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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NpGa5Ni by Materials Project

NpNiGa5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Np is bonded to twelve Ga atoms to form NpGa12 cuboctahedra that share corners with four equivalent NpGa12 cuboctahedra, faces with four equivalent NpGa12 cuboctahedra, and faces with four equivalent GaNp4Ga8 cuboctahedra. There are eight shorter (2.99 Å) and four longer (3.00 Å) Np–Ga bond lengths. Ni is bonded in a body-centered cubic geometry to eight Ga atoms. All Ni–Ga bond lengths are 2.51 Å. There are three inequivalent Ga sites. In the first Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Np, two equivalent Ni, and seven Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.66–3.00 Å. In the second Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Np, two equivalent Ni, and seven Ga atoms. There are two shorter (2.99 Å) and four longer (3.00 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded to four equivalent Np and eight Ga atoms to form distorted GaNp4Ga8 cuboctahedra that share corners with four equivalent GaNp4Ga8 cuboctahedra, faces with four equivalent NpGa12 cuboctahedra, and faces with four equivalent GaNp4Ga8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np2InPd2 by Materials Project

Np2Pd2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Np is bonded in a 6-coordinate geometry to six equivalent Pd and four equivalent In atoms. There are two shorter (2.87 Å) and four longer (3.02 Å) Np–Pd bond lengths. All Np–In bond lengths are 3.42 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Np, one Pd, and two equivalent In atoms. The Pd–Pd bond length is 2.82 Å. Both Pd–In bond lengths are 3.01 Å. In is bonded to eight equivalent Np and four equivalent Pd atoms to form a mixture of face and corner-sharing InNp8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NpGa4 by Materials Project

NpGa4 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Np is bonded in a 9-coordinate geometry to thirteen Ga atoms. There are a spread of Np–Ga bond distances ranging from 3.03–3.14 Å. There are three inequivalent Ga sites. In the first Ga site, Ga is bonded in a 10-coordinate geometry to three equivalent Np and seven Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.61–3.05 Å. In the second Ga site, Ga is bonded in a 12-coordinate geometry to four equivalent Np and eight Ga atoms. There are four shorter (3.06 Å) and two longer (3.14 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 3-coordinate geometry to three equivalent Np and ten Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3NpO10 by Materials Project

Na3NpO10 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded to six O atoms to form NaO6 octahedra that share corners with four equivalent NpO6 octahedra. The corner-sharing octahedra tilt angles range from 26–61°. There are a spread of Na–O bond distances ranging from 2.28–2.67 Å. In the second Na site, Na is bonded in a 2-coordinate geometry to six O atoms. There are a spread of Na–O bond distances ranging from 2.32–2.91 Å. Np is bonded to six O atoms to form NpO6 octahedra that share corners with four equivalent NaO6 octahedra. The corner-sharing octahedra tilt angles range from 26–61°. There are a spread of Np–O bond distances ranging from 1.88–2.45 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to one Na, one Np, and one O atom. The O–O bond length is 1.41 Å. In the second O site, O is bonded in a distorted bent 150 degrees geometry to two Na and one Np atom. In the third O site, O is bonded in a trigonal non-coplanar geometry to two Na and one Np atom. In the fourth O site, O is bonded in a distorted T-shaped geometry to two equivalent Na and one O atom. The O–O bond length is 1.34 Å. In the fifth O site, O is bonded in a see-saw-like geometry to two Na and two O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaSr2Np by Materials Project

BaSr2Np crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ba is bonded in a distorted body-centered cubic geometry to four equivalent Sr and four equivalent Np atoms. All Ba–Sr bond lengths are 3.99 Å. All Ba–Np bond lengths are 3.99 Å. There are two inequivalent Sr sites. In the first Sr site, Sr is bonded in a distorted body-centered cubic geometry to four equivalent Ba and four equivalent Sr atoms. All Sr–Sr bond lengths are 3.99 Å. In the second Sr site, Sr is bonded to four equivalent Sr and four equivalent Np atoms to form distorted edge-sharing SrSr4Np4 tetrahedra. All Sr–Np bond lengths are 3.99 Å. Np is bonded in a body-centered cubic geometry to four equivalent Ba and four equivalent Sr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3NpO8 by Materials Project

