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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Magnetothermal properties of Ho 1-x Dy x Al 2 (x = 0, 0.05, 0.10, 0.15, 0.25 and 0.50) compounds

Magnetic and magnetocaloric properties of H o 1 - x D y x A l 2 compounds with x = 0 , 0.05 , 0.10 , 0.15 , 0.25 and 0.50 , modelled using a Hamiltonian that includes the exchange interactions between Ho-Dy, Ho-Ho and Dy-Dy ions in addition to the crystalline electric field and the Zeeman effects, have been compared with those determined experimentally. In order to reproduce experimentally observed global ferromagnetic ordering temperatures and spin reorientation transition temperatures as x Dy varies, the exchange interactions between Ho-Dy and Ho-Ho were set as free parameters and adjusted to match the experimental results. We demonstrate that heat capacity of polycrystalline materials in non-zero magnetic fields can be satisfactory reproduced by using the average of multiple magnetic field directions with respect to the crystallographic coordinate system, while reasonably good agreement between experimentally determined and theoretically predicted magnetocaloric effects can be achieved considering an average of only three field directions.

36 MATERIALS SCIENCE↗
NASA NTRS1996

Theoretical Studies of the HO/HO2 Catalytic Cycle for Ozone Destruction

Recently it has been determined that the HO/HO2 catalytic cycle accounts for nearly one-half of the total ozone depletion in the lower stratosphere. The catalytic cycle is: (1) HO + O3 yields HO2 + O2; (2) HO2 + O3 yields HO + O2 + O2. The net reaction is 2O3 yields 3O2. The rate limiting step in this process is the reaction of HO2 with ozone. There is a problem extending the experimental measurement of the rate of this reaction over the range 233-400 K down to stratospheric temperatures of 210-220 K. Therefore we have undertaken a project to determine the temperature dependence of the rate constant for this reaction in the low temperature region. The first step in this project, which is described in this poster, is the determination of the relevant potential energy surfaces. The calculations use CASSCF/derivative methods to define the pathways followed by CASSCF/ACPF to determine the energetics. The HO + O3 reaction is found to proceed through an HO4 complex, which is unstable with respect to HO2 + O2. The HO2 +O3 reaction is more complex. One pathway, which has been characterized, is the formation of an HO5 complex which decomposes to HO3 + O2 and subsequently to HO + O2 + O2. Another pathway, which is believed to also play a role, is hydrogen abstraction to give O2 + HO3 and subsequent decomposition of HO3 to HO + O2. Isotopic labeling experiments indicate that the later pathway is dominant. However, so far attempts to locate the saddle point for this pathway have not been successful. We have also characterized the potential energy surfaces for a number of species involved in these reactions, including HO3 and triplet O4. The triplet O4 species is probably involved in the reaction of vibrationally excited O2 with ground state O2 leading to O3 + O. The latter reaction is believed to be important as an additional source of stratospheric ozone.

Walch, Stephen P.↗
NASA NTRS2002

Double-Pulsed 2-micron Laser Transmitter for Multiple Lidar Applications

A high energy double-pulsed Ho:Tm:YLF 2-micron laser amplifier has been demonstrated. 600 mJ per pulse pair under Q-switch operation is achieved with the gain of 4.4. This solid-state laser source can be used as lidar transmitter for multiple lidar applications such as coherent wind and carbon dioxide measurements.

Singh, Upendra N.↗
DOE OSTI2022

Trace Compound Analysis in TATB by Liquid Chromatography coupled with Spectroscopic and Spectrometric Detection

