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DOE OSTI2023

Tunable Van Hove Singularity without Structural Instability in Kagome Metal $CsTi_{3}Bi_{5}$

In kagome metal $CsV_{3}Sb_{5}$, multiple intertwined orders are accompanied by both electronic and structural instabilities. These exotic orders have attracted much recent attention, but their origins remain elusive. The newly discovered $CsTi_{3}Bi_{5}$ is a Ti-based kagome metal to parallel $CsV_{3}Sb_{5}$. Here, in this work, we report angle-resolved photoemission experiments and first-principles calculations on pristine and Cs-doped $CsTi_{3}Bi_{5}$ samples. Our results reveal that the van Hove singularity (vHS) in $CsTi_{3}Bi_{5}$ can be tuned in a large energy range without structural instability, different from that in $CsV_{3}Sb_{5}$. As such, $CsTi_{3}Bi_{5}$ provides a complementary platform to disentangle and investigate the electronic instability with a tunable vHS in kagome metals.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Facile integration of giant exchange bias in Fe 5 Ge Te 2 / oxide heterostructures by atomic layer deposition

Exchange bias arises from the interfacial exchange coupling in ferromagnet-antiferromagnet bilayers and manifests as a horizontal shift of the magnetic hysteresis loop, constituting a critical component underpinning a broad range of magnetoresistive logic and memory devices. The facile implementation of exchange bias in van der Waals (vdW) magnets would be a key step towards practical devices for emerging vdW spintronics. Here, in this paper, we report an easy approach to establishing strong exchange bias in the vdW magnet Fe 5 GeTe 2 by a single-step process—atomic layer deposition (ALD) of oxides on Fe 5 GeTe 2 . We successfully created exchange bias of 300–1500 Oe in Fe 5 GeTe 2 /Al 2 O 3 , Fe 5 GeTe 2 /ZnO, and Fe 5 GeTe 2 /V 2 O 5 heterostructures, at 130 K. Control experiments showed that increasing the oxidant pulse duration in each ALD cycle or utilizing the stronger oxidant O 3 can enhance the exchange bias strength, revealing the key role of the ALD oxidants. Our systematic work elucidates the essential role of ALD-enabled oxidization of Fe 5 GeTe 2 in the formation of exchange bias, and establishes ALD of oxides as a facile, controllable, and generally effective approach to creating giant exchange bias in vdW magnets, representing an integral advance towards practical vdW spintronic devices.

36 MATERIALS SCIENCE↗

DOE OSTI2023

SFWST Disposal Research R&D 5-Year Plan (FY2023 Update)

This FY2023 report is the second update to the Disposal Research (DR) Research and Development (R&D) 5-year plan for the Spent Fuel and Waste Science and Technology (SFWST) Campaign DR R&D activities. In the planning for FY2020 in the U.S. Department of Energy (DOE) NE-81 SFWST Campaign, the DOE requested development of a high-level summary plan for activities in the DR R&D program for the next five (5)-year period, with periodic updates to this summary plan. The DR R&D 5-year plan was provided to the DOE based initially on the FY2020 priorities and program structure (initial 2020 version of this 5-year plan) and provides a strategic summary guide to the work within the DR R&D technical areas (Control Accounts, CA), focusing on the highest priority technical thrusts. This 5-year plan is a living document (planned to be updated periodically) that provides review of SFWST R&D accomplishments (as seen on the 2021 revision of this 5-year plan), describes changes to technical R&D prioritization based on (a) progress in each technical area (including external technical understanding) with specific accomplishments and (b) any changes in SFWST Campaign objectives and/or funding levels (i.e., Program Direction). Updates to this 5-year plan include the DR R&D adjustments to high-priority knowledge gaps to be investigated in the near-term, as well as the updated longer-term DR R&D directions for the program activities. This plan fulfills the Milestone M2SF23SN010304083 in DR Work Package (WP) SF-23SN01030408 (GDSA - Framework Development – SNL).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2022

Structural mechanism of allosteric activation of TRPML1 by PI(3,5)P 2 and rapamycin

