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Results for “Np(OF)2”

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

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Improving understanding of NpO 2 and Np 2 O 5 through vibrational spectroscopy

Raman spectra of three NpO 2 samples and two samples produced from a modified direct denitration (MDD) process were collected. The spectral features of the NpO 2 samples were consistent and indicated only NpO 2 . The spectra of the MDD samples indicated the presence of NpO 2 and an additional phase attributed to the neptunium binary oxide Np 2 O 5 . These Raman spectra are the first reported of Np 2 O 5 , and the proportions of these neptunium oxide phases varied within the samples, suggesting significant sample inhomogeneity. Peaks in the Raman spectra of Np 2 O 5 at 569 and 782 cm –1 were tentatively assigned to concerted, symmetric stretches of the neptunyl cations. Finally, laser-induced heating of regions in the MDD samples that were rich in Np 2 O 5 showed spectral features that indicated conversion to NpO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Thermal decomposition of neptunyl ammonium nitrate: mechanistic insights and structural characterization of the Np 2 O 5 intermediate phase

Neptunium (Np) possesses a rich and unique chemistry that often diverges from other actinide elements yet remains relatively underexplored compared with the other light actinides. A resurgence of interest in Np has been spurred by the application of 237 Np for plutonium-238 ( 238 Pu) production for use in radioisotope thermoelectric generators (RTGs), necessitating evaluation of Np chemical reactions and materials. The work presented here studied the thermal decomposition of neptunyl ammonium nitrate (NH 4 Np VI O 2 (NO 3 ) 3 ) for synthesis of neptunium dioxide (NpO 2 ), which is the target material used for production of 238 Pu. Additionally, structural characterization of the intermediate solid Np pentoxide (Np 2 O 5 ) was performed. Advanced solid-state characterization techniques, including simultaneous thermal analysis (STA), powder X-ray diffraction (pXRD), Raman spectroscopy, and density functional theory (DFT) modeling have been combined to study the reaction pathways. Analysis revealed that NH 4 Np VI O 2 (NO 3 ) 3 thermally decomposes to a proposed neptunyl nitrate intermediate, followed by Np 2 O 5 and finally NpO 2 , all within the temperature range of 150 °C–600 °C. Further characterization of the pentoxide intermediate provided the first Raman spectra of pure-phase Np 2 O 5 and associated DFT modeling confirmed Raman peak assignments for this phase. These findings provide mechanistic information to advance production of the critical radioisotope 238 Pu and advance the state of knowledge on Np materials chemistry using modern characterization techniques.

Lawson, Kathryn M. [Oak Ridge National Laboratory ↗
DOE OSTI2026

Vibrational and electronic properties of Np 2 O 5 from experimental spectroscopy and first principles calculations

High-valence actinide oxides are critical to understanding the behavior of 5f-electrons, yet their structural and electronic properties remain poorly understood due to challenges in synthesis and handling. We report the first Raman spectroscopic study of single-crystalline Np 2 O 5 and the first scanning tunneling spectroscopy (STS) measurement on any neptunium-containing material. Hydrothermally synthesized crystals were structurally verified by X-ray diffraction. Raman spectra revealed sharply resolved vibrational features, including previously unreported low-frequency modes. STS measurements revealed a band gap of 1.5 eV. Density functional theory (DFT) enables vibrational mode assignments, reveals neptunium-dominated low-frequency phonons, oxygen-dominated high-frequency modes, and predicts an indirect band gap of 1.68 eV. This predicted value is in excellent agreement with the experimentally measured STS gap. This combined Raman, DFT, and STS approach provides a robust framework for correlating lattice dynamics and electronic structure in actinide materials, providing benchmark data for Np 2 O 5 , and opening new avenues for probing structure–property relationships in complex f-electron materials.

36 - MATERIALS SCIENCE↗
DOE OSTI2024

One-Pot Self-Assembly of Sequence-Controlled Mesoporous Heterostructures via Structure-Directing Agents

Multimaterial heterostructures have led to characteristics surpassing the individual components. Nature controls the architecture and placement of multiple materials through biomineralization of nanoparticles (NPs); however, synthetic heterostructure formation remains limited and generally departs from the elegance of self-assembly. Here, in this study, a class of block polymer structure-directing agents (SDAs) are developed containing repeat units capable of persistent (covalent) NP interactions that enable the direct fabrication of nanoscale porous heterostructures, where a single material is localized at the pore surface as a continuous layer. This SDA binding motif (design rule 1) enables sequence-controlled heterostructures, where the composition profile and interfaces correspond to the synthetic addition order. This approach is generalized with 5 material sequences using an SDA with only persistent SDA-NP interactions (“P-NP 1 –NP 2 ”; NP i = TiO 2 , Nb 2 O 5 , ZrO 2 ). Expanding these polymer SDA design guidelines, it is shown that the combination of both persistent and dynamic (noncovalent) SDA-NP interactions (“PD-NP 1 –NP 2 ”) improves the production of uniform interconnected porosity (design rule 2). The resulting competitive binding between two segments of the SDA (P- vs D-) requires additional time for the first NP type (NP 1 ) to reach and covalently attach to the SDA (design rule 3). The combination of these three design rules enables the direct self-assembly of heterostructures that localize a single material at the pore surface while preserving continuous porosity.

