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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

The Energy and Operational Impacts of Using 0-10V Control for LED Streetlights

Lighting systems have historically utilized either a proprietary control method, or one of a handful of standardized methods (e.g., 0-10V, DALI, DMX512) aimed at facilitating vendor interoperability. The utility and market success of the standardized methods has been limited for a variety of reasons. Although 0-10V is presently the most commonly available control interface for indoor and outdoor products in North America – even after the emergence of LED products and “connected lighting systems” with more modern network interfaces and luminaire-level sensors and intelligence – the use of 0-10V methods has significant tradeoffs. For instance, it is difficult to predict relative luminaire light output and input power at any particular control voltage, and performance across luminaires is inconsistent. This study characterizes 23 LED streetlights that claimed dimmability via a 0-10V interface, quantifies the performance variation found in market-available LED drivers, and explores the potential impact of the most recent 0-10V voluntary standard (ANSI C137.1-2022). Notably, the tested products were all manufactured prior to the release of this standard, and thus do not make compliance claims. Variation in response to 0-10V control voltages was expected to be more significant across different make/model luminaires than different units of the same make/model; the test population was structured based on this expectation. The 23 tested luminaires comprised 21 unique make/model streetlights from 14 different manufacturers. Three samples of one make/model streetlight were included in the test population to facilitate a limited exploration of unit-to-unit variation. The 21 unique make/model luminaires contained 20 unique make/model LED drivers from eight different driver manufacturers. Luminaire input power and current were measured at 11 control voltages (0.5 V and 1–10 V in 1 V increments).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Materials Data on V(MoS2)2 by Materials Project