Transient receptor potential mucolipin 1 (TRPML1) is a Ca 2+ -permeable, nonselective cation channel ubiquitously expressed in the endolysosomes of mammalian cells and its loss-of-function mutations are the direct cause of type IV mucolipidosis (MLIV), an autosomal recessive lysosomal storage disease. TRPML1 is a ligand-gated channel that can be activated by phosphatidylinositol 3,5-bisphosphate [PI(3,5)P 2 ] as well as some synthetic small-molecule agonists. Recently, rapamycin has also been shown to directly bind and activate TRPML1. Interestingly, both PI(3,5)P 2 and rapamycin have low efficacy in channel activation individually but together they work cooperatively and activate the channel with high potency. To reveal the structural basis underlying the synergistic activation of TRPML1 by PI(3,5)P 2 and rapamycin, we determined the high-resolution cryoelectron microscopy (cryo-EM) structures of the mouse TRPML1 channel in various states, including apo closed, PI(3,5)P 2 -bound closed, and PI(3,5)P 2 /temsirolimus (a rapamycin analog)-bound open states. These structures, combined with electrophysiology, elucidate the molecular details of ligand binding and provide structural insight into how the TRPML1 channel integrates two distantly bound ligand stimuli and facilitates channel opening.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Magnetism and spin dynamics in room-temperature van der Waals magnet Fe 5 GeTe 2

Two-dimensional van der Waals (vdWs) materials have gathered a lot of attention recently. However, the majority of these materials have Curie temperatures that are well below room temperature, making it challenging to incorporate them into device applications. In this work, we synthesized a room-temperature vdW magnetic crystal Fe 5 GeTe 2 with a Curie temperature T c = 332 K, and studied its magnetic properties by vibrating sample magnetometry (VSM) and broadband ferromagnetic resonance (FMR) spectroscopy. The experiments were performed with external magnetic fields applied along the c -axis (H∥ c ) and the ab -plane (H∥ ab ), with temperatures ranging from 300 to 10 K. We have found a sizable Landé g -factor difference between the H∥ c and H∥ ab cases. In both cases, the Landé g -factor values deviated from g = 2. This indicates contribution of orbital angular momentum to the magnetic moment. The FMR measurements reveal that Fe 5 GeTe 2 has a damping constant comparable to Permalloy. With reducing temperature, the linewidth was broadened. Together with the VSM data, our measurements indicate that Fe 5 GeTe 2 transitions from ferromagnetic to ferrimagnetic at lower temperatures. Our experiments highlight key information regarding the magnetic state and spin scattering processes in Fe 5 GeTe 2 , which promote the understanding of magnetism in Fe 5 GeTe 2 , leading to implementations of Fe 5 GeTe 2 based room-temperature spintronic devices.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on V(Bi5O8)5 by Materials Project

Bi25VO40 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. V5+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.75 Å) and two longer (1.76 Å) V–O bond length. There are thirteen inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.11–2.79 Å. In the second Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.12–2.81 Å. In the third Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.11–2.83 Å. In the fourth Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.13–2.78 Å. In the fifth Bi3+ site, Bi3+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with four BiO5 square pyramids and a cornercorner with one BiO4 tetrahedra. There are a spread of Bi–O bond distances ranging from 2.12–2.61 Å. In the sixth Bi3+ site, Bi3+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with eight BiO5 square pyramids and a cornercorner with one BiO4 tetrahedra. There are a spread of Bi–O bond distances ranging from 2.10–2.56 Å. In the seventh Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.12–2.75 Å. In the eighth Bi3+ site, Bi3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.11–2.79 Å. In the ninth Bi3+ site, Bi3+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with six BiO5 square pyramids, a cornercorner with one BiO4 tetrahedra, and an edgeedge with one BiO5 square pyramid. There are a spread of Bi–O bond distances ranging from 2.11–2.53 Å. In the tenth Bi3+ site, Bi3+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with six BiO5 square pyramids, a cornercorner with one BiO4 tetrahedra, and an edgeedge with one BiO5 square pyramid. There are a spread of Bi–O bond distances ranging from 2.11–2.54 Å. In the eleventh Bi3+ site, Bi3+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with six BiO5 square pyramids and a cornercorner with one BiO4 tetrahedra. There are a spread of Bi–O bond distances ranging from 2.10–2.56 Å. In the twelfth Bi3+ site, Bi3+ is bonded to five O2- atoms to form distorted BiO5 square pyramids that share corners with six BiO5 square pyramids and a cornercorner with one BiO4 tetrahedra. There are a spread of Bi–O bond distances ranging from 2.11–2.60 Å. In the thirteenth Bi3+ site, Bi3+ is bonded to four O2- atoms to form corner-sharing BiO4 tetrahedra. There are two shorter (2.27 Å) and two longer (2.29 Å) Bi–O bond lengths. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one V5+ and three Bi3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Bi3+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ atoms. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one V5+ and three Bi3+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ atoms. In the ninth O2- site, O2- is bonded in a trigonal planar geometry to three Bi3+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ atoms. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ atoms. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ atoms. In the fourteenth O2- site, O2- is bonded in a trigonal planar geometry to three Bi3+ atoms. In the fifteenth O2- site, O2- is bonded in a trigonal planar geometry to three Bi3+ atoms. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Bi3+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ atoms. In the eighteenth O2- site, O2- is bonded to four Bi3+ atoms to form corner-sharing OBi4 tetrahedra. In the nineteenth O2- site, O2- is bonded to four Bi3+ atoms to form corner-sharing OBi4 tetrahedra. In the twentieth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Bi3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on AlZnB5H20C5(NO2)5 by Materials Project

