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DOE OSTI2023

Photoaging of phenolic secondary organic aerosol in the aqueous phase: evolution of chemical and optical properties and effects of oxidants

Abstract. While gas-phase reactions are well established to have significant impacts on the mass concentration, chemical composition, and optical properties of secondary organic aerosol (SOA), the aqueous-phase aging of SOA remains poorly understood. In this study, we performed a series of long-duration photochemical aging experiments to investigate the evolution of the composition and light absorption of the aqueous SOA (aqSOA) from guaiacyl acetone (GA), a semivolatile phenolic carbonyl that is common in biomass burning smoke. The aqSOA was produced from reactions of GA with hydroxyl radical (•OH-aqSOA) or a triplet excited state of organic carbon (3C∗-aqSOA) and was then photoaged in water under conditions that simulate sunlight exposure in northern California for up to 48 h. The effects of increasing aqueous-phase •OH or 3C∗ concentration on the photoaging of the aqSOA were also studied. High-resolution aerosol mass spectrometry (HR-AMS) and UV–Vis spectroscopy were utilized to characterize the composition and the light absorptivity of the aqSOA and to track their changes during aging. Compared to •OH-aqSOA, the 3C∗-aqSOA is produced more rapidly and shows less oxidation, a greater abundance of oligomers, and higher light absorption. Prolonged photoaging promotes fragmentation and the formation of more volatile and less light-absorbing products. More than half of the initial aqSOA mass is lost, and substantial photobleaching occurs after 10.5 h of prolonged aging under simulated sunlight illumination for 3C∗-aqSOA and 48 h for •OH-aqSOA. By performing positive matrix factorization (PMF) analysis of the combined HR-AMS and UV–Vis spectral data, we resolved three generations of aqSOA with distinctly different chemical and optical properties. The first-generation aqSOA shows significant oligomer formation and enhanced light absorption at 340–400 nm. The second-generation aqSOA is enriched in functionalized GA species and has the highest mass absorption coefficients in 300–500 nm, while the third-generation aqSOA contains more fragmented products and is the least light absorbing. These results suggest that intermediately aged phenolic aqSOA is more light absorbing than other generations, and that the light absorptivity of phenolic aqSOA results from a competition between brown carbon (BrC) formation and photobleaching, which is dependent on aging time. Although photoaging generally increases the oxidation of aqSOA, a slightly decreased O/C of the •OH-aqSOA is observed after 48 h of prolonged photoaging with additional •OH exposure. This is likely due to greater fragmentation and evaporation of highly oxidized compounds. Increased oxidant concentration accelerates the transformation of aqSOA and promotes the decay of BrC chromophores, leading to faster mass reduction and photobleaching. In addition, compared with •OH, photoaging by 3C∗ produces more low-volatility functionalized products, which counterbalances part of the aqSOA mass loss due to fragmentation and evaporation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Search for the NΔ resonance in the 𝛾𝑑 → 𝑑𝜋 +𝜋 − reaction