VMo2S4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eight inequivalent V4+ sites. In the first V4+ site, V4+ is bonded to five S2- atoms to form distorted VS5 square pyramids that share a cornercorner with one VS6 octahedra, corners with three MoS6 octahedra, an edgeedge with one VS6 octahedra, an edgeedge with one MoS6 octahedra, an edgeedge with one VS5 trigonal bipyramid, and an edgeedge with one MoS5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 20–88°. There are a spread of V–S bond distances ranging from 2.32–2.44 Å. In the second V4+ site, V4+ is bonded to five S2- atoms to form distorted VS5 trigonal bipyramids that share a cornercorner with one VS6 octahedra, corners with four MoS6 octahedra, a cornercorner with one VS5 trigonal bipyramid, a cornercorner with one MoS5 trigonal bipyramid, an edgeedge with one VS6 octahedra, an edgeedge with one MoS6 octahedra, and edges with two MoS5 square pyramids. The corner-sharing octahedra tilt angles range from 32–67°. There are a spread of V–S bond distances ranging from 2.29–2.49 Å. In the third V4+ site, V4+ is bonded to five S2- atoms to form VS5 trigonal bipyramids that share a cornercorner with one VS6 octahedra, corners with four MoS6 octahedra, a cornercorner with one VS5 trigonal bipyramid, a cornercorner with one MoS5 trigonal bipyramid, edges with two MoS6 octahedra, and an edgeedge with one VS5 square pyramid. The corner-sharing octahedra tilt angles range from 40–61°. There are a spread of V–S bond distances ranging from 2.30–2.38 Å. In the fourth V4+ site, V4+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of V–S bond distances ranging from 2.27–2.77 Å. In the fifth V4+ site, V4+ is bonded to six S2- atoms to form distorted VS6 octahedra that share corners with three MoS6 octahedra, a cornercorner with one VS5 square pyramid, corners with two VS5 trigonal bipyramids, corners with two equivalent MoS5 trigonal bipyramids, an edgeedge with one MoS6 octahedra, edges with two MoS5 square pyramids, an edgeedge with one VS5 trigonal bipyramid, and a faceface with one MoS6 octahedra. The corner-sharing octahedra tilt angles range from 22–33°. There are a spread of V–S bond distances ranging from 2.38–2.68 Å. In the sixth V4+ site, V4+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of V–S bond distances ranging from 2.26–2.80 Å. In the seventh V4+ site, V4+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of V–S bond distances ranging from 2.25–2.84 Å. In the eighth V4+ site, V4+ is bonded to six S2- atoms to form distorted VS6 octahedra that share corners with two equivalent MoS6 octahedra, a cornercorner with one MoS5 square pyramid, a cornercorner with one MoS5 trigonal bipyramid, edges with three MoS6 octahedra, and an edgeedge with one VS5 square pyramid. The corner-sharing octahedra tilt angles range from 13–15°. There are a spread of V–S bond distances ranging from 2.30–2.57 Å. There are sixteen inequivalent Mo2+ sites. In the first Mo2+ site, Mo2+ is bonded to six S2- atoms to form MoS6 octahedra that share a cornercorner with one MoS6 octahedra, corners with two equivalent VS6 octahedra, a cornercorner with one MoS5 square pyramid, a cornercorner with one VS5 trigonal bipyramid, a cornercorner with one MoS5 trigonal bipyramid, an edgeedge with one MoS5 square pyramid, an edgeedge with one VS5 trigonal bipyramid, and a faceface with one MoS6 octahedra. The corner-sharing octahedra tilt angles range from 22–51°. There are a spread of Mo–S bond distances ranging from 2.33–2.60 Å. In the second Mo2+ site, Mo2+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share corners with two MoS6 octahedra, a cornercorner with one VS5 square pyramid, corners with two equivalent VS5 trigonal bipyramids, edges with two MoS6 octahedra, and edges with two MoS5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 19–40°. There are a spread of Mo–S bond distances ranging from 2.29–2.59 Å. In the third Mo2+ site, Mo2+ is bonded to five S2- atoms to form distorted MoS5 trigonal bipyramids that share a cornercorner with one MoS6 octahedra, corners with two equivalent VS6 octahedra, a cornercorner with one VS5 trigonal bipyramid, and edges with three MoS6 octahedra. The corner-sharing octahedra tilt angles range from 10–60°. There are a spread of Mo–S bond distances ranging from 2.31–2.58 Å. In the fourth Mo2+ site, Mo2+ is bonded to five S2- atoms to form distorted MoS5 trigonal bipyramids that share a cornercorner with one VS6 octahedra, a cornercorner with one MoS6 octahedra, a cornercorner with one VS5 trigonal bipyramid, edges with three MoS6 octahedra, and an edgeedge with one VS5 square pyramid. The corner-sharing octahedra tilt angles range from 31–77°. There are a spread of Mo–S bond distances ranging from 2.33–2.52 Å. In the fifth Mo2+ site, Mo2+ is bonded to six S2- atoms to form MoS6 octahedra that share corners with three MoS6 octahedra, a cornercorner with one VS5 square pyramid, corners with two MoS5 square pyramids, corners with two equivalent VS5 trigonal bipyramids, an edgeedge with one VS5 trigonal bipyramid, an edgeedge with one MoS5 trigonal bipyramid, a faceface with one VS6 octahedra, and a faceface with one MoS6 octahedra. The corner-sharing octahedra tilt angles range from 40–58°. There are a spread of Mo–S bond distances ranging from 2.34–2.52 Å. In the sixth Mo2+ site, Mo2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Mo–S bond distances ranging from 2.34–2.99 Å. In the seventh Mo2+ site, Mo2+ is bonded to five S2- atoms to form distorted MoS5 square pyramids that share a cornercorner with one VS6 octahedra, a cornercorner with one MoS6 octahedra, corners with two equivalent MoS5 square pyramids, an edgeedge with one VS6 