Al(BO2)5ZnH20(CN)5 crystallizes in the triclinic P1 space group. The structure is three-dimensional and consists of two ZnH20(CN)5 clusters and one Al(BO2)5 framework. In one of the ZnH20(CN)5 clusters, Zn2+ is bonded in a trigonal bipyramidal geometry to five N3- atoms. There are a spread of Zn–N bond distances ranging from 2.09–2.20 Å. There are five inequivalent C1- sites. In the first C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.47 Å. Both C–H bond lengths are 1.10 Å. In the second C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the third C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the fourth C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the fifth C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. There are five inequivalent N3- sites. In the first N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. Both N–H bond lengths are 1.03 Å. In the second N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. There is one shorter (1.03 Å) and one longer (1.04 Å) N–H bond length. In the third N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. Both N–H bond lengths are 1.02 Å. In the fifth N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. Both N–H bond lengths are 1.03 Å. There are twenty inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventeenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the nineteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twentieth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In one of the ZnH20(CN)5 clusters, Zn2+ is bonded in a trigonal bipyramidal geometry to five N3- atoms. There are a spread of Zn–N bond distances ranging from 2.07–2.22 Å. There are five inequivalent C1- sites. In the first C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the second C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the third C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the fourth C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. In the fifth C1- site, C1- is bonded in a distorted trigonal non-coplanar geometry to one N3- and two H1+ atoms. The C–N bond length is 1.48 Å. Both C–H bond lengths are 1.10 Å. There are five inequivalent N3- sites. In the first N3- site, N3- is bonded in a 4-coordinate geometry to one Zn2+, one C1-, and two H1+ atoms. There is one shorter (1.03 Å) and one longer (1.04 Å) N–H bond length. In the second N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. There is one shorter (1.03 Å) and one longer (1.04 Å) N–H bond length. In the third N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. Both N–H bond lengths are 1.02 Å. In the fourth N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fifth N3- site, N3- is bonded to one Zn2+, one C1-, and two H1+ atoms to form distorted corner-sharing NZnH2C tetrahedra. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. There are twenty inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C1- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventeenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the nineteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twentieth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the Al(BO2)5 framework, there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Al–O bond distances ranging from 1.74–1.76 Å. In the second Al3+ site, Al3+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Al–O bond distances ranging from 1.74–1.76 Å. There are ten inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.41 Å. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. In the third B3+ site, B3+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.48 Å) and two longer (1.49 Å) B–O bond length. In the fourth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.42 Å. In the fifth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.34–1.42 Å. In the sixth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.34–1.41 Å. In the seventh B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.41 Å. In the eighth B3+ site, B3+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. In the ninth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.41 Å. In the tenth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.36–1.41 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one Al3+ and one B3+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the third O2- site, O2- is bonded in a linear geometry to one Al3+ and one B3+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the eighth O2- site, O2- is bonded in a linear geometry to one Al3+ and one B3+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the tenth O2- site, O2- is bonded in a linear geometry to one Al3+ and one B3+ atom. In the eleventh O2- site, O2- is bonded in a linear geometry to one Al3+ and one B3+ atom. In the twelfth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one B3+ atom. In the fourteenth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the sixteenth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the seventeenth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one B3+ atom. In the nineteenth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the twentieth O2- site, O2- is bonded in a linear geometry to one Al3+ and one B3+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Discovery of a Ferromagnetic Nickel Chalcogenide Nanocluster Ni 3 S 3 H(PEt 3 ) 5