Na3NpO8 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.83 Å. In the second Na site, Na is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of Na–O bond distances ranging from 2.33–2.88 Å. Np is bonded in a distorted octahedral geometry to six O atoms. There are a spread of Np–O bond distances ranging from 1.90–2.44 Å. There are four inequivalent O sites. In the first O site, O is bonded in a distorted see-saw-like geometry to two Na, one Np, and one O atom. The O–O bond length is 1.35 Å. In the second O site, O is bonded to three Na and one Np atom to form a mixture of distorted edge and corner-sharing ONa3Np trigonal pyramids. In the third O site, O is bonded in a distorted rectangular see-saw-like geometry to three Na and one Np atom. In the fourth O site, O is bonded in a 4-coordinate geometry to three Na and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np2I2O by Materials Project

Np2OI2 is Cyanogen Chloride-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is zero-dimensional and consists of one Np2OI2 cluster. Np is bonded in a distorted linear geometry to one O and one I atom. The Np–O bond length is 2.06 Å. The Np–I bond length is 2.89 Å. O is bonded in a linear geometry to two equivalent Np atoms. I is bonded in a single-bond geometry to one Np atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np2Re3Si5 by Materials Project

Np2Re3Si5 crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. Np+3.50+ is bonded in a 9-coordinate geometry to nine Si4- atoms. There are a spread of Np–Si bond distances ranging from 2.89–3.22 Å. There are two inequivalent Re+4.33+ sites. In the first Re+4.33+ site, Re+4.33+ is bonded to six Si4- atoms to form a mixture of distorted edge, face, and corner-sharing ReSi6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Re–Si bond distances ranging from 2.46–2.54 Å. In the second Re+4.33+ site, Re+4.33+ is bonded in a distorted hexagonal planar geometry to six Si4- atoms. There are four shorter (2.48 Å) and two longer (2.72 Å) Re–Si bond lengths. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 9-coordinate geometry to three equivalent Np+3.50+, four Re+4.33+, and two equivalent Si4- atoms. Both Si–Si bond lengths are 2.61 Å. In the second Si4- site, Si4- is bonded in a 11-coordinate geometry to four equivalent Np+3.50+, three Re+4.33+, and four Si4- atoms. Both Si–Si bond lengths are 2.75 Å. In the third Si4- site, Si4- is bonded in a 9-coordinate geometry to four equivalent Np+3.50+, four equivalent Re+4.33+, and one Si4- atom. The Si–Si bond length is 2.53 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3Np by Materials Project

Na3Np is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded to eight Na and four equivalent Np atoms to form distorted NaNa8Np4 cuboctahedra that share corners with four equivalent NpNa12 cuboctahedra, corners with fourteen NaNa8Np4 cuboctahedra, edges with six equivalent NpNa12 cuboctahedra, edges with twelve NaNa8Np4 cuboctahedra, faces with four equivalent NpNa12 cuboctahedra, and faces with sixteen NaNa8Np4 cuboctahedra. There are a spread of Na–Na bond distances ranging from 3.53–3.83 Å. All Na–Np bond lengths are 3.68 Å. In the second Na site, Na is bonded to eight Na and four equivalent Np atoms to form distorted NaNa8Np4 cuboctahedra that share corners with four equivalent NpNa12 cuboctahedra, corners with fourteen NaNa8Np4 cuboctahedra, edges with six equivalent NpNa12 cuboctahedra, edges with twelve NaNa8Np4 cuboctahedra, faces with four equivalent NpNa12 cuboctahedra, and faces with sixteen NaNa8Np4 cuboctahedra. Both Na–Na bond lengths are 3.58 Å. All Na–Np bond lengths are 3.68 Å. Np is bonded to twelve Na atoms to form NpNa12 cuboctahedra that share corners with six equivalent NpNa12 cuboctahedra, corners with twelve NaNa8Np4 cuboctahedra, edges with eighteen NaNa8Np4 cuboctahedra, faces with eight equivalent NpNa12 cuboctahedra, and faces with twelve NaNa8Np4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NpSbPd2 by Materials Project