A dibaryon which is an object with baryon number B = 2 has been studied for a long time. Dyson and Xuong classified non-strangeness dibaryon states based on SU(6) symmetries in 1960?s. In the framework, the deuteron is classified as one of the sextet states of dibaryons. Although dibaryon have been an interesting subject of research for a long time, most of the experimental studies up to the early 2000?s were unsuccessful. The CELCIUS/WASA collaboration reported this state via the double-pionic fusion reaction (?= ! 3c0c0) in 2009. Thereafter, the WASA-at-COSY collaboration revealed properties of the isoscaler resonance state via the ?= ! 3c0c0 reaction in 2011. The dibaryon resonance state with isospin ? = 0 and spin ( = 3 thought to be a ?03 which was predicted by Dyson and Xuong at 2.35 GeV?22 with a configuration of ??. The reported mass and width of that state were 2?37 GeV?22 and 0?07 GeV?22, espectively. The mass was ?0?08 GeV?22 smaller than that of 2?, the width was narrower than that of single ?. This surprising result made dibaryon study come back into the limelight. ?12 is one of the dibaryon states classified by Dyson and Xuong with isospin ? = 1, spin ( = 2. This state can be regarded as an s-wave #? resonance. ?12 is an interesting state from the point of view of the possibilities of existence as an internal structure of ?03 and contribution to many-body effects in nuclei. Though there were some experimental clues and theoretical studies of this state, it was unclear whether the obtained experimental results represented a real resonance or not due to the difficulty of separation from kinematical effects. Very recently, the FOREST group at Tohoku University reported a photoproduced isovector dibaryon state at mass of 2.14 GeV?22 in the 3c0 invariant mass spectra of the W3 ! 3c0c0 reaction. The most probable ?% configuration was 2¸ although they didn?t exclude the possibility of ?% = 1¸ or 3?. They separated the dibaryon production process from conventional pion production process for the first time using angular distribution of deuteron. We investigated the W3 ! 3c¸c? reaction for study of a possible #? dibaryon state using a deuterium target at the Research Center for Electron Photon Science, Tohoku University, Japan. In the experiment, ?3 ? 1012 tagged photon beam at energies ranging from 0.8 to 1.1 GeV was impinged to the liquid deuterium target (?520 mg?cm2) and the charged particles in the final state: deuteron, c¸, and c?, were detected by a magnetic spectrometer with a large solid angle named NKS2. NKS2 had capabilities of reconstructing momentum of charged particles, multi-track analysis, and ??c separation. We performed two different analyses named 2-track analysis and 3-track analysis. The 2-track (3-track) analysis was for events in which two (three) particles of 3c¸c? in the final state, including deuteron, were detected by NKS2. In the 3-track and 2-track analysis, ?2000? ?15000 events were identified as the W3 ! 3c¸c? reaction events, respectively. The 2-track analysis with higher statistics was mainly used to derive the cross sections, and the 3-track analysis was used to check the consistency of the 2-track analysis. In this thesis, we have shown the total cross section, the differential cross sections of the W3 ! 3c¸c? reaction in the region of jC j ¡ 0?15 GeV2. This is the world?s first measurement of this reaction in this energy region. Dibaryon resonance structures were observed below the #? threshold in the differential cross section of the invariant mass of 3c?. The mass and width of the structure were consistent with these of ?12 measured by the W3 ! 3c0c0 reaction. The mechanism of the production process was discussed based on the angular distribution of emitted deuteron.

Toyama, Yuichi↗
DOE OSTI2026

Balancing moisture and oxygen can match the crystallization dynamics of inert halide perovskite processing

Understanding crystallization in ambient environments is essential for scaling the fabrication of halide perovskite solar cells. Antisolvent-free perovskite deposition offers improved compatibility with high-throughput processing but introduces distinct crystallization dynamics relative to the more ubiquitous use of antisolvents in lab-scale perovskite fabrication. These dynamics are driven by interactions between solutes, solvent and the deposition environment. Using in situ wide-angle X-ray scattering during spin-coating and annealing, we demonstrate how relative humidity (RH) and oxygen, can be tuned to drive polytype evolution during ambient crystallization of formamidinium lead iodide to match that of inert synthesis and achieve comparable film and device quality. In an inert (N 2 ) environment, we find that perovskite films follow a well-established 2H → 3C phase transformation with a short period of coexistence of the 4H and 6H phase during heating. During crystallization in dry air (RH 0%), the added presence of oxygen leads to the dominance of 4H intermediate for an extended duration, establishing a 2H → 4H → 3C pathway. Introducing low humidity (RH 10%) suppresses the 4H phase to a short-lived intermediate above 100 °C, facilitating a more direct transition to the desired 3C phase and almost replicating the crystallization behavior observed under inert conditions. Interestingly, films crystallized under RH 10% show a lower onset temperature for the perovskite 3C phase than under N 2 . At higher humidity (RH 40%), the strong interaction of oxygen and moisture with iodoplumbates appears to stabilize higher order polytypes (4H and 6H). Devices fabricated under RH 10% achieve higher efficiency and enhanced stability compared to those produced under inert atmosphere. These findings provide mechanistic insight into crystallization pathways in different environments and provide a framework to transfer processes from inert to ambient conditions. The results highlight the critical role of controlled humidity in tuning antisolvent-free perovskite crystallization for scalable processing.