Atomically precise ligated nanoclusters (NC) are promising cluster-based materials with novel molecular architectures and tunable magnetic properties. Herein, the synthesis and characterization of a nickel sulfide NC Ni 3 S 3 H(PEt 3 ) 5 (PEt 3 = triethylphosphine) with distinct magnetic properties are reported. Magnetization measurements reveal its magnetic moment of 1.5 µ B in the solid phase, consistent with the existence of one unpaired electron predicted by density functional theory (DFT) calculations. Additionally, experimental measurements indicate the presence of ferromagnetic ordering within each Ni 3 S 3 H(PEt 3 ) 5 NC and strong coercivity at temperatures below 20 K. Ion mobility-mass spectrometry is employed in conjunction with DFT calculations and collision cross-section simulations to investigate the structure of the isolated Ni 3 S 3 H(PEt 3 ) 5 . Theoretical studies show that [Ni 3 S 3 H(PEt 3 ) 5 ] + has a planar Ni 3 S 3 core where three Ni atoms are arranged in a triangle with three bridging S atoms residing in the same plane. This structure is preserved in both solution and solid phases, which is confirmed by spectroscopic studies of Ni 3 S 3 H(PEt 3 ) 5 . Additionally, DFT calculations indicate that all spins at the Ni sites are aligned parallel, confirming the presence of ferromagnetic coupling. Overall, this study provides key insights into the structure and magnetic properties of Ni 3 S 3 H(PEt 3 ) 5 , which will facilitate the design of new NC-based magnetic materials.

Nickel sulfide nanocluster↗

DOE OSTI2020

Reactor and fuel cycle performance of light water reactor fuel with 235 U enrichments above 5%

Recent advances in nuclear fuel materials research, particularly on the topic of accident-tolerant fuels, have brought up potential opportunities for expanding the operating envelope of existing light water reactors. As many of the performance improvements offered by these technologies may be most fully realized by increasing fuel enrichment beyond the standard 5% limit, this paper examines the potential reactor performance and fuel cycle performance of low-enriched uranium oxide fueled light water reactors by generically considering pressurized water reactors with 235 U enrichment from 5 to 7%. Advanced cladding, including accident-tolerant cladding, has the potential to increase fuel burnup limits related to hydrogen in the cladding that coincide with those limits associated with end-of-life reactivity. Therefore, higher enrichment will be necessary in order to realize the higher fuel burnups. This work includes evaluation of the fuel cycle length, discharge burnup, reactivity coefficients, and fuel cycle performance, including radioactive waste and environmental impact metrics per unit energy generated. The analysis was performed using the evaluation metrics from the US Department of Energy Office of Nuclear Energy Fuel Cycle Evaluation and Screening Study. The reactor performance and safety analysis show that enrichments between 5 and 7% would have similar fuel temperature and moderator temperature coefficients. However, the soluble boron coefficient would decrease in magnitude, requiring more corrosive boric acid in the coolant or other methods of reactivity control during the fuel cycle. At these higher enrichments the maximum burnup at the rim of the fuel pellet would increase by almost a factor of two, which is expected to impact the formation of high-burnup structure in the fuel and the corresponding thermo-mechanical fuel properties. The fuel cycle performance assessment shows that increasing enrichment reduces the quantity of high-level waste disposed per unit energy generated, but it increases the natural resource requirements normalized to a gigawatt-electricity-per-year basis. Another impact is the slightly higher discharge burnup, resulting in somewhat different activity levels of the spent nuclear fuel and high-level waste radioactivity at 100 and 100,000 years after fuel discharge. The environmental impacts—including land use, water use, carbon emission, and radiological exposure—are of the same magnitude per unit energy generated. Finally, however, the impacts are distributed differently. Less than 5% enrichment has marginally more impact on the back-end of the fuel cycle, and greater than 5% enrichment has marginally more impact on the front-end of the fuel cycle. Ultimately, no neutronic or reactor safety hindrances to employing light water reactor fuel with enrichments greater than 5% are identified; given the achievable reactor performance benefits with advanced fuels, further practical exploration of increased enrichment fuel is recommended.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2021