NpPd2Sb is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Np is bonded in a body-centered cubic geometry to eight equivalent Pd and six equivalent Sb atoms. All Np–Pd bond lengths are 2.93 Å. All Np–Sb bond lengths are 3.39 Å. Pd is bonded in a body-centered cubic geometry to four equivalent Np and four equivalent Sb atoms. All Pd–Sb bond lengths are 2.93 Å. Sb is bonded in a distorted body-centered cubic geometry to six equivalent Np and eight equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg16NpAl12 by Materials Project

Mg16NpAl12 crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to three equivalent Mg, one Np, and six equivalent Al atoms. All Mg–Mg bond lengths are 3.04 Å. The Mg–Np bond length is 3.24 Å. All Mg–Al bond lengths are 3.13 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five equivalent Al atoms. There are two shorter (3.07 Å) and four longer (3.15 Å) Mg–Mg bond lengths. There are a spread of Mg–Al bond distances ranging from 2.87–3.19 Å. Np is bonded in a 12-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Np–Al bond lengths are 3.16 Å. Al is bonded in a 11-coordinate geometry to seven Mg, one Np, and three equivalent Al atoms. There are one shorter (2.66 Å) and two longer (2.73 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3Np by Materials Project

Pu3Np is alpha La-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to eight Pu and four equivalent Np atoms to form PuPu8Np4 cuboctahedra that share corners with twelve equivalent PuPu8Np4 cuboctahedra, edges with eight equivalent NpPu12 cuboctahedra, edges with sixteen PuPu8Np4 cuboctahedra, faces with four equivalent NpPu12 cuboctahedra, and faces with fourteen PuPu8Np4 cuboctahedra. There are four shorter (3.18 Å) and four longer (3.20 Å) Pu–Pu bond lengths. All Pu–Np bond lengths are 3.18 Å. In the second Pu site, Pu is bonded to eight equivalent Pu and four equivalent Np atoms to form PuPu8Np4 cuboctahedra that share corners with four equivalent PuPu8Np4 cuboctahedra, corners with eight equivalent NpPu12 cuboctahedra, edges with twenty-four PuPu8Np4 cuboctahedra, faces with six equivalent NpPu12 cuboctahedra, and faces with twelve PuPu8Np4 cuboctahedra. All Pu–Np bond lengths are 3.20 Å. Np is bonded to twelve Pu atoms to form NpPu12 cuboctahedra that share corners with four equivalent NpPu12 cuboctahedra, corners with eight equivalent PuPu8Np4 cuboctahedra, edges with eight equivalent NpPu12 cuboctahedra, edges with sixteen equivalent PuPu8Np4 cuboctahedra, faces with four equivalent NpPu12 cuboctahedra, and faces with fourteen PuPu8Np4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Using Aggregation to Chaperone Nanoparticles Across Fluid Interfaces

Abstract Nanoparticles (NPs) transfer is usually induced by adding ligands to modify NP surfaces, but aggregation of NPs oftentimes hampers the transfer. Here, we show that aggregation during NP phase transfer does not necessarily result in transfer failure. Using a model system comprising gold NPs and amphiphilic polymers, we demonstrate an unusual mechanism by which NPs can undergo phase transfer from the aqueous phase to the organic phase via a single‐aggregation‐single pathway. Our discovery challenges the conventional idea that aggregation inhibits NP transfer and provides an unexpected pathway for transferring larger‐sized NPs (>20 nm). The charged amphiphilic polymers effectively act as chaperons for the NP transfer and offer a unique way to manipulate the dispersion and distribution of NPs in two immiscible liquids. Moreover, by intentionally jamming the NP‐polymer assembly at the liquid/liquid interface, the transfer process can be inhibited.

