Vibrational and electronic properties of NpO from experimental spectroscopy and first principles calculations

Binod K. Rai; Shuxiang Zhou; Benjamin R. Heiner; Gia Thinh Tran; Jennifer E.S. Szymanowski; Santosh KC; Thomas C. Shehee; Peter C. Burns; Miles F. Beaux; Luke R. Sadergaski

doi:10.1038/s41598-026-36720-x

Vibrational and electronic properties of NpO from experimental spectroscopy and first principles calculations

Binod K. Rai
, Shuxiang Zhou
, Benjamin R. Heiner
, Gia Thinh Tran
, Jennifer E.S. Szymanowski
, Santosh KC
, Thomas C. Shehee
, Peter C. Burns
, Miles F. Beaux
, Luke R. Sadergaski

Radiochemical Process Development

Research output: Contribution to journal › Article › peer-review

Abstract

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 NpO 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 NpO, and opening new avenues for probing structure–property relationships in complex f-electron materials.

Original language	English
Article number	10883
Journal	Scientific Reports
Volume	16
Issue number	1
DOIs	https://doi.org/10.1038/s41598-026-36720-x
State	Published - Dec 2026

Funding

This work was supported by the Laboratory Directed Research and Development program within the Savannah River National Laboratory. This work was produced by Battelle Savannah River Alliance, LLC under Contract No. 89303321CEM000080 with the U.S. Department of Energy. Publisher acknowledges the U.S. Government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan ). Work at INL was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. Work at LANL was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry Program under Early Career FWP No. EC2021LANL05. BRH was additionally supported by the G.T. Seaborg Institute for Transactinium Science. This work was supported by the Laboratory Directed Research and Development program within the Savannah River National Laboratory. This work was produced by Battelle Savannah River Alliance, LLC under Contract No. 89303321CEM000080 with the U.S. Department of Energy. Publisher acknowledges the U.S. Government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). Work at INL was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. Work at LANL was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry Program under Early Career FWP No. EC2021LANL05. BRH was additionally supported by the G.T. Seaborg Institute for Transactinium Science.

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@article{d8387b8b30644ad8bf633745dc5636af,

title = "Vibrational and electronic properties of NpO from experimental spectroscopy and first principles calculations",

abstract = "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 NpO 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 NpO, and opening new avenues for probing structure–property relationships in complex f-electron materials.",

author = "Rai, \{Binod K.\} and Shuxiang Zhou and Heiner, \{Benjamin R.\} and Tran, \{Gia Thinh\} and Szymanowski, \{Jennifer E.S.\} and Santosh KC and Shehee, \{Thomas C.\} and Burns, \{Peter C.\} and Beaux, \{Miles F.\} and Sadergaski, \{Luke R.\}",

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doi = "10.1038/s41598-026-36720-x",

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AU - Rai, Binod K.

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AU - Szymanowski, Jennifer E.S.

AU - KC, Santosh

AU - Shehee, Thomas C.

AU - Burns, Peter C.

AU - Beaux, Miles F.

AU - Sadergaski, Luke R.

N1 - Publisher Copyright: © Battelle Savannah River Alliance, LLC, Triad National Security, LLC, UT-Battelle, LLC, Idaho National Laboratory and Jennifer E. S. Szymanowski, Peter C. Burns, Santosh KC 2026.

PY - 2026/12

Y1 - 2026/12

N2 - 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 NpO 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 NpO, and opening new avenues for probing structure–property relationships in complex f-electron materials.

AB - 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 NpO 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 NpO, and opening new avenues for probing structure–property relationships in complex f-electron materials.

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Vibrational and electronic properties of NpO from experimental spectroscopy and first principles calculations

Abstract

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