The effects of SMSI on m-Cresol Hydrodeoxygenation over Pt/Nb 2 O 5 and Pt/TiO 2

The hydrodeoxygenation (HDO) of m-cresol was studied on Pt/Nb 2 O 5 /MgAl 2 O 4 and Pt/TiO 2 /MgAl 2 O 4 catalysts to understand the effects of Strong Metal Support Interactions (SMSI). The Nb 2 O 5 and TiO 2 supports were prepared as 0.7-nm films on MgAl 2 O 4 by Atomic Layer Deposition (ALD) to ensure that the structures of the catalyst were the same. When reduced at 773 K to place Pt in the encapsulated state, Pt/Nb 2 O 5 /MgAl 2 O 4 was much less active than Pt/MgAl 2 O 4 at 573 K but much more active at 623 K. While Pt/MgAl 2 O 4 deactivated rapidly due to coking, Pt/Nb 2 O 5 /MgAl 2 O 4 showed significantly better coke tolerance and was almost 100% selective towards toluene production. Pt/Nb 2 O 5 /MgAl 2 O 4 reduced at lower temperatures exhibited intermediate catalytic properties. The effect of reduction temperature on Pt/TiO 2 /MgAl 2 O 4 was much less and this catalyst was more similar to Pt/MgAl 2 O 4 than its Nb 2 O 5 counterpart. Lastly, the implications of these results for understanding the nature of oxide promoters on HDO of m-cresol are discussed.

09 BIOMASS FUELS↗

DOE OSTI2023

Locating anionic hydrogen in Ba 3 (Yb,Lu) 2 O 5 H 2 : A combined approach of X-ray diffraction, crystal chemistry, and DFT calculations

By a combination of x-ray diffraction, structural chemistry, and DFT calculations, the presence and location of anionic hydrogen in the two new, layered lanthanide oxyhydrides, Ba 3 Ln 2 O 5 H 2 (Ln = Yb, Lu) is inferred. Single crystals of the compounds have been synthesized from a molten barium flux with the addition of small amounts of BaH 2 . These phases crystallize in space group I4/mmm (#139, Z = 2) with lattice parameters a = 4.3336(2) Å and c = 22.7197(6) Å, and a = 4.3291(1) Å and c = 22.597(1) Å, respectively. The Ba 3 Ln 2 O 5 H 2 phases comprise two different structural moieties: a perovskite double layer of stoichiometry Ba 2 Ln 2 O 5 H – formed by corner-connected LnO 5 tetragonal bi-pyramids with a terminating hydrogen anion, and a puckered rocksalt-type (BaH) + layer that is stretched along the c-axis. DFT calculations were used to arrive at hydrogen positions that minimize energy and are consistent with structural chemistry principles. Furthermore, the calculations show that the valence band edge is dominated by oxygen 2p orbitals with hydrogen 1s states admixed. The conduction band is formed by barium 5d-orbitals and Lu (Yb) 5d-orbitals. These are characteristics of materials with anionic H – . These new phases are isostructural with the Ba 3 Ln 2 O 5 Cl 2 (Ln = Gd–Lu) family of compounds with the chlorine atom in the same apical position as the hydrogen atom. Finally, steric effects limit the size of the lanthanide ion for Ba 3 Ln 2 O 5 H 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

All-Inorganic Open-Framework Chalcogenides, A 3 Ga 5 S 9 · x H 2 O ( A = Rb and Cs), Exhibiting Ultrafast Uranyl Remediation and Illustrating a Novel Post-Synthetic Preparation of Open-Framework Oxychalcogenides