Accurate quantitation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is important because of its strategic use as an energetic material. A purity determination is also needed for the proper assessment of performance. A fast and sensitive method has been developed to measure the purity of TATB in polymer-bonded materials. The target material is extracted with DMSO, and the extract is separated on a reversed-phase chromatography column. The column effluent is monitored by diode array detection (DAD) at 354 nm. The characteristic UV-Vis response and retention time identify the individual components when compared to pure compound standards. The chemical structures of compounds with no pure standards available have been determined by high-resolution mass spectrometry (MS) and MS/MS. The major component, TATB, along with 1-chloro-3,5-dinitro-2,4,6-triaminobenzene (T4A) and mono-benzofuroxan (FX1) were quantitated directly from pure compound standards. Several trace concentration components, mono-benzofurazan (F1), 1-bromo-3,5-dinitro-2,4,6-triaminobenzene (Br-T4A), 2,4,6-triamino-1-nitroso-3,5-dinitrobenzene (MN-TATB), 2,4,6-triamino-1-hydroxyl-3,5-dinitrobenzene (HO-TATB), and 2,4,6-triamino-1-nitrile-3,5-dinitrobenzene (Nitrile-TATB) were also detected and structures verified via MS/MS. Approximate concentrations were determined using calibrations from standards of similar structures. Additional trace components were also detected by MS. Contained herein are the results of analyses of TATB-based materials characterized for polymer-bonded formulations compared to different preparations of TATB. The accuracy, details, and process of developing this method are reported here.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides

High-entropy rare-earth (RE) sesquioxides (RE 2 O 3 ) containing five cations in equimolar amounts have been investigated for a variety of applications, but little is known about their polymorphic behavior and coefficient of thermal expansion. Here, in this work, we evaluate the effect of the average ionic radius (AIR) on the polymorphism of high-entropy RE 2 O 3 . Powder samples of compositions 1 (Lu,Y,Ho,Nd,La) 2 O 3 (AIR = 0.938 Å) and 2 (Gd,Eu,Sm,Nd,La) 2 O 3 (AIR = 0.982 Å) were synthesized via a wet chemical method, and bead samples were prepared for aerodynamic levitation by melting the powders in a copper hearth. Structural transitions were monitored upon cooling from the melt to 1000 °C via in situ X-ray diffraction on aerodynamically levitated samples. The phase evolution was liquid, hexagonal H-type, and monoclinic B-type for composition 1 and liquid, cubic X-type, H-type, and B-type for composition 2. Based on their AIR, the general polymorphic transformations of the high-entropy RE 2 O 3 follow the trend of single-RE RE 2 O 3 , but the transition temperatures differ from those of single-RE RE 2 O 3 . The coefficient of thermal expansion values of the B-type phase of compositions 1 and 2 are similar to those of Gd 2 O 3 and previously published high-entropy RE 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs 2 NaLn(PS 4 ) 2 (Ln = La–Nd, Sm, and Gd–Ho)

The effect of the lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations was obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs 2 NaLn(PS 4 ) 2 (Ln = La–Nd, Sm, Gd–Ho) were grown as large single crystals (~0.1–1 mm 3 ) and characterized using single crystal X-ray diffraction and magnetic susceptibility measurements. Moving across the series, the structural studies revealed a change in the lanthanide coordination environment dependent upon the identity of the lanthanide. Although all compounds in the Cs 2 NaLn(PS 4 ) 2 series crystallize in the same space group and have the same Wyckoff positions of the atoms, a slight size change between Sm 3+ and Gd 3+ causes a subtle change in coordination number from 9 (for Ln = La–Sm) to 8 (for Ln = Gd–Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Finally, magnetic measurements performed on the Cs 2 NaLn(PS 4 ) 2 (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1999

High Efficiency End-Pumped Ho:Tm:YLF Disk Amplifier

Space based coherent lidar for global wind measurement requires an all solid state laser system with high energy, high efficiency and narrow linewidth that operates in the eye safe region. A Q-switched, diode pumped Ho:Tm:YLF 2 micrometer laser with output energy of as much as 125 mJ at 6 Hz with an optical-to-optical efficiency of 3% has been reported. Single frequency operation of the laser was achieved by injection seeding. The design of this laser is being incorporated into NASA's SPARCLE (SPAce Readiness Coherent Lidar Experiment) wind lidar mission. Laser output energy ranging from 500 mJ to 2 J is required for an operational space coherent lidar. We previously developed a high energy Ho:Tm:YLF master oscillator and side pumped power amplifier system and demonstrated a 600-mJ single frequency pulse at a repetition rate of 10 Hz. Although the output energy is high, the optical-to-optical efficiency is only about 2%. Designing a high energy, highly efficient, conductively cooled 2-micrometer laser remains a challenge. In this paper, the preliminary result of an end-pumped amplifier that has a potential to provide a factor 3 of improvement in the system efficiency is reported.