octahedra, edges with three MoS6 octahedra, and an edgeedge with one VS5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 10–45°. There are a spread of Mo–S bond distances ranging from 2.34–2.62 Å. In the eighth Mo2+ site, Mo2+ is bonded in a 5-coordinate geometry to five S2- atoms. There are a spread of Mo–S bond distances ranging from 2.36–2.85 Å. In the ninth Mo2+ site, Mo2+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share a cornercorner with one MoS6 octahedra, corners with two equivalent VS6 octahedra, edges with three MoS6 octahedra, and an edgeedge with one MoS5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 13–19°. There are a spread of Mo–S bond distances ranging from 2.36–2.64 Å. In the tenth Mo2+ site, Mo2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Mo–S bond distances ranging from 2.27–2.93 Å. In the eleventh Mo2+ site, Mo2+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share a cornercorner with one VS5 square pyramid, a cornercorner with one VS5 trigonal bipyramid, a cornercorner with one MoS5 trigonal bipyramid, an edgeedge with one VS6 octahedra, edges with two MoS6 octahedra, and an edgeedge with one MoS5 trigonal bipyramid. There are a spread of Mo–S bond distances ranging from 2.41–2.67 Å. In the twelfth Mo2+ site, Mo2+ is bonded to six S2- atoms to form MoS6 octahedra that share a cornercorner with one MoS6 octahedra, a cornercorner with one VS5 trigonal bipyramid, an edgeedge with one VS6 octahedra, an edgeedge with one MoS6 octahedra, an edgeedge with one VS5 square pyramid, an edgeedge with one VS5 trigonal bipyramid, and an edgeedge with one MoS5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 58°. There are a spread of Mo–S bond distances ranging from 2.40–2.60 Å. In the thirteenth Mo2+ site, Mo2+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share a cornercorner with one VS6 octahedra, an edgeedge with one VS6 octahedra, edges with three MoS6 octahedra, and edges with two MoS5 square pyramids. The corner-sharing octahedral tilt angles are 24°. There are a spread of Mo–S bond distances ranging from 2.37–2.70 Å. In the fourteenth Mo2+ site, Mo2+ is bonded to five S2- atoms to form distorted MoS5 square pyramids that share corners with two MoS6 octahedra, corners with two equivalent MoS5 square pyramids, an edgeedge with one VS6 octahedra, edges with two MoS6 octahedra, and an edgeedge with one VS5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 56–82°. There are a spread of Mo–S bond distances ranging from 2.38–2.72 Å. In the fifteenth Mo2+ site, Mo2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Mo–S bond distances ranging from 2.32–2.93 Å. In the sixteenth Mo2+ site, Mo2+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share a cornercorner with one VS5 trigonal bipyramid, an edgeedge with one VS6 octahedra, edges with three MoS6 octahedra, and edges with two MoS5 square pyramids. There are a spread of Mo–S bond distances ranging from 2.36–2.68 Å. There are thirty-two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to two V4+ and three Mo2+ atoms. In the second S2- site, S2- is bonded in a 4-coordinate geometry to two V4+ and three Mo2+ atoms. In the third S2- site, S2- is bonded to one V4+ and three Mo2+ atoms to form distorted edge-sharing SVMo3 tetrahedra. In the fourth S2- site, S2- is bonded in a distorted L-shaped geometry to two Mo2+ atoms. In the fifth S2- site, S2- is bonded to four Mo2+ atoms to form distorted edge-sharing SMo4 trigonal pyramids. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to three V4+ and two Mo2+ atoms. In the seventh S2- site, S2- is bonded in a 5-coordinate geometry to two V4+ and three Mo2+ atoms. In the eighth S2- site, S2- is bonded in a 4-coordinate geometry to two V4+ and two Mo2+ atoms. In the ninth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four Mo2+ atoms. In the tenth S2- site, S2- is bonded in a 4-coordinate geometry to two V4+ and two Mo2+ atoms. In the eleventh S2- site, S2- is bonded in a 5-coordinate geometry to two V4+ and three Mo2+ atoms. In the twelfth S2- site, S2- is bonded in a 6-coordinate geometry to three V4+ and three Mo2+ atoms. In the thirteenth S2- site, S2- is bonded in a 5-coordinate geometry to two V4+ and three Mo2+ atoms. In the fourteenth S2- site, S2- is bonded in a 5-coordinate geometry to two V4+ and three Mo2+ atoms. In the fifteenth S2- site, S2- is bonded in a 3-coordinate geometry to three Mo2+ atoms. In the sixteenth S2- site, S2- is bonded in a 4-coordinate geometry to one V4+ and three Mo2+ atoms. In the seventeenth S2- site, S2- is bonded in a 3-coordinate geometry to three Mo2+ atoms. In the eighteenth S2- site, S2- is bonded in a 1-coordinate geometry to one V4+ and three Mo2+ atoms. In the nineteenth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to two V4+ and two Mo2+ atoms. In the twentieth S2- site, S2- is bonded in a 4-coordinate geometry to one V4+ and three Mo2+ atoms. In the twenty-first S2- site, S2- is bonded in a distorted see-saw-like geometry to two V4+ and two Mo2+ atoms. In the twenty-second S2- site, S2- is bonded in a 4-coordinate geometry to one V4+ and three Mo2+ atoms. In the twenty-third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four Mo2+ atoms. In the twenty-fourth S2- site, S2- is bonded in a 4-coordinate geometry to two V4+ and two Mo2+ atoms. In the twenty-fifth S2- site, S2- is bonded in a 4-coordinate geometry to one V4+ and three Mo2+ atoms. In the twenty-sixth S2- site, S2- is bonded to two V4+ and three Mo2+ atoms to form distorted edge-sharing SV2Mo3 square pyramids. In the twenty-seventh S2- site, S2- is bonded in a 4-coordinate geometry to two V4+ and three Mo2+ atoms. In the twenty-eighth S2- site