Fast and effective uranyl sequestration is of interest to the nuclear industry. Recently layered chalcogenide materials have demonstrated fast, selective, and efficient sorption properties towards uranyl cations and the development and investigation of new types of chalcogenide materials continues to be of interest and represents an intriguing option for uranyl remediation. Three new all-inorganic A 3 Ga 5 S 9 ·xH 2 O (A = Rb, Rb/Cs, and Cs) open-framework chalcogenides were obtained via an in-situ alkali carbonate to alkali sulfide conversion process achieved under mild hydrothermal conditions. The structures of the all-inorganic open framework chalcogenides consist of a 2-fold interpenetrated diamond-like 3D framework containing pseudo-T 3 [Ga 10 S 20 ] 10– supertetrahedra. 48% of the structural volume is occupied by A + cations and water species, as established by single-crystal X-ray diffraction (SCXRD), infrared (IR) and energy-dispersive (EDS) spectroscopies. The dynamic nature of the A + cations and water molecules within the pores was investigated via single crystal X-ray diffraction as well as by IR spectroscopy monitored H 2 O to D 2 O exchange experiments. Framework stability was probed with post-synthetic treatment of A 3 Ga 5 S 9 ·xH 2 O (A = Rb and Cs) samples in acidic solutions that resulted in the formation of the oxysulfide (A/H) 3 Ga 5 S 9–y O y ·xH 2 O (A = Rb and Cs; y = 0–1), as shown by SCXRD and IR. Ion-exchange studies on A 3 Ga 5 S 9 ·xH 2 O (A = Rb and Cs) samples were carried out utilizing a uranyl acetate solution. The presence of the UO 2 2+ species in the ion-exchanged product was supported by IR and EDS spectroscopies. Batch method ion-exchange experiments on Cs 3 Ga 5 S 9 ·xH 2 O powder demonstrated fast kinetics with 95% uranyl removal from the uranyl acetate solution during the first minute, a maximum uranyl uptake capacity of 15mg/g, and the subsequent elution of uranyl species with KCl solution. Furthermore, the porous and dynamic nature of the A 3 Ga 5 S 9 ·xH 2 O framework coupled with effective UO 2 2+ ···S 2– bonding interactions makes it a good potential sorbent for uranyl remediation from aqueous media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Toggling Stereochemical Activity through Interstitial Positioning of Cations between 2D V 2 O 5 Double Layers

The 5/6s 2 lone-pair electrons of p-block cations in their lower oxidation states are a versatile electronic and geometric structure motif that can underpin lattice anharmonicity and often engender electronic and structural instabilities that underpin the function of active elements in nonlinear optics, thermochromics, thermoelectrics, neuromorphic computing, and photocatalysis. In contrast to periodic solids where lone-pair-bearing cations are part of the structural framework, installing lone-pair-bearing cations in the interstitial sites of intercalation hosts provides a means of a systematically modulating electronic structure through the choice of the group and the period of the inserted cation while preserving the overall framework connectivity. The extent of stereochemical activity and the energy positioning of lone-pair-derived mid-gap states depend on the cation identity, stoichiometry, and strength of anion hybridization. V 2 O 5 polymorphs are versatile insertion hosts that can accommodate a broad range of s-, p-, and d-block cations. However, the insertion of lone-pair-bearing cations remains largely underexplored. In this article, we examine the implications of varying the 6s 2 cations situated in interlayer sites between condensed [V 4 O 10 ] n double layers. Systematic modulations of lattice distortions, electronic structure, and magnetic ordering are observed with increasing strength of stereochemical activity from group 12 to group 14 cations. We compare and contrast p-block-layered M x V 2 O 5 (M = Hg, Tl, and Pb) compounds and map the significance of local off-centering arising from the stereochemical activity of lone-pair cations to the emergence of filled antibonding lone-pair 6s 2 –O 2p-hybridized mid-gap states mediated by second-order Jahn–Teller distortions. Crystallographic studies of cation coordination environments and the resulting modulation of V–V interactions have been used in conjunction with variable-energy hard X-ray photoelectron spectroscopy measurements, first-principles electronic structure calculations, and crystal orbital Hamilton population analyses to decipher the origins of stereochemical activity. Magnetic susceptibility measurements reveal antiferromagnetic signatures for all the three compounds. However, the differences in V–V interactions significantly affect the energy balance of the superexchange interactions, resulting in an ordering temperature of 160 and 260 K for Hg 0.5 V 2 O 5 and δ-Tl 0.5 V 2 O 5 , respectively, as compared to 7 K for δ-Pb 0.5 V 2 O 5 . In δ-Pb 0.5 V 2 O 5 , the strong stereochemical activity of electron lone pairs and the resulting electrostatic repulsions enforce superlattice ordering, which strongly modifies the electronic localization patterns along the [V 4 O 10 ] slabs, resulting in disrupted magnetic ordering and an anomalously low ordering temperature. The results demonstrate a versatile strategy for toggling the stereochemical activity of electron lone pairs to modify the electronic structure near the Fermi level and to mediate superexchange interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Unraveling the Origin of Photocatalytic Deactivation in CeO 2 /Nb 2 O 5 Heterostructure Systems during Methanol Oxidation: Insight into the Role of Cerium Species