Yu, Jirong↗
DOE OSTI2023

Exploring the Role of Neutral 4-Amino-1,2,4-triazole in the Formation of Hexanuclear f-Element Hydrolysis Products

Our recent observations of an unexpected Ce(III) hydrolysis product from the reaction of 4-amino-1,2,4-triazole (4-NH 2 -1,2,4-Triaz) with CeCl 3 ·7H 2 O, [Ce 6 (μ 3 -O) 4 (μ 3 -OH) 2 (μ 3 -Cl) 2 (Cl) 6 (μ 2 -4-NH 2 -1,2,4-Triaz) 12 ]·7H 2 O, the first high-nuclearity lanthanide complex where all Ln atoms are connected pairwise through 12 N-donor ligands or 12 neutral bridging ligands of any type, prompted us to explore the utility of this ligand in trapping additional f-element examples. Reactions of LnCl 3 ·6H 2 O (Ln = Nd, Eu, Ho) with a large excess of 4-NH 2 -1,2,4-Triaz (20 equiv) and with the addition of small amounts of water to help solubilize the metal salts led to the isolation of the unique hydrolysis products [Nd 6 (μ 3 -OH) 8 Cl 6 (μ 2 -4-NH 2 -1,2,4-Triaz) 12 ][Cl 4 ]·2H 2 O, [Eu 6 (μ 6 -Cl) 0.23 (μ 3 -O 0.77 ) 4 (μ 3 -O) 2.6 (μ 3 -Cl) 0.4 Cl 6 (μ 2 -4-NH 2 -1,2,4-Triaz) 12 ], and [Ho 6 (μ 6 -Cl) 0.21 (μ 3 -O 0.79 ) 4 (μ 3 -OH) 2 Cl 6 (μ 2 -4-NH 2 -1,2,4-Triaz) 12 ][Cl] 3.4 . Here, we also report a Ce(III) analogue prepared in glassware contaminated with Pb(OAc) 2 , namely, [Ce 6 (μ 3 -OH) 8 (BrPbBr 5 )(μ 2 -4-NH 2 -1,2,4-Triaz) 11.5 (OH 2 ) 6 ][Pb 0.84 Br 4.2 ][Br] 3.8 ·2(4-NH 2 -1,2,4-Triaz)·3.6H 2 O. The Nd(III) complex is the structurally most ordered with a clear [Nd 6 (μ 3 -OH) 8 ] cluster core, while the Eu(III) and Ho(III) compounds contain partial occupancy of a μ 6 position and thus result in an incomplete Ln 6 O 9 cluster core formation. The crystallographic results suggest that the 4-NH 2 -1,2,4-Triaz ligand brings Ln(III) ions together, followed by the formation of an Ln 6 O 8 or Ln 6 O 9 core with whatever remaining anions or ligands can be incorporated. Given the complexity of the hydrolysis products of nuclear waste, we expect to continue to find a myriad of closely related complex structures of these types for the f-elements.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Materials Data on Ho20In40Rh19 by Materials Project