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V(ClO2)3 by Materials Project

V(O2Cl)3 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two V(O2Cl)3 sheets oriented in the (0, 0, 1) direction. V is bonded in a distorted octahedral geometry to four O and two equivalent Cl atoms. All V–O bond lengths are 1.82 Å. Both V–Cl bond lengths are 2.52 Å. There are three inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.56 Å. In the second O site, O is bonded in a bent 150 degrees geometry to one V and one Cl atom. The O–Cl bond length is 1.81 Å. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one V and one Cl atom. The O–Cl bond length is 1.91 Å. There are two inequivalent Cl sites. In the first Cl site, Cl is bonded in a square co-planar geometry to four O atoms. In the second Cl site, Cl is bonded in a bent 120 degrees geometry to one V and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

In-situ hydrogen microstructural characterization of Si heterojunction passivation: Addressing V OC degradation and mitigation pathways

Si heterojunction (SHJ) solar cells have demonstrated record efficiency >27%, approaching the theoretical limit of ≈ 29%, primarily due to best surface/interface defect passivation provided by deposited thin layers of hydrogenated amorphous silicon (a-Si:H). Such excellent surface/interface passivation reduces recombination loss and result in >100 mV improvement of cell open circuit voltage (V OC ) to ≈ 750 mV, thus the cell efficiency. However, fielded SHJ modules exhibit loss of V OC and hence efficiency over time in years, presumably due to degradation related to a-Si:H layers. This adversely affects the technology’s market acceptance, and levelized cost of energy (LCOE). It is hypothesized that the origin of a-Si:H degradation is somehow related to the presence of weak Si–Si bonds and hydrogen in a-Si:H films. The objective of this project is to test this hypothesis by directly measuring chemical and structural changes occurring within SHJ component layers and solar cells. This is achieved by developing an innovative in-situ Fourier transform infrared (FTIR) spectrometry apparatus to monitor hydrogen microstructural changes occurring within amorphous silicon and decipher hydrogen evolution kinetics over time when samples are exposed to heat and/or light stress. These in-situ measured hydrogen microstructural changes are correlated to the changes in effective minority carrier lifetime (τ eff ), implied V OC (iV OC ), surface recombination velocity (S), and cell V OC . These mechanistic understandings will provide critical guidance to mitigate the V OC -driven degradation of SHJ solar cell performance. Passivation optimization and degradation analysis of individual SHJ component structures were achieved through systematic deposition of three symmetric structures and the completed SHJ solar cell structure. The three symmetric structures used were intrinsic a-Si:H [(i)a-Si:H] layers in a bilayer structure, intrinsic and p-type doped stacked layers [(i-p)a-Si:H] representing the front heterojunction in the SHJ cell, and intrinsic and n-typed doped stacked layers [(i-n)a-Si:H] representing the back-side back surface field (BSF) in the SHJ cell. State-of-the-art passivation qualities are demonstrated by a champion iV OC of 740 mV for the (i)a-Si:H layers, and the (i-n)a-Si:H symmetric structure. A 725 mV iV OC is observed for the (i-p)a-Si:H symmetric structure. These symmetric passivated SHJ component structures were subsequently subjected to different accelerated lifetime (ALT) stressors to identify which conditions contribute the most to iV OC degradation. Degradation of the thin (10 nm) (i)a-Si:H passivation layers without any additional overlying layers is minimal; complexity of this study arises due to unavoidable surface oxidation of (i)a-Si:H layer during most of the stress application, which is likely irrelevant for a full SHJ cell configuration with overlying protective layers. The iV OC degradation of symmetric structures is found to occur primarily at the (i-p)a-Si:H passivation stack under dark heat stress with associated hydrogen loss from the (p)a-Si:H layer. An activation energy for increase in S (defect creation) of 0.65 eV can be correlated to the activation energy of ≈ 0.4 eV for hydrogen loss from the (i-p)a-Si:H stack. This also suggests the presence of weakly bonded hydrogen in the (p)a-Si:H films, which effuses out of the film stack at such low activation energy. When light and heat stress are applied together, similar hydrogen loss from (i-p)a-Si:H stack is observed, however, does not appreciably degrade iV OC or increase S. This is an important result and departure from direct correlation between hydrogen loss and defect creation. This perhaps indicates additional defect chemistries or annealing that might be occurring in the presence of light requiring further detailed defect measurements. The full SHJ cell structure used for this project is depicted in Fig.1(d). SHJ cells with an initial V OC ≈ 700 mV were fabricated and subjected to similar ALT stress conditions. Cell V OC is found to degrade the most under dark heat stress and is confirmed by observed hydrogen migration out of the (i-p)a-Si:H stack. However, hydrogen cannot escape from the cell stack, it accumulates near the (p)a-Si:H/ITO contact interface, where ITO acts as a barrier preventing hydrogen loss. Furthermore, light-heat combined stress does not degrade V OC appreciably, confirming the occurrence of a defect annealing process.

14 SOLAR ENERGY↗
DOE OSTI2021

Anisotropic flow of identified hadrons in $\mathrm{X}$e-$\mathrm{X}$e collisions at $\sqrt{s_{NN}}$ = 5.44 $\mathrm{T}$e$\mathrm{V}$

Measurements of elliptic (v 2 ) and triangular (v 3 ) flow coefficients of π ± , K ± , $p+\bar{p}$, $K$$^{0}_{S}$, and $Λ+\bar{Λ}$ obtained with the scalar product method in Xe-Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV are presented. The results are obtained in the rapidity range |y| < 0.5 and reported as a function of transverse momentum, p T , for several collision centrality classes. The flow coefficients exhibit a particle mass dependence for p T < 3 GeV/c, while a grouping according to particle type (i.e., meson and baryon) is found at intermediate transverse momenta (3 < p T < 8 GeV/c). The magnitude of the baryon v 2 is larger than that of mesons up to p T = 6 GeV/c. The centrality dependence of the shape evolution of the p T -differential v 2 is studied for the various hadron species. The v 2 coefficients of π ± , K ± , and $p+\bar{p}$ are reproduced by MUSIC hydrodynamic calculations coupled to a hadronic cascade model (UrQMD) for p T < 1 GeV/c. A comparison with v n measurements in the corresponding centrality intervals in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV yields an enhanced v 2 in central collisions and diminished value in semicentral collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

NASICON Na 3 V 2 (PO 4 ) 3 Enables Quasi-Two-Stage Na + and Zn 2+ Intercalation for Multivalent Zinc Batteries