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

Laser spectroscopy of indium Rydberg atom bunches by electric field ionization

This work reports on the application of a novel electric field-ionization setup for high-resolution laser spectroscopy measurements on bunched fast atomic beams in a collinear geometry. In combination with multi-step resonant excitation to Rydberg states using pulsed lasers, the field ionization technique demonstrates increased sensitivity for isotope separation and measurement of atomic parameters over previous non-resonant laser ionization methods. The setup was tested at the Collinear Resonance Ionization Spectroscopy experiment at ISOLDE-CERN to perform high-resolution measurements of transitions in the indium atom from the 5s 2 5d 2 D 5/2 and 5s 2 5d 2 D 3/2 states to 5s 2 np 2 P and 5s 2 nf 2 F Rydberg states, up to a principal quantum number of n=72 . The extracted Rydberg level energies were used to re-evaluate the ionization potential of the indium atom to be 46,670.107(4)cm -1 . The nuclear magnetic dipole and nuclear electric quadrupole hyperfine structure constants and level isotope shifts of the 5s 2 5d 2 D 5/2 and 5s 2 5d 2 D 3/2 states were determined for 113,115 In. The results are compared to calculations using relativistic coupled-cluster theory. A good agreement is found with the ionization potential and isotope shifts, while disagreement of hyperfine structure constants indicates an increased importance of electron correlations in these excited atomic states. With the aim of further increasing the detection sensitivity for measurements on exotic isotopes, a systematic study of the field-ionization arrangement implemented in the work was performed at the same time and an improved design was simulated and is presented. The improved design offers increased background suppression independent of the distance from field ionization to ion detection.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Acceptance dependence of factorial cumulants, long-range correlations, and the antiproton puzzle

We analyze joint factorial cumulants of protons and antiprotons in relativistic heavy-ion collisions and point out that they obey the scaling Ĉnmp,p¯∝〈Np〉n〈Np¯〉m as a function of acceptance when only long-range correlations are present in the system, such as global baryon conservation and volume fluctuations. This hypothesis can be directly tested experimentally without the need for corrections for volume fluctuations. We show that if correlations among protons and antiprotons are driven by global baryon conservation and volume fluctuations only, the equality Ĉ2p/〈Np〉2=Ĉ2p¯/〈Np¯〉2 holds for large systems created in central collisions. We point out that the experimental data of the STAR Collaboration from phase I of the Relativistic Heavy Ion Collider (RHIC) beam energy scan (BES) are approximately consistent with the scaling Ĉnmp,p¯∝〈Np〉n〈Np¯〉m, but the normalized antiproton correlations are stronger than those of protons, −Ĉ2p¯/〈Np¯〉2>−Ĉ2p/〈Np〉2. Existing theoretical baselines, based on global baryon conservation and volume fluctuations, cannot explain the data, which we refer to as the antiproton puzzle. We also discuss high-order factorial cumulants which can be measured with sufficient precision within phase II of RHIC-BES.

Bzdak, Adam↗
DOE OSTI2020

Materials Data on Np(SO6)2 by Materials Project

Np(SO6)2 is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four Np(SO6)2 clusters. Np is bonded in a 4-coordinate geometry to six O atoms. There are a spread of Np–O bond distances ranging from 1.77–2.43 Å. S is bonded in a tetrahedral geometry to four O atoms. There are a spread of S–O bond distances ranging from 1.47–1.51 Å. There are seven inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a single-bond geometry to one Np atom. In the third O site, O is bonded in a single-bond geometry to one S atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Np and one S atom. In the fifth O site, O is bonded in a single-bond geometry to one Np atom. In the sixth O site, O is bonded in a single-bond geometry to one Np atom. In the seventh O site, O is bonded in a single-bond geometry to one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(OF)2 by Materials Project

Np(OF)2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Np(OF)2 sheets oriented in the (1, 0, 0) direction. Np6+ is bonded to four equivalent O2- and four equivalent F1- atoms to form edge-sharing NpO4F4 hexagonal bipyramids. All Np–O bond lengths are 2.32 Å. There are two shorter (2.23 Å) and two longer (2.37 Å) Np–F bond lengths. O2- is bonded in a 7-coordinate geometry to two equivalent Np6+ and one O2- atom. The O–O bond length is 1.48 Å. F1- is bonded in a distorted water-like geometry to two equivalent Np6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(OF)2 by Materials Project