Ho20Rh19In40 crystallizes in the tetragonal P-4m2 space group. The structure is three-dimensional. there are five inequivalent Ho sites. In the first Ho site, Ho is bonded in a 4-coordinate geometry to four equivalent Rh and eight In atoms. All Ho–Rh bond lengths are 3.00 Å. There are four shorter (3.28 Å) and four longer (3.46 Å) Ho–In bond lengths. In the second Ho site, Ho is bonded in a 4-coordinate geometry to four Rh and eight In atoms. There are two shorter (3.02 Å) and two longer (3.05 Å) Ho–Rh bond lengths. There are two shorter (3.34 Å) and six longer (3.35 Å) Ho–In bond lengths. In the third Ho site, Ho is bonded in a 3-coordinate geometry to four Rh and ten In atoms. There are a spread of Ho–Rh bond distances ranging from 3.06–3.58 Å. There are a spread of Ho–In bond distances ranging from 3.18–3.73 Å. In the fourth Ho site, Ho is bonded in a 2-coordinate geometry to two equivalent Rh and five In atoms. Both Ho–Rh bond lengths are 2.90 Å. There are a spread of Ho–In bond distances ranging from 3.11–3.40 Å. In the fifth Ho site, Ho is bonded in a 2-coordinate geometry to two equivalent Rh and seven In atoms. Both Ho–Rh bond lengths are 2.93 Å. There are a spread of Ho–In bond distances ranging from 3.11–3.44 Å. There are six inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to five Ho and five In atoms. There are a spread of Rh–In bond distances ranging from 2.82–2.86 Å. In the second Rh site, Rh is bonded in a 10-coordinate geometry to three Ho and six In atoms. There are a spread of Rh–In bond distances ranging from 2.73–2.98 Å. In the third Rh site, Rh is bonded in a 8-coordinate geometry to eight In atoms. There are four shorter (2.72 Å) and four longer (2.88 Å) Rh–In bond lengths. In the fourth Rh site, Rh is bonded in a 8-coordinate geometry to eight In atoms. There are four shorter (2.74 Å) and four longer (2.88 Å) Rh–In bond lengths. In the fifth Rh site, Rh is bonded in a distorted hexagonal bipyramidal geometry to eight In atoms. There are four shorter (2.69 Å) and four longer (2.89 Å) Rh–In bond lengths. In the sixth Rh site, Rh is bonded in a 10-coordinate geometry to three Ho and six In atoms. There are a spread of Rh–In bond distances ranging from 2.73–2.97 Å. There are nine inequivalent In sites. In the first In site, In is bonded in a 2-coordinate geometry to two equivalent Ho, two Rh, and one In atom. The In–In bond length is 3.23 Å. In the second In site, In is bonded in a 3-coordinate geometry to two equivalent Ho, three Rh, and one In atom. The In–In bond length is 3.22 Å. In the third In site, In is bonded in a 3-coordinate geometry to four Ho and three Rh atoms. In the fourth In site, In is bonded in a 2-coordinate geometry to two equivalent Ho and two equivalent Rh atoms. In the fifth In site, In is bonded in a 11-coordinate geometry to four Ho, three Rh, and two equivalent In atoms. Both In–In bond lengths are 3.31 Å. In the sixth In site, In is bonded in a 3-coordinate geometry to six Ho and three Rh atoms. In the seventh In site, In is bonded in a 11-coordinate geometry to four Ho, three Rh, and two equivalent In atoms. Both In–In bond lengths are 3.31 Å. In the eighth In site, In is bonded in a 2-coordinate geometry to five Ho, three Rh, and five In atoms. Both In–In bond lengths are 3.25 Å. In the ninth In site, In is bonded in a 7-coordinate geometry to five Ho, three Rh, and five In atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Tocopherol controls D1 amino acid oxidation by oxygen radicals in Photosystem II

Photosystem II (PSII) is an intrinsic membrane protein complex that functions as a light-driven water:plastoquinone oxidoreductase in oxygenic photosynthesis. Electron transport in PSII is associated with formation of reactive oxygen species (ROS) responsible for oxidative modifications of PSII proteins. In this study, oxidative modifications of the D1 and D2 proteins by the superoxide anion (O 2 •- ) and the hydroxyl (HO•) radicals were studied in WT and a tocopherol cyclase (vte1) mutant, which is deficient in the lipid-soluble antioxidant α-tocopherol. In the absence of this antioxidant, high-resolution tandem mass spectrometry was used to identify oxidation of D1: 130 E to hydroxyglutamic acid by O 2 •- at the Pheo D1 site. Additionally, D1: 246 Y was modified to either tyrosine hydroperoxide or dihydroxyphenylalanine by O 2 •- and HO • , respectively, in the vicinity of the nonheme iron. We propose that α-tocopherol is localized near PheoD1 and the nonheme iron, with its chromanol head exposed to the lipid–water interface. This helps to prevent oxidative modification of the amino acid’s hydrogen that is bonded to PheoD1 and the nonheme iron (via bicarbonate), and thus protects electron transport in PSII from ROS damage.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Kinetics and selectivity of methane oxidation on an IrO 2 (110) film