Hossain, Maimur [Univ. of California, San Diego, C↗
DOE OSTI2025

Mg and native defects in cubic silicon carbide from first principles

The diffusion of Mg defects in 3C-SiC is studied using the density functional theory. Mg has the highest burn-in rate as a transmutant in 3C-SiC when it is placed in high-energy neutron irradiation environment of a fusion reactor. The presence and evolution of transmutant defects impact thermal and mechanical properties of this important structural material. This study is focused on understanding the structure, stability, and evolution of Mg defects and the interaction of Mg with native defects in 3C-SiC. Our calculations of diffusion coefficients for different Mg defects suggest that Mg is likely to diffuse faster in pristine 3C-SiC than in the damaged one, in agreement with earlier experimental observations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Attraction and Longevity of 2- and 3-Component Food Cone Lures for the Caribbean Fruit Fly, Anastrepha suspensa (Diptera: Tephritidae)

Abstract The Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), is a quarantine pest of Citrus spp. and a production pest of guava and other specialty fruits in Florida. Effective monitoring lures and traps are needed for early pest detection and timely initiation of control measures. As part of a continued effort to identify attractive synthetic lures for the Caribbean fruit fly, we conducted field tests in Homestead, Florida to compare the efficacy and longevity of commercial 2- and 3-component cone lures (2C [ammonium acetate and putrescine], 3C [ammonium acetate, putrescine, and trimethylamine]), the current standards used by regulatory agencies, versus the traditional liquid protein bait consisting of hydrolyzed torula yeast and borax as a positive control. Additional lures were also field-aged and periodically brought into the laboratory to quantify residual chemical contents. Traps baited with the torula yeast-borax mixture captured the highest mean number of A. suspensa, and traps baited with the commercial 2C lures captured more flies than the 3C lures. Traps baited with torula yeast-borax also captured the highest number of nontarget Diptera. Captures with all three treatments were significantly biased toward females. Attractiveness of the 2C lure began to drop after 6–8 wk, and the 3C lure after 5–6 wk. Overall, these data suggest that the 2C cone lure is more attractive to A. suspensa than the 3C cone lure under field conditions in south Florida, and that the 2C lures are attractive for up to 8 wk.

Entomology↗
DOE OSTI2026

Bypassing the yellow phase for extremely stable formamidinium lead iodide perovskite solar cells

INTRODUCTION Formamidinium lead iodide (FAPI) emerged as an ideal material for single-junction perovskite solar cells owing to its near optimal bandgap of 1.45 to 1.5 eV and outstanding thermal stability. However, the photoactive cubic α-phase (3C-FAPI) of FAPI is structurally unstable and undergoes a reconstructive phase transition to the nonperovskite yellow hexagonal δ-phase (2H-FAPI) at ambient temperature. The phase reconstruction from 3C-FAPI to 2H-FAPI could be prevented by alloying methylammonium (MA) or Cs or both at the A-site and Br at the halide site, but this limits long-term durability owing to phase segregation or materials instability. Addressing these challenges requires a rational design strategy to stabilize 3C-FAPI by restricting lattice reconstruction without compromising thermal stability. RATIONALE Two main strategies have emerged to improve the phase stability and film quality of FAPI. Here, the first is a lattice-templating approach, which enables the slow formation of perovskite but it eventually degrades through the formation of yellow phases. The second approach, which has been widely explored, involves additive engineering, using alkyl ammonium halide or mostly chloride-based additives, which provide better control over the crystallization route. However, the FAPI films fabricated using these additives are often alloyed and compromise long-term stability. Moreover, the exact role of Cl has been unclear and speculative, specifically when Cl-based additives are used. Even after using a high additive concentration, the incorporation of Cl in perovskite lattice is rare. RESULTS Guided by synergistic modeling and experimental studies, we developed a coadditive strategy using 15 mol % FACl and 0.5 mol % BA 2 PbI 4 perovskites in combination (where BA is butylammonium) to enable a highly oriented (100) Cl-doped FAPI film with exceptional durability. Synchrotron-based in situ wide-angle x-ray scattering revealed a favorable transition for the coadditive-treated FAPI (FAPI-CA) to the corner-sharing 3C black phase through a progressive transformation through the 2H, 4H, 6H, and 8H phases. Moreover, solid-state 35 Cl nuclear magnetic resonance (NMR) revealed Cl incorporation in the perovskite lattice and, as predicted by modeling, indicated that Cl plays a key role in altering the energetics of both the formation and degradation pathways. The Cl-doped perovskite can completely bypass the expected and energetically favorable degradation pathway via the yellow phase or the 2H-PbI 2 phase. Instead, it undergoes degradation only upon exposure to harsh conditions such as 15-sun illumination and 90°C through the energetically uphill 3R-PbI 2 phase path. A p-i-n device fabricated with FAPI-CA film demonstrated a power conversion efficiency (PCE) of 25.1% with an average of 24.1% (40 devices). The notable film stability translated to other devices and retained 98% of its initial PCE under open-circuit conditions at 85° ± 5°C for 1200 hours. CONCLUSION Our study highlights the decisive role of chloride in regulating both the formation and degradation pathways. This regulation is critical for creating a perovskite film with commercially relevant durability.