Identifying positive electrode materials capable of reversible multivalent electrochemistry in electrolytes containing divalent ions such as Mg 2+ , Ca 2+ , and Zn 2+ at high operating potentials remains an ongoing challenge in “beyond lithium-ion” research. In this paper, we explore the Zn 2+ charge-storage mechanism of a vanadium-based Na + superionic conductor (NASICON), Na 3 V 2 (PO 4 ) 3 . By using X-ray synchrotron techniques to unravel potential-dependent structure–property relationships, we ascribe the reversible electrochemical behavior of Na 3 V 2 (PO 4 ) 3 to a quasi-two-stage intercalation process that involves both Na+ and Zn 2+ . Initial charging of Na 3 V 2 (PO 4 ) 3 leads to a Na + -extracted phase corresponding to Na 3 V 2 (PO 4 ) 3 , whereas subsequent discharge results predominantly in Na + intercalation followed by Zn 2+ intercalation. Operando X-ray diffraction of Na 3 V 2 (PO 4 ) 3 was used to study the phase changes associated with the first charge/discharge process, and ex situ measurements were used to precisely link the changes in the crystal structure to a quasi-two-stage intercalation of Na + and Zn 2+ . The corresponding changes in the V-oxidation state, V-O coordination, and the presence of Zn 2+ were confirmed by X-ray absorption spectroscopy. The results of this work present a comprehensive understanding of the charge-storage properties for a well-established NASICON structure that confers both the high capacity (~100 mA h g -1 ) and high potential (1.35 and 1.1 V vs Zn/Zn 2+ ).

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

Chemical short-range order in derivative Cr–Ta–Ti–V–W high entropy alloys from the first-principles thermodynamic study

The development of high-entropy alloys (HEAs) focuses on exploring compositional regions in multi-component systems with all alloy elements in equal or near-equal atomic concentrations. Initially it was based on the main idea that high mixing configurational entropy contributions to the alloy free energy could promote the formation of a single solid solution phase. By using the ab-initio based Cluster Expansion (CE) Hamiltonian model constructed for the quinary bcc Cr–Ta–Ti–V–W system in combination with Monte Carlo (MC) simulations, we show that the phase stability and chemical short-range order (SRO) of the equiatomic quinary and five sub-quaternary systems, as well as their derivative alloys, can dramatically change the order–disorder transition temperatures (ODTT) as a function of alloy compositions. In particular, it has been found, that the equiatomic quaternary Ta–Ti–V–W and Cr–Ta–Ti–W alloys had the lowest order–disorder transition temperature (500 K) among all the analysed equiatomic compositions. In all investigated alloy systems, the strongest chemical ordering has been observed between Cr and V, which led to the conclusion that decreasing the concentration of either Cr or V might be beneficial in terms of decreasing the ODTT. It also predicts that increasing concentration of Ti significantly decreases the ODTT. Our analysis of chemical SRO as a function of alloy composition allows to understand the microstructure evolution of HEAs as a function of temperature in excellent agreement with available experimental observations. Importantly, our free energy of mixing and SRO calculations predict that the origin of precipitates formed by Cr- and V-rich in the sub-quaternary Cr–Ta–V–W system is driven by the thermodynamics. The modelling results are in an excellent agreement with experimental observation of Cr and V segregation in the W 0.38 Ta 0.36 Cr 0.15 V 0.11 alloy which in turns shows an exceptional radiation resistance.

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

Improved thermonuclear rate of 42 Ti( p , γ ) 43 V and its astrophysical implication in the rp process

Context. Accurate 42 Ti(p,γ) 43 V reaction rates are crucial for understanding the nucleosynthesis path of the rapid capture process (rp process) that occurs in X-ray bursts. Aims. We aim to improve the thermonuclear rates of 42 Ti(p,γ) 43 V based on more complete resonance information and a more accurate direct component, together with the recently released nuclear masses data. We also explore the impact of the newly obtained rates on the rp process. Methods. We reevaluated the reaction rate of 42 Ti(p,γ) 43 V by the sum of the isolated resonance contribution instead of the Hauser-Feshbach statistical model. We used a Monte Carlo method to derive the associated uncertainties of new rates. The nucleosynthesis simulations were performed via the NuGrid post-processing code ppn. Results. The new rates differ from previous estimations due to the use of a series of updated resonance parameters and a direct S factor. Compared with the previous results from the Hauser-Feshbach statistical model, which assumes compound nucleus 43 V with a sufficiently high-level density in the energy region of astrophysical interest, large differences exist over the entire temperature region of rp-process interest, up to two orders of magnitude. We consistently calculated the photodisintegration rate using our new nuclear masses via the detailed balance principle, and found the discrepancies among the different reverse rates are much larger than those for the forward rate, up to ten orders of magnitude at the temperature of 10 8 K. Using a trajectory with a peak temperature of 1.95×10 9 K, we performed the rp-process nucleosynthesis simulations to investigate the impact of the new rates. Our calculations show that the adoption of the new forward and reverse rates result in abundance variations for Sc and Ca of 128% and 49%, respectively, compared to the variations for the statistical model rates. On the other hand, the overall abundance pattern is not significantly affected. The results of using new rates also confirm that the rp-process path does not bypass the isotope 43 V. Conclusions. Our study found that the Hauser-Feshbach statistical model is inappropriate to the reaction rate evaluation for 42 Ti(p,γ) 43 V. The adoption of the new rates confirms that the reaction path of 42 Ti(p,γ) 43 V(p,γ) 44 Cr(β + ) 44 V is a key branch of the rp process in X-ray bursts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Properties of V-defect injectors in long wavelength GaN LEDs studied by near-field electro- and photoluminescence