Undercoordinated, bridging O-atoms (O br ) are highly active as H-acceptors in alkane dehydrogenation on IrO 2 (110) surfaces but transform to HO br groups that are inactive toward hydrocarbons. The low C–H activity and high stability of the HO br groups cause the kinetics and product selectivity during CH 4 oxidation on IrO 2 (110) to depend sensitively on the availability of O br atoms prior to the onset of product desorption. From temperature programmed reaction spectroscopy (TPRS) and kinetic simulations, we identified two O br -coverage regimes that distinguish the kinetics and product formation during CH 4 oxidation on IrO 2 (110). Under excess O br conditions, when the initial O br coverage is greater than that needed to oxidize all the CH 4 to CO 2 and HO br groups, complete CH 4 oxidation is dominant and produces CO 2 in a single TPRS peak between 450 and 500 K. However, under O br -limited conditions, nearly all the initial O br atoms are deactivated by conversion to HO br or abstracted after only a fraction of the initially adsorbed CH 4 oxidizes to CO 2 and CO below 500 K. Thereafter, some of the excess CH x groups abstract H and desorb as CH 4 above ~500 K while the remainder oxidize to CO 2 and CO at a rate that is controlled by the rate at which Obr atoms are regenerated from HObr during the formation of CH 4 and H 2 O products. We also show that chemisorbed O-atoms ('on-top O') on IrO 2 (110) enhance CO 2 production below 500 K by efficiently abstracting H from Obr atoms and thereby increasing the coverage of O br atoms available to completely oxidize CH x groups at low temperature. Furthermore, our results provide new insights for understanding factors which govern the kinetics and selectivity during CH 4 oxidation on IrO 2 (110) surfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

EXAFS investigation of the local structure in URu 2-x Fe x Si 2 : Evidence for distortions below 100 K

X-ray absorption measurements at the U L III , Ru K , and Fe K edges are reported for the hidden order (HO) material URu 2 - x Fe x Si 2 ( x = 0 , 0.05, 0.08, 0.10, 0.12, 0.15, and 0.20) as a function of x and temperature T . Furthermore, when Fe is substituted for Ru, the local structure about Fe shrinks slightly and the first neighbor Fe-Si bond length decreases by ≈ 0.05 Å . More importantly excess disorder is observed below 80–100 K (the coherence temperature T * ) in plots of the Debye-Waller factor σ 2 ( σ is the width of the pair distribution function); at low T the data deviate from the usual Einstein or correlated-Debye model plots. This excess disorder is most prominent for the Ru-Si bond, and σ 2 actually increases below 80 K. These results suggest a local orthorhombic distortion with B 1 g -like symmetry that develops below 80–100 K. A model that describes these local distortions is presented, and discussed in terms of other measurements that indicate a breaking of fourfold symmetry at low T . In addition, the square root of the difference between σ 2 ( T ) for the Ru-Si pair and a Debye fit to these data serves as an order parameter for this orthorhombic distortion, in the temperature range below 100 K. This quantity is a length related to a - b , the difference between the a and b lattice constants in the orthorhombic phase, and provides a connection between this distortion and T * . X-ray absorption near edge structure (XANES) measurements also show that there are no changes in the edge positions down to 0.1 eV for any edge as a function of x , for T in the HO regime.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Ho2Fe17C by Materials Project