The study provides deep insight into the origin of photocatalytic deactivation of Nb 2 O 5 after modification with ceria. Of particular interest was to fully understand the role of ceria species in diminishing the photocatalytic performance of CeO 2 /Nb 2 O 5 heterostructures. For this purpose, ceria was loaded on niobia surfaces by wet impregnation. The as-prepared materials were characterized by powder X-ray diffraction, nitrogen physisorption, UV-visible spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and photoluminescence measurements. Photocatalytic activity of parent metal oxides (i.e., Nb 2 O 5 and CeO 2 ) and as-prepared CeO 2 / Nb 2 O 5 heterostructures with different ceria loadings were tested in methanol photooxidation, a model gas-phase reaction. Deep insight into the photocatalytic process provided by operando-IR techniques combined with results of photoluminescence studies revealed that deactivation of CeO 2 /Nb 2 O 5 heterostructures resulted from increased recombination of photo-excited electrons and holes. The main factor contributing to more efficient recombination of the charge carriers in the heterostructures was the ultrafine size of the ceria species. The presence of such highly dispersed ceria species on the niobia surface provided a strong interface between these two semiconductors, enabling efficient charge transfer from Nb 2 O 5 to CeO 2 . However, the ceria species supported on niobia exhibited a high defect site concentration, which acted as highly active recombination centers for the photo-induced charge carriers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Highly Efficient Surface Charge Transfer in Fe 2 TiO 5 Epitaxial Thin Film Photoanodes

Pseudobrookite (Fe 2 TiO 5 ) has attracted significant attention as an emerging photoanode for water oxidation due to reports of enhanced performance in polycrystalline heterostructures with α-Fe 2 O 3 or TiO 2 . However, the specific properties and contribution of Fe 2 TiO 5 remain unknown. Here, we present the first photoelectrochemical characterization of epitaxial thin film Fe 2 TiO 5 , an ideal platform for probing the inherent response of this earth-abundant photoanode for solar water splitting. Moreover, by using an electrolyte containing a hole scavenger, we find highly efficient charge transfer at the Fe 2 TiO 5 –electrolyte interface. This notable surface property is exploited in the form of an Fe 2 TiO 5 /α-Fe 2 O 3 heterostructure photoanode, for which we observe a photocurrent density increase by 1 order of magnitude and an onset potential improvement by ~300 mV. Establishing these fundamental properties elucidates the nature of reaction mechanisms on Fe 2 TiO 5 and informs the design of highly efficient water photo-oxidation devices by incorporating this material with other photoanodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Multinonmetal-Doped V 2 O 5 Nanocomposites for Lithium-Ion Battery Cathodes