The efficiency of multiple quantum well (QW) light emitting diodes (LEDs) to a large degree depends on uniformity of hole distribution between the QWs. Typically, transport between the QWs takes place via carrier capture into and thermionic emission out of the QWs. In InGaN/GaN QWs, the thermionic hole transport is hindered by the high quantum confinement and polarization barriers. To overcome this drawback, hole injection through semipolar QWs located at sidewalls of V-defects had been proposed. However, in the case of the V-defect injection, strong lateral emission variations take place. In this work, we explore the nature of these variations and the impact of the V-defects on the emission spectra and carrier dynamics. The study was performed by mapping electroluminescence (EL) and photoluminescence (PL) with a scanning near-field optical microscope in LEDs that contain a deeper well that can only be populated by holes through the V-defects. Applying different excitation schemes (electrical injection and optical excitation in the far- and near-field), we have shown that the EL intensity variations are caused by the lateral nonuniformity of the hole injection. We have also found that, in biased structures, the PL intensity and decay time in the V-defect regions are only moderately lower that in the V-defect-free regions thus showing no evidence of an efficient Shockley-–Read–Hall recombination. In the V-defect regions, the emission spectra experience a red shift and increased broadening, which suggests an increase of the In content and well width in the polar QWs close to the V-defects.

Electroluminescence↗
DOE OSTI2021

Numerical assessment of the new V-shape small-angle slot divertor on DIII-D

The small-angle slot (SAS) divertor of the DIII-D tokamak, and its upcoming upgrade, the V-shape small-angle slot (SAS-V) divertor, are numerically investigated using the SOLPS-ITER code package, including the effect of particle drifts, for a range of plasma density, heating power, strike point position in the slot, and for both magnetic field directions. The simulations show that the electron temperature near the strike point is reduced in SAS-V compared to SAS, for both magnetic field directions, such that SAS-V achieves divertor detachment at a lower value of the outboard mid-plane separatrix electron density. The detachment threshold is lower because the V-shape focuses recycling neutrals on the V-end, densifying and cooling the plasma in the slot. At sufficiently high density, the V-shape also reduces the radial gradient of the temperature profile at the target, which in turns reduces the radial electric field and the E x B drift velocities, further densifying and cooling the plasma in the slot and leading to detachment. The V-shape effect, however, is reduced for higher heating power. With more heating power, the detachment density increases, reducing the ionization mean free path of recycled neutrals, which therefore become less sensitive to target shape changes. Furthermore, this suggests that in a fusion reactor, where the heating power is high, optimization of the divertor target shape needs to be combined with other strategies to lower the detachment density, such as in-slot injection of low-Z impurities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Pure edge-dislocation half-loops in low-temperature Ga⁢N for V-defect formation

Lateral injection of carriers through semipolar crystallographic planes into c-plane QWs is one of the new frontiers in III-N light-emitting diodes (LEDs), especially for long wavelengths. Strategic use of V-defects has proven to be the most promising method for lateral injection, and creating optimal V-defect structure and density is an important research area for reducing forward voltage and increasing wall plug efficiency. Here, in this article, we present a novel method for forming V-defects in nominally unstressed low-temperature Ga⁢N through the generation of pure edge-dislocation half-loops. We present a detailed material science analysis of the loops via scattering-contrast electron microscopy. The loops have pure-edge character with Burgers vector 1/3 ⁢⟨$11\bar{2}0$⟩, and form in a sessile orientation on {$11\bar{2}0$} a-planes. The two arms of the loops are inclined such that the extra half-planes face down toward the growth substrate. The dislocation loops can be used to intentionally form V-defects through conditions of kinetically limited growth: these conditions also favor nucleation of V-defects at ∼100% of other threading dislocations in the Ga⁢N templates. Patterned sapphire substrates (PSS) are one of the most important substrates for III-N LED growth because of their superior light extraction. However, due to its low threading dislocation density, PSS have not been used extensively for V-defect LEDs. This work provides a pathway for improved control of V-defect formation and density on LEDs grown on sapphire with the goal of enabling uniform lateral injection in these V-defect engineered LEDs with low forward voltage, including PSS for high light extraction.

LEDs↗
DOE OSTI2023

Expression of V-nitrogenase and Fe-nitrogenase in Methanosarcina acetivorans is controlled by molybdenum, fixed nitrogen, and the expression of Mo-nitrogenase