Ho2Fe17C crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are four inequivalent Ho sites. In the first Ho site, Ho is bonded in a distorted bent 120 degrees geometry to twelve Fe and two equivalent C atoms. There are a spread of Ho–Fe bond distances ranging from 2.96–3.29 Å. Both Ho–C bond lengths are 2.49 Å. In the second Ho site, Ho is bonded in a 2-coordinate geometry to twenty Fe atoms. There are a spread of Ho–Fe bond distances ranging from 2.94–3.19 Å. In the third Ho site, Ho is bonded in a distorted bent 120 degrees geometry to ten Fe and two equivalent C atoms. There are a spread of Ho–Fe bond distances ranging from 2.96–3.38 Å. Both Ho–C bond lengths are 2.46 Å. In the fourth Ho site, Ho is bonded in a 12-coordinate geometry to eighteen Fe atoms. There are a spread of Ho–Fe bond distances ranging from 2.98–3.32 Å. There are fourteen inequivalent Fe sites. In the first Fe site, Fe is bonded to two Ho and ten Fe atoms to form FeHo2Fe10 cuboctahedra that share corners with ten FeHo2Fe10 cuboctahedra, a cornercorner with one CHo2Fe4 octahedra, edges with four FeHo3Fe9 cuboctahedra, faces with nine FeHo2Fe10 cuboctahedra, and a faceface with one CHo2Fe4 octahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of Fe–Fe bond distances ranging from 2.44–2.62 Å. In the second Fe site, Fe is bonded to two Ho and ten Fe atoms to form FeHo2Fe10 cuboctahedra that share corners with twelve FeHo2Fe10 cuboctahedra, edges with four FeHo3Fe9 cuboctahedra, faces with eight FeHo2Fe10 cuboctahedra, and faces with two equivalent CHo2Fe4 octahedra. There are a spread of Fe–Fe bond distances ranging from 2.44–2.64 Å. In the third Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.53–2.70 Å. The Fe–C bond length is 1.84 Å. In the fourth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.40–2.71 Å. The Fe–C bond length is 1.84 Å. In the fifth Fe site, Fe is bonded in a 12-coordinate geometry to two Ho and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.56–2.76 Å. In the sixth Fe site, Fe is bonded in a 12-coordinate geometry to two Ho and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.43–2.78 Å. In the seventh Fe site, Fe is bonded in a 12-coordinate geometry to two Ho and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.43–2.78 Å. In the eighth Fe site, Fe is bonded in a 12-coordinate geometry to two Ho and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.55–2.76 Å. In the ninth Fe site, Fe is bonded in a 2-coordinate geometry to one Ho and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.37–2.69 Å. In the tenth Fe site, Fe is bonded in a 2-coordinate geometry to one Ho and thirteen Fe atoms. There are one shorter (2.40 Å) and three longer (2.66 Å) Fe–Fe bond lengths. In the eleventh Fe site, Fe is bonded in a single-bond geometry to one Ho, seven Fe, and one C atom. There are one shorter (2.48 Å) and one longer (2.50 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.92 Å. In the twelfth Fe site, Fe is bonded to three Ho and nine Fe atoms to form distorted FeHo3Fe9 cuboctahedra that share corners with nine FeHo2Fe10 cuboctahedra, corners with four equivalent CHo2Fe4 octahedra, edges with eight FeHo2Fe10 cuboctahedra, and faces with six FeHo2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 66°. Both Fe–Fe bond lengths are 2.47 Å. In the thirteenth Fe site, Fe is bonded to three Ho and nine Fe atoms to form distorted FeHo3Fe9 cuboctahedra that share corners with eleven FeHo2Fe10 cuboctahedra, a cornercorner with one CHo2Fe4 octahedra, edges with five FeHo2Fe10 cuboctahedra, faces with nine FeHo2Fe10 cuboctahedra, and a faceface with one CHo2Fe4 octahedra. The corner-sharing octahedral tilt angles are 42°. In the fourteenth Fe site, Fe is bonded to three Ho and nine Fe atoms to form distorted FeHo3Fe9 cuboctahedra that share corners with fifteen FeHo2Fe10 cuboctahedra, edges with four FeHo2Fe10 cuboctahedra, faces with eight FeHo2Fe10 cuboctahedra, and faces with two equivalent CHo2Fe4 octahedra. C is bonded to two Ho and four Fe atoms to form CHo2Fe4 octahedra that share corners with eight FeHo2Fe10 cuboctahedra, corners with two equivalent CHo2Fe4 octahedra, and faces with eight FeHo3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 62°.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Chloride Insertion Enhances the Electrochemical Oxidation of Iron Hydroxide Double-Layer Hydroxide into Oxyhydroxide in Alkaline Iron Batteries