Lithium-ion batteries (LIBs) are critical for portable electronics and electric vehicles, demanding higher energy density to meet increasing energy storage needs. Current commercial cathode materials, such as LiFePO 4 and LiCoO 2 , are limited by a single electron transfer, restricting their energy density. Vanadium pentoxide (V 2 O 5 ) emerges as a promising high-capacity cathode due to its high theoretical capacity of 443 mA h g –1 with three Li storage capacities, significantly surpassing conventional materials. However, the practical application of V 2 O 5 is hindered by a large structural evolution and rapid capacity fading during full lithium intercalation. Here, this study introduces a multinonmetal doping (MNM) strategy to enhance V 2 O 5 cathodes by incorporating all-nonmetal dopants (B, P, and Si) and graphene (G). MNM-V 2 O 5 -G exhibits increased surface oxygen defects, improving charge transfer kinetics and thus enhancing the rate performance and cycling stability. Our results provide valuable insights into the role of surface oxygen defects in stabilizing V 2 O 5 with element doping. This research highlights the potential of multinonmetal doping to improve LIB cathode materials, offering a promising pathway for design of high-energy-density V 2 O 5 cathodes and advancing the development of next-generation energy storage solutions.

25 ENERGY STORAGE↗

DOE OSTI2025

Electrochemical Phase Engineering of γ′-V 2 O 5 Thin Films for Sodium-Ion Storage Electrodes

V 2 O 5 is a promising sodium-ion cathode material due to its high theoretical capacity (147 mAh/g) and working voltage (3.3 V vs Na/Na + ). Among its various crystal phases, γ′-V 2 O 5 has a large interlayer spacing, ensuring the reversible insertion–extraction of sodium ions. However, current synthesis methods for γ′-V2O5 require high temperatures (>600 °C) and toxic chemicals (NO 2 BF 4 ), which make the preparation demanding. Herein, we put forward an electrochemical phase engineering method combining thermal annealing and electrochemistry to easily prepare thin-film γ′-V 2 O 5 . Electrochemical characterization shows near-ideal performance as a thin-film cathode material for sodium-ion batteries. It shows a measured initial capacity of 152 mAh/g, a high working voltage (3.3 V vs Na + /Na), and an exceptional Coulombic efficiency of 98%, significantly surpassing previously reported values (∼50% CE). Cyclic voltammogram and galvanostatic capacity curves confirm the sodium insertion–deinsertion, which remains stable at 2 C. The γ′-V 2 O 5 thin film has electrochemical performance similar to γ′-V 2 O 5 powder, indicating another workable morphology of γ′-V 2 O 5 for sodium-ion batteries.

batteries↗

DOE OSTI2023

Prediction of the structures and heats of formation of MO 2 , MO 3 , and M 2 O 5 for M = V, Nb, Ta, Pa

Structures for the mono-, di-, and tri-bridge isomers of M 2 O 5 as well as those for the MO 2 and MO 3 fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. Here, the lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa. The di-bridge isomers were predicted to be composed of MO 2 + and MO 3 - fragments, whereas the mono- and tri-bridge are two MO 2 + fragments linked by an O 2 - . The heats of formation of M 2 O 5 dimers, as well as MO 2 and MO 3 neutral and ionic species were predicted using the Feller–Peterson–Dixon (FPD) approach. The heats of formation of the MF 5 species were calculated to provide additional benchmarks. Dimerization energies to form the M 2 O 5 dimers are predicted to become more negative going down group 5 and range from -29 to -45 kcal mol -1 . The ionization energies (IEs) for VO 2 and TaO 2 are essentially the same at 8.75 eV whereas the IEs for NbO 2 and PaO 2 are 8.10 and 6.25 eV, respectively. The predicted adiabatic electron affinities (AEAs) range from 3.75 eV to 4.45 eV for the MO 3 species and vertical detachment energies from 4.21 to 4.59 eV for MO 3 - . The calculated M[double bond, length as m-dash]O bond dissociation energies increase from 143 kcal mol -1 for M = V to ~170 kcal mol -1 for M = Nb and Ta to ~200 kcal mol -1 for M = Pa. The M–O bond dissociation energies are all similar ranging from 97 to 107 kcal mol -1 . Natural bond analysis provided insights into the types of chemical bonds in terms of their ionic character. Pa 2 O 5 is predicted to behave like an actinyl species dominated by the interactions of approximately linear PaO 2 + groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