ABSTRACT All nitrogen-fixing bacteria and archaea (diazotrophs) use molybdenum (Mo) nitrogenase to reduce dinitrogen (N 2 ) to ammonia, with some also containing vanadium (V) and iron-only (Fe) nitrogenases that lack Mo. Among diazotrophs, the regulation and usage of the alternative V-nitrogenase and Fe-nitrogenase in methanogens are largely unknown. Methanosarcina acetivorans contains nif , vnf , and anf gene clusters encoding putative Mo-nitrogenase, V-nitrogenase, and Fe-nitrogenase, respectively. This study investigated nitrogenase expression and growth by M. acetivorans in response to fixed nitrogen, Mo/V availability, and CRISPRi repression of the nif , vnf , and/or anf gene clusters. The availability of Mo and V significantly affected growth of M. acetivorans with N 2 but not with NH 4 Cl. M. acetivorans exhibited the fastest growth rate and highest cell yield during growth with N 2 in medium containing Mo, and the slowest growth in medium lacking Mo and V. qPCR analysis revealed the transcription of the nif operon is only moderately affected by depletion of fixed nitrogen and Mo, whereas vnf and anf transcription increased significantly when fixed nitrogen and Mo were depleted, with removal of Mo being key. Immunoblot analysis revealed Mo-nitrogenase is detected when fixed nitrogen is depleted regardless of Mo availability, while V-nitrogenase and Fe-nitrogenase are detected only in the absence of fixed nitrogen and Mo. CRISPRi repression studies revealed that V-nitrogenase and/or Fe-nitrogenase are required for Mo-independent diazotrophy, and unexpectedly that the expression of Mo-nitrogenase is also required. These results reveal that alternative nitrogenase production in M. acetivorans is tightly controlled and dependent on Mo-nitrogenase expression. IMPORTANCE Methanogens and closely related methanotrophs are the only archaea known or predicted to possess nitrogenase. Methanogens play critical roles in both the global biological nitrogen and carbon cycles. Moreover, methanogens are an ancient microbial lineage and nitrogenase likely originated in methanogens. An understanding of the usage and properties of nitrogenases in methanogens can provide new insight into the evolution of nitrogen fixation and aid in the development nitrogenase-based biotechnology. This study provides the first evidence that a methanogen can produce all three forms of nitrogenases, including simultaneously. The results reveal components of Mo-nitrogenase regulate or are needed to produce V-nitrogenase and Fe-nitrogenase in methanogens, a result not seen in bacteria. Overall, this study provides a foundation to understand the assembly, regulation, and activity of the alternative nitrogenases in methanogens.

Biotechnology & Applied Microbiology↗
DOE OSTI2024

$K^0_S$ meson production in inelastic p+p interactions at 31, 40 and 80 $\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$ beam momentum measured by NA61$/$SHINE at the CERN SPS

The yields of $K^0_S$ mesons have been measured in inelastic p+p interactions at incident projectile momenta of 31, 40 and 80 $\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$ ($\sqrt{s_{NN}}=7.7, 8.8$ and 12.3 $\text {Ge}\hspace{-1.00006pt}\text {V}$, respectively). The data were recorded by the NA61$/$SHINE spectrometer at the CERN Super Proton Synchrotron and the $K^0_S$ mesons identified via their decays into $\pi ^{+} \pi ^{-}$ pairs. Double-differential distributions are presented as function of transverse momentum and rapidity. The mean multiplicities of $K^0_S$ mesons were determined to be $(5.95 \pm 0.19 (stat) \pm 0.30 (sys)) \times 10^{-2}$ at 31 $\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$, $(7.61 \pm 0.13 (stat) \pm 0.43 (sys)) \times 10^{-2}$ at 40 $\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$ and $(11.58 \pm 0.12 (stat) \pm 0.55 (sys)) \times 10^{-2}$ at 80 $\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$. The results on $K^{0}_{S}$ production are compared with the production of charged kaons in corresponding reactions and with model calculations (Epos1.99, SMASH 2.0 and PHSD) as well as with published data from other experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Vanadium and Niobium MXenes—Bilayered V 2 O 5 Asymmetric Supercapacitors

MXenes offer high metallic conductivity and redox capacitance that are attractive for high-power, high-energy storage devices. However, they operate limitedly under high anodic potentials due to irreversible oxidation. Pairing them with oxides to design asymmetric supercapacitors may expand the voltage window and increase the energy storage capabilities. Hydrated lithium preintercalated bilayered V 2 O 5 ( δ-Li x V 2 O 5 ·nH 2 O) is attractive for aqueous energy storage due to its high Li capacity at high potentials; however, its poor cyclability remains a challenge. To overcome its limitations and achieve a wide voltage window and excellent cyclability, it is combined with V 2 C and Nb 4 C 3 MXenes. Asymmetric supercapacitors employing lithium intercalated V 2 C (Li-V 2 C) or tetramethylammonium intercalated Nb 4 C 3 (TMA-Nb 4 C 3 ) MXenes as the negative electrode, and a δ-Li x V 2 O 5 ·nH 2 O composite with carbon nanotubes as the positive electrode in 5 m LiCl electrolyte operate over wide voltage windows of 2 and 1.6 V, respectively. The latter shows remarkably high cyclability—capacitance retention of ≈95% after 10 000 cycles. Here, this work highlights the importance of selecting appropriate MXenes to achieve a wide voltage window and a long cycle life in combination with oxide anodes to demonstrate the potential of MXenes beyond Ti 3 C 2 in energy storage.