Fu, Yuchen↗
DOE OSTI2023

Using Aggregation to Chaperone Nanoparticles Across Fluid Interfaces

Nanoparticles (NPs) transfer is usually induced by adding ligands to modify NP surfaces, but aggregation of NPs oftentimes hampers the transfer. Here, we show that aggregation during NP phase transfer does not necessarily result in transfer failure. Using a model system comprising gold NPs and amphiphilic polymers, we demonstrate an unusual mechanism by which NPs can undergo phase transfer from the aqueous phase to the organic phase via a single-aggregation-single pathway. Our discovery challenges the conventional idea that aggregation inhibits NP transfer and provides an unexpected pathway for transferring larger-sized NPs (>20 nm). The charged amphiphilic polymers effectively act as chaperons for the NP transfer and offer a unique way to manipulate the dispersion and distribution of NPs in two immiscible liquids. Moreover, by intentionally jamming the NP-polymer assembly at the liquid/liquid interface, the transfer process can be inhibited.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Insights into the Mechanism of Neptunium Oxidation to the Heptavalent State

Abstract Neptunium can exist in multiple oxidation states, including the rare and poorly understood heptavalent form. In this work, we monitored the formation of heptavalent neptunium [Np(VII)O 4 (OH) 2 ] 3− during ozonolysis of aqueous M OH ( M =Li, Na, K) solutions using a combined experimental and theoretical approach. All experimental reactions were closely monitored via absorption and vibrational spectroscopy to follow both the oxidation state and the speciation of neptunium guided by the calculated vibrational frequencies for various neptunium species. The mechanism of the reaction partly involves oxidative dissolution of transient Np(VI) oxide/hydroxide solid phases, the identity of which are dependent on the co‐precipitating counter‐cation Li + /Na + /K + . Additional calculations suggest that the most favorable energetic pathway occurs through the reaction of a [Np(V)O 2 (OH) 4 ] 3− with the hydroxide radical to form [Np(VI)O 2 (OH) 4 ] 2− , followed by an additional oxidation with HO⋅ to create [Np(VII)O 4 (OH) 2 ] 3− .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Density Functional Theory Guided Investigation of Ligand‐Induced Neptunyl‐Neptunyl Interactions

Abstract Actinyl‐actinyl interactions are particularly prevalent for the pentavalent neptunyl cation (Np(V)O 2 ) + where these interactions appear either as a T ‐ or D ‐shape (diamond‐shape). T ‐shaped interactions have been previously identified in high concentration Np(V) solutions containing simple anions (NO 3 − , ClO 4 − , Cl − ) whereas D ‐shaped have only been isolated in the solid‐state in the presence of carboxylate ligands. In this study, Density Functional Theory (DFT) calculations were paired with Raman spectroscopy to evaluate the formation of D ‐shaped interactions in the presence of aliphatic (R=H (formate), CH 3 (acetate), CH 2 CH 3 (propionate)) and aromatic (R=C 6 H 5 (benzoate), C 6 H 4 OH (4‐hydroxybenzoate), C 5 H 4 N (isonicotinate)) carboxylate ligands. DFT studies indicate that the Δ G to form hydrated T ‐ and D ‐shaped forms are not spontaneous but become so with the addition of the carboxylate ligands. Raman spectra of the Np(V) carboxylate solutions contained vibrational modes associated with the D ‐shaped interactions, but spectral changes observed over time indicate a dynamic system. Crystallization experiments from the Np(V) carboxylate systems confirmed the presence of D‐ shaped dimers for the aromatic carboxylates, suggesting that the choice of the anion in solution favors actinyl‐actinyl interactions even at low concentrations (≤20 mM) of Np(V).

