe8 hexagonal bipyramids, and faces with six LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.06–3.28 Å. In the eighth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.29 Å. In the ninth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with eight LaSe8 hexagonal bipyramids, edges with two equivalent CaSe8 hexagonal bipyramids, edges with two LaSe8 hexagonal bipyramids, and faces with eight LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.25 Å. In the tenth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with two CaSe8 hexagonal bipyramids, corners with six LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.28 Å. In the eleventh La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, an edgeedge with one CaSe8 hexagonal bipyramid, edges with three LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.29 Å. In the twelfth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with two CaSe8 hexagonal bipyramids, corners with six LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.03–3.27 Å. In the thirteenth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.27 Å. In the fourteenth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with eight LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, faces with two CaSe8 hexagonal bipyramids, and faces with six LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.06–3.26 Å. In the fifteenth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, edges with four LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.05–3.26 Å. In the sixteenth La+2.75+ site, La+2.75+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share a cornercorner with one CaSe8 hexagonal bipyramid, corners with seven LaSe8 hexagonal bipyramids, an edgeedge with one CaSe8 hexagonal bipyramid, edges with three LaSe8 hexagonal bipyramids, a faceface with one CaSe8 hexagonal bipyramid, and faces with seven LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.06–3.26 Å. There are twenty-four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to six La+2.75+ atoms to form distorted SeLa6 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeLa6 octahedra, and faces with five SeLa6 octahedra. The corner-sharing octahedra tilt angles range from 16–51°. In the second Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeLa6 octahedra, and faces with five SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 17–50°. In the third Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeLa6 octahedra, and faces with five SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 16–51°. In the fourth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form a mixture of distorted corner, edge, and face-sharing SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 17–51°. In the fifth Se2- site, Se2- is bonded to six La+2.75+ atoms to form distorted SeLa6 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeCaLa5 octahedra, and faces with five SeLa6 octahedra. The corner-sharing octahedra tilt angles range from 17–51°. In the sixth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeCaLa5 octahedra, and faces with five SeLa6 octahedra. The corner-sharing octahedra tilt angles range from 16–51°. In the seventh Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form a mixture of distorted corner, edge, and face-sharing SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 17–51°. In the eighth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeLa6 octahedra, edges with six SeLa6 octahedra, and faces with five SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 17–51°. In the ninth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeLa6 octahedra, and faces with five SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 16–50°. In the tenth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form a mixture of distorted corner, edge, and face-sharing SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 16–51°. In the eleventh Se2- site, Se2- is bonded to six La+2.75+ atoms to form distorted SeLa6 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeCaLa5 octahedra, and faces with five SeLa6 octahedra. The corner-sharing octahedra tilt angles range from 17–51°. In the twelfth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form a mixture of distorted corner, edge, and face-sharing SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 16–50°. In the thirteenth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeCaLa5 octahedra, and faces with five SeLa6 octahedra. The corner-sharing octahedra tilt angles range from 18–51°. In the fourteenth Se2- site, Se2- is bonded to six La+2.75+ atoms to form distorted SeLa6 octahedra that share corners with fifteen SeCaLa5 octahedra, edges with six SeCaLa5 octahedra, and faces with five SeLa6 octahedra. The corner-sharing octahedra tilt angles range from 16–51°. In the fifteenth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeLa6 octahedra, edges with six SeCaLa5 octahedra, and faces with five SeCaLa5 octahedra. The corner-sharing octahedra tilt angles range from 16–51°. In the sixteenth Se2- site, Se2- is bonded to one Ca2+ and five La+2.75+ atoms to form distorted SeCaLa5 octahedra that share corners with fifteen SeLa6 octahedra, edges with six SeLa6 octa

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ab Initio Calculations on the Ground and Excited Electronic States of Thorium–Ammonia, Thorium–Aza-Crown, and Thorium–Crown Ether Complexes

Positively charged metal–ammonia complexes are known to host peripheral, diffuse electrons around their molecular skeleton. The resulting neutral species form materials known as expanded or liquid metals. Alkali, alkaline earth, and transition metals have been investigated previously in experimental and theoretical studies of both the gas and condensed phase. This work is the first ab initio exploration of an f-block metal–ammonia complex. The ground and excited states are calculated for Th0–3+ complexes with ammonia, crown ethers, and aza-crown ethers. For Th3+ complexes, the one valence electron Th populates the metal’s 6d or 7f orbitals. For Th0–2+, the additional electrons prefer occupation of the outer s- and p-type orbitals of the complex, except Th(NH3)10, which uniquely places all four electrons in outer orbitals of the complex. Although thorium coordinates up to ten ammonia ligands, octa-coordinated complexes are more stable. Crown ether complexes have a similar electronic spectrum to ammonia complexes, but excitations of electrons in the outer orbitals of the complex are higher in energy. Aza-crown ethers disfavor the orbitals perpendicular to the crowns, attributed to the N-H bonds pointing along the plane of the crowns.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1995

Data archive for NO(y) from observations and construction and testing of airborne instrument for simultaneous measurement of NO, NO2, NO(y), and O3

The compilation and archiving of NO(x) and NO(y) measurements began in mid-March 1994. Since the submission of the first report, data summaries have been obtained for the TROPOZ 2, STRATOZ 3, OCTA and TOR/Schauinsland campaigns, and the full data sets will become a part of this archive in the near future. Climatologies of NO(x) and NO(y) have been developed from these and previously archived data sets, including the available GTE campaigns (ABLE-2A, B, -3A, B, CITE-2, -3, TRACE-A, PEM WEST-A) and AASE 1 and 2. The data have been grouped by season and altitude (boundary layer and 3 km ranges in the free troposphere). Maps showing median values of midday NO, NO(x) and NO(y) have been produced for each season for the boundary layer and 3 km ranges of the free troposphere. The statistics of the data (median, mean, and standard deviation, central 67% and 90%) have also been determined, and are shown in representative figures included in this report.

Carroll, Mary Anne↗
NASA NTRS1996

Determination of 2,3,7,8-chlorine-substituted dibenzo-p-dioxins and -furans at the part per trillion level in United States beef fat using high-resolution gas chromatography/high-resolution mass spectrometry

As part of the U.S. EPA Dioxin Reassessment Program, the 2,3,7,8-chlorine-substituted dibenzo-p-dioxins and furans were measured at part per trillion (ppt) levels in beef fat collected from slaughter facilities in the United States. This is the first statistically designed national survey of these compounds in the U.S. beef supply. Analyte concentrations were determined by high-resolution gas chromatography/high-resolution mass spectrometry, using isotope dilution methodology. Method limits of detection on a whole weight basis were 0.05 ppt for TCDD and 0.10 ppt for TCDF, 0.50 ppt for the pentas (PeCDDs/PeCDFs)/hexas (HxCDDs/HxCDFs)/heptas (HpCDDs/HpCDFs), and 3.00 ppt for the octas (OCDD/OCDF). Method detection and quantitation limits were established on the basis of demonstrated performance criteria utilizing fortified samples rather than by conventional signal-to-noise or variability of response methods. The background subtraction procedures developed for this study minimized the likelihood of false positives and increased the confidence associated with reported values near the detection limits. Mean and median values for each of the 2,3,7,8-Cl-substituted dioxins and furans are reported, along with the supporting information required for their interpretation. The mean toxic equivalence values for the samples are 0.35 ppt (nondetects = 0) and 0.89 ppt (nondetects = 1/2 LOD).

Benzofurans/analysis↗