36 MATERIALS SCIENCE↗
DOE OSTI2020

High-throughput characterization of Ag–V–O nanostructured thin-film materials libraries for photoelectrochemical solar water splitting

Ag–V–O thin-film materials libraries, with both composition (Ag 22-77 V 23-78 O x ) and thickness (123–714 nm) gradients were fabricated using combinatorial reactive magnetron co-sputtering aiming on establishing relations between composition, structure, and functional properties. As-deposited libraries were annealed in air at 300 °C for 10 h. High-throughput characterization methods of composition, structure and functional properties were used to identify photoelectrochemically active regions. The phases AgV 6 O 15 , Ag 2 V 4 O 11 , AgVO 3 , and Ag 4 V 2 O 7 were observed throughout the composition gradient. The photoelectrochemical properties of Ag–V–O films are dependent on composition and morphology. An enhanced photocurrent density (~300–554 μA/cm 2 ) was obtained at 30 to 45 at.% Ag along the thickness gradient. Thin films of these compositions show a nanowire morphology, which is an important factor for the enhancement of photoelectrochemical performance. The photoelectrochemically active regions were further investigated by high-throughput synchrotron-X-ray diffraction and transmission electron microscopy (Ag 32 V 68 O x ) which confirmed the presence of Ag 2 V 4 O 11 as the dominating phase along with the minor phases AgV 6 O 15 and AgVO 3 . This enhanced photoactive region shows bandgap values of ~2.30 eV for the direct and ~1.87 eV for the indirect bandgap energies. Finally, the porous nanostructured films improve charge transport and are hence of interest for photoelectrochemical water splitting.

36 MATERIALS SCIENCE↗
DOE OSTI2023

High-resolution rovibrational spectroscopy of trans -formic acid in the v 1 OH stretching fundamental: Dark state coupling and evidence for charge delocalization dynamics

High-resolution infrared (IR) reduced-Doppler absorption spectra of jet-cooled gas phase trans-formic acid in the v 1 OH stretching fundamental region are reported for the first time, obtained by supersonically expanding trans- formic acid/Ar mixtures through a slit jet nozzle source and rotationally cooling to T rot ≈ 10.9(5) K, with ab- sorption signals recorded by high-resolution difference-frequency IR absorption spectroscopy. Two a/b-type rovibrational bands of comparable intensity, one ~10-fold weaker b-type band, and one ~6-fold weaker a-type band are observed, with vibrational band origins at 3570.493(5), 3566.793(5), 3560.032(9), and 3534.6869(2) cm –1 , respectively. Based on previous Raman jet spectroscopic work by Nejad and Sibert [A. Nejad, E.L. Sibert III, The Raman jet spectrum of trans-formic acid and its deuterated isotopologs: Combining theory and experi- ment to extend the vibrational database, J. Chem. Phys. 154(6) (2021) 064301.], these four rovibrational bands have been assigned to v 1 , (v 2 + v 7 ), (v 6 + 2v 7 + 2v 9 ), and 2v 3 , respectively. Specifically, two of the three upper dark states (2 1 7 1 (a') and 6 1 7 2 9 2 (a')) are close enough to the “bright” 1 1 (a') state to facilitate strong anharmonic resonance interactions, which results in intensity mixing into the two zero-order bands that would otherwise be “dark”. Furthermore, our high-resolution spectral analysis reveals that there are local rotational crossings be- tween these zero-order 1 1 and 2 1 7 1 states resulting in extra lines (i.e., some upper levels in the nominally v 1 band have majority zero-order 2 1 7 1 state character). This motivates development of a 3 coupled state (1 1 , 2 1 7 1 , and 6 1 7 2 9 2 ) picture to aid in the spectral analysis, which is able to match all 3 observed band origins and relative band intensities, as well as indicate the necessity of multistate (> 2) coupling. Though limited by range of J and Ka levels (J’ ≤ 9 and K a ’ ≤ 3) populated at supersonic jet temperatures, this work offers first precision spec- troscopic analysis of trans-formic acid in the v 1 OH stretch region, which should aid in assignment of the more complete yet highly congested room temperature FTIR spectra. Lastly, and in sharp contrast to the spectral complexity in the three predominantly b-type bands, the lone a-type 2v 3 rovibrational band at 3534.6869(2) cm –1 is well described by a simple, rigid asymmetric top Hamiltonian.

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

Impact of threading dislocations on the V-defect assisted lateral carrier injection and recombination in InGaN quantum well LEDs

The nonuniform hole distribution between InGaN quantum wells (QWs) of light emitting diodes (LEDs) has a negative impact on LED efficiency. The uniformity can be increased by using lateral hole injection through sidewalls of V-defects, which form at threading dislocations. However, the inherent coupling between the V-defects and dislocations might affect efficiency of the hole injection and nonradiative recombination. In this work, we have tested the possible impact of the dislocations on the injection and recombination by means of scanning near-field electroluminescence and photoluminescence spectroscopy on single green-emitting InGaN QW LEDs containing large (∼0.5 μm) V-defects. The measurements have not provided any evidence of a lower hole injection efficiency or enhanced nonradiative recombination at the dislocations located at the V-defect facets or their apexes. This shows that large V-defects are excellent volumetric injectors for long wavelength InGaN LEDs. Furthermore, it was established that V-defects are preferential hole injectors even in single quantum well devices. Compared to vertical injection, the V-defect injection allows lowering the operating voltage, which should contribute to an enhanced wall plug efficiency.

42 ENGINEERING↗