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

Future Trends in Nuclear Physics Computing

In nuclear physics (NP) today the study of quarks, gluons and their strong interactions extends across a broad research program at a varied range of collaborative scales, from a few collaborators up to large experiments at scales comparable to those typical of high energy physics (HEP). Overall, the software and computing efforts vary accordingly, from pragmatic do-it-yourself approaches among a few, to substantial organized software and computing activities within large experiments. With new experiments starting up and on the horizon [1], and rapidly increasing data volumes [2, 3] and processing demands even at small experiments, the NP community has in recent years been thinking about the next generation of data processing and analysis workflows that will maximize the science output. One context for this discussion has been a series of workshops, “Future Trends in Nuclear Physics Computing” [4]. The most recent in this series took place in Fall 2020, organized by the authors together with colleagues. The workshop focused on identifying the unique aspects of software and computing in NP, and discussing how the NP community could strengthen common efforts and chart a path forward for the next decade, sure to be an exciting one with rich ongoing scientific programs at Brookhaven National Laboratory (BNL), Jefferson Lab (JLab), and other NP facilities, and culminating in datataking at the Electron-Ion Collider (EIC) [5,6,7] in the early 2030s. Without claiming to present a collective view from the workshop and discussions since—fortunately this is not expected of us in this opinion editorial—we offer here our reflections on the topic, informed by the workshop and the summary we authored with our colleagues [8], as well as discussions and developments in the eventful time since.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Building Durable Multimetallic Electrocatalysts from Intermetallic Seeds

When combined with earth-abundant metals, Pt-based alloy nanoparticles (NPs) can be cost-effective electrocatalysts. However, these NPs can experience leaching of non-noble-metal components under harsh electrocatalytic conditions. In this work, the Skrabalak group has demonstrated a novel NP construct in which Pt-based random alloy surfaces are stabilized against non-noble-metal leaching by their deposition onto intermetallic seeds. These core@shell NPs are highly durable electrocatalysts, with the ability to tune catalytic performance by the core@shell architecture, surface alloy composition, and NP shape. This versatility was demonstrated in a model system in which random alloy (ra-) PtM surfaces were deposited onto ordered intermetallic (i-) PdCu seeds using seed-mediated co-reduction (SMCR). In the initial demonstration, ra-PtCu shells were deposited on i-PdCu seeds, with these core@shell NPs exhibiting higher specific and mass activities for the oxygen reduction reaction (ORR) when compared to similarly sized ra-PtCu NPs. These NPs also showed outstanding durability, maintaining ~85% in specific activity after 5000 cycles. Characterization of the NPs after use revealed minimal loss of Cu. The activity enhancement was attributed to the strained surface that arises from the lattice mismatch between the intermetallic core and random alloy surface. The outstanding durability was attributed to the ordered structure of the intermetallic core. The origin of this durability enhancement was investigated by classical molecular dynamics simulations, where Pt atoms were found to have a lower potential energy when deposited on an intermetallic core than when deposited on a random alloy core. Also, ordering of Cu atoms at the core@shell interface appears to enhance the overall binding between the core and the shell materials. Inspired by this initial demonstration, SMCR has been used to achieve shells of different random alloy compositions, PtM (M = Ni, Co, Cu, or Fe). This advance is significant because ligand effects vary as a function of PtM identity and Pt/M ratio. These features also influence the degree of surface strain imparted from the lattice mismatch between the core and shell materials. Like the initial demonstration, standout features of these core@shell NPs were high durability and resistance to non-noble metal leaching. Moving forward, efforts have been directed toward integrating shape-control to this core@shell NP construct. This integration is motivated by the shape-dependent catalytic performance of NPs derived from the selective expression of specific facets. Considering the initial i-PdCu@ra-PtCu system, NPs with a cubic shape have been achieved by judicious selection of capping ligands during SMCR. Evaluation of these NPs as catalysts for the electrooxidation of formic acid found that the nanocubic shape enhances catalytic performance compared to similar core@shell NPs with a spherical morphology. We envision that SMCR can be applied to other NP systems to achieve highly durable catalysts as the syntheses of monodisperse and shape-controlled intermetallic seeds are advanced. This Account highlights the role of intermetallic cores in providing more durable electrocatalysts. More broadly, the versatility of SMCR is highlighted as a route to integrate architecture, alloy surfaces, and shape within one NP system, and how this achievement is inspiring new high-performance and robust catalysts is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