Np(OF)2 crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three Np(OF)2 sheets oriented in the (0, 0, 1) direction. Np6+ is bonded to two equivalent O2- and six equivalent F1- atoms to form distorted edge-sharing NpO2F6 hexagonal bipyramids. Both Np–O bond lengths are 1.77 Å. All Np–F bond lengths are 2.44 Å. O2- is bonded in a single-bond geometry to one Np6+ atom. F1- is bonded in a trigonal planar geometry to three equivalent Np6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SiRh)2 by Materials Project

Np(RhSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Si atoms. All Np–Rh bond lengths are 3.22 Å. All Np–Si bond lengths are 3.05 Å. Rh is bonded to four equivalent Np and four equivalent Si atoms to form a mixture of distorted edge, corner, and face-sharing RhNp4Si4 tetrahedra. All Rh–Si bond lengths are 2.41 Å. Si is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Rh, and one Si atom. The Si–Si bond length is 2.34 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SiOs)2 by Materials Project

Np(OsSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np4+ is bonded in a 8-coordinate geometry to eight equivalent Os2- atoms. All Np–Os bond lengths are 3.17 Å. Os2- is bonded in a 4-coordinate geometry to four equivalent Np4+ and four equivalent Si atoms. All Os–Si bond lengths are 2.40 Å. Si is bonded in a 5-coordinate geometry to four equivalent Os2- and one Si atom. The Si–Si bond length is 2.35 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(WO4)2 by Materials Project

Np(WO4)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Np4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Np–O bond distances ranging from 2.30–2.41 Å. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of W–O bond distances ranging from 1.81–1.84 Å. In the second W6+ site, W6+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.81 Å) and two longer (1.82 Å) W–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one W6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one W6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one W6+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to one Np4+ and one W6+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Np4+ and one W6+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one W6+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one W6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one W6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SeO3)2 by Materials Project

Np(SeO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Np4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Np–O bond distances ranging from 2.25–2.58 Å. There are two inequivalent Se4+ sites. In the first Se4+ site, Se4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of Se–O bond distances ranging from 1.73–1.75 Å. In the second Se4+ site, Se4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of Se–O bond distances ranging from 1.71–1.77 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Np4+ and one Se4+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Np4+ and one Se4+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Np4+ and one Se4+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Np4+ and one Se4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Np4+ and one Se4+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Np4+ and one Se4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SiPt)2 by Materials Project

Np(PtSi)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Np4+ is bonded in a 8-coordinate geometry to eight Pt2- atoms. There are four shorter (3.22 Å) and four longer (3.28 Å) Np–Pt bond lengths. There are two inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded in a 5-coordinate geometry to four equivalent Np4+ and five Si atoms. There are one shorter (2.40 Å) and four longer (2.43 Å) Pt–Si bond lengths. In the second Pt2- site, Pt2- is bonded to four equivalent Np4+ and four equivalent Si atoms to form a mixture of distorted edge and face-sharing PtNp4Si4 tetrahedra. All Pt–Si bond lengths are 2.50 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 5-coordinate geometry to five Pt2- atoms. In the second Si site, Si is bonded to four equivalent Pt2- atoms to form a mixture of edge and corner-sharing SiPt4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(SiPd)2 by Materials Project

Np(PdSi)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np4+ is bonded to eight equivalent Si4- atoms to form NpSi8 hexagonal bipyramids that share corners with sixteen equivalent PdSi4 tetrahedra, edges with four equivalent NpSi8 hexagonal bipyramids, edges with eight equivalent PdSi4 tetrahedra, and faces with four equivalent NpSi8 hexagonal bipyramids. All Np–Si bond lengths are 3.11 Å. Pd2+ is bonded to four equivalent Si4- atoms to form PdSi4 tetrahedra that share corners with eight equivalent NpSi8 hexagonal bipyramids, corners with four equivalent PdSi4 tetrahedra, edges with four equivalent NpSi8 hexagonal bipyramids, and edges with four equivalent PdSi4 tetrahedra. All Pd–Si bond lengths are 2.49 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Np4+, four equivalent Pd2+, and one Si4- atom. The Si–Si bond length is 2.32 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(GePd)2 by Materials Project

Np(PdGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Ge atoms. All Np–Pd bond lengths are 3.38 Å. All Np–Ge bond lengths are 3.21 Å. Pd is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing PdNp4Ge4 tetrahedra. All Pd–Ge bond lengths are 2.53 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Pd, and one Ge atom. The Ge–Ge bond length is 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np(GeRh)2 by Materials Project

Np(RhGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Np is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Ge atoms. All Np–Rh bond lengths are 3.35 Å. All Np–Ge bond lengths are 3.18 Å. Rh is bonded to four equivalent Np and four equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing RhNp4Ge4 tetrahedra. All Rh–Ge bond lengths are 2.47 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Np, four equivalent Rh, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