Rechargeable alkaline iron batteries that constitute environmentally benign electrolytes and earth-abundant industrial materials are desirable green solutions for large-scale energy storage. As one of the most abundant metal elements in the earth’s crust, iron (Fe) can satisfy nearly all criteria for low-cost and safe battery electrodes. However, challenges in achieving reversible Fe redox impede their extensive implementation in modern energy supply systems. Here, this study revealed that Cl-anion insertion into Fe(OH) 2 layered double hydroxide (LDH) formed a green rust intermediate phase with the formula [Fe 2 2+ Fe 1 3+ (HO – ) 6 ] + [Cl] – , which assisted a high Fe(OH) 2 /FeOOH conversion reaction (64.7%) and improved cycling stability. This new iron redox chemistry was validated by operando X-ray diffraction, electrochemical testing, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) analysis, scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS) mapping, and molecular dynamics (MD) simulations. Our study provides new insight into designing LDH materials for high-capacity alkaline iron batteries.

36 MATERIALS SCIENCE↗
NASA NTRS2017

Corrigendum to "New Approaches to Inferences for Steep-Sided Domes on Venus" [J. Volcanol. Geotherm. Res. 319 (2016) 93-105]

A typographical error contained in Quick et al. (2016) indicates the incorrect units for the value of the combined quantity (roh(exp. 3)o) that is the basis of Figs. 5, 6, and 7, and Tables 2 and 3. Using the values of ro and ho provided in Table 2, it can easily be shown that the combined quantity is correctly stated as roh(exp. 3)o =0.617 km(exp. 4). As correctly stated in Quick et al. (2016), the combined quantity of (roh(exp. 3)o) determines the family of curves shown in Fig. 5. The derivation of this relationship is shown below for completeness. Note that all results as reported in Quick et al. (2016) remained unchanged.

Quick, Lynnae C.↗
DOE OSTI2021

Role of Pr-Vacancies and O-Interstitials on the Activity and Stability of (Pr 1−x Ln x ) 2 NiO 4 (Ln = La, Nd, Pm, Sm, Gd, Tb, Dy, and Ho) towards Oxygen Reduction Reactions: A DFT Study

Praseodymium nickelate, Pr 2 NiO 4 (PNO), is a promising electrode to promote oxygen reduction reaction (ORR) in a solid oxide fuel cell, but it exhibits phase transformation during electrochemical operation. The origin of the simultaneous phase transformation and high electrochemical performance remains obscure. We carried out a systematic density functional theory study to elucidate the mechanism for this conjugated phenomenon. Charge, electronic structure, and normal-mode analysis suggest the presence of peroxide. Our study shows that the formation of peroxide (O 2 2– ) is attributed to both oxygen interstitials and Pr vacancies. The peroxide species limits the oxygen ion migration due to the additional energy required to break its O–O bond, which leads to a decrease in ORR activity. Subsequently, we investigate the diffusion paths of Pr-ions while comparing them with those of other Ln 3+ ions (La, Nd, Pm, Sm, Gd, Tb, Dy, and Ho) in PNO. The formation energies for various Ln 3+ cation occupancies are calculated, as well as segregation energies in CeO 2 (111) surfaces. Lastly, criteria for effective Ln 3+ dopants are developed. La, Nd, and Pm are proposed as potential substituents in PNO to obtain a stable structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