Garai, Rabindranath [Rice Univ., Houston, TX (Unit↗
DOE OSTI2022

Effect of Foot-and-Mouth Disease Virus 2B Viroporin on Expression and Extraction of Mammalian Cell Culture Produced Foot-and-Mouth Disease Virus-like Particles

To improve the production of foot-and-mouth disease (FMD) molecular vaccines, we sought to understand the effects of the FMD virus (FMDV) 2B viroporin in an experimental, plasmid-based, virus-like particle (VLP) vaccine. Inclusion of the FMDV viroporin 2B into the human Adenovirus 5 vectored FMD vaccine enhanced transgene expression despite independent 2B expression negatively affecting cell viability. Evaluating both wildtype 2B and mutants with disrupted viroporin activity, we confirmed that viroporin activity is detrimental to overall transgene expression when expressed independently. However, the incorporation of 2B into an FMD molecular vaccine construct containing a wildtype FMDV 3C protease, a viral encoded protease responsible for processing structural proteins, resulted in enhancement of transgene expression, validating previous observations. This benefit to transgene expression was negated when using the FMDV 3CL127P mutant, which has reduced processing of host cellular proteins, a reversion resulting from 2B viroporin activity. Inclusion of 2B into VLP production constructs also adversely impacted antigen extraction, a possible side effect of 2B-dependent rearrangement of cellular membranes. These results demonstrate that inclusion of 2B enhanced transgene expression when a wildtype 3C protease is present but was detrimental to transgene expression with the 3CL127P mutant. This has implications for future molecular FMD vaccine constructs, which may utilize mutant FMDV 3C proteases.

2B↗
DOE OSTI2026

Direct Determination of 3C/4H Silicon Carbide Heterophase Interfaces by Electron Ptychography

Silicon carbide is a technologically relevant material that can exist in various structural polymorphs, each with its own electronic properties. Through the controlled growth of abrupt interfaces between the polymorphs, systems with emergent properties arise from differences in local bonding and stacking sequences. Determining the structure of these interfaces provides important insights into predicting and ultimately controlling their properties. Here, in this study, we use multislice electron ptychography (MEP) to qualitatively and quantitatively analyze interfaces between 3C and 4H silicon carbide in three dimensions. Two distinct interfaces are investigated: a coherent interface between $(1\bar{1}1)$ (3C) and $(0001)$ (4H) , and an incoherent interface between $(1\bar{1}2)$ (3C) and $(1\bar{1}00)$ (4H) . At the coherent interface, MEP enables direct quantification of a sharp boundary with an inclined step, whereas at the incoherent interface, local atomic displacements are determined along dislocation cores. By quantifying the spatial distribution and atomic-scale structure of these interfaces in three dimensions, this study provides insight into the complexity of silicon carbide heteropolytype interfaces, paving the way for theoretical modeling and the development of design rules to achieve desired properties.

heterophase interface↗
DOE OSTI2024

How to Turn Jets into Cylinders near Supermassive Black Holes in 3D General Relativistic Magnetohydrodynamic Simulations

Abstract Accreting supermassive black holes (SMBHs) produce highly magnetized relativistic jets that tend to collimate gradually as they propagate outward. However, recent radio interferometric observations of the 3C 84 galaxy reveal a stunning, cylindrical jet already at several hundred SMBH gravitational radii,r≳ 350r g . We explore how such extreme collimation emerges via a suite of 3D general relativistic magnetohydrodynamic simulations. We consider an SMBH surrounded by a magnetized torus immersed in a constant-density ambient medium that starts at the edge of the SMBH sphere of influence, chosen to be much larger than the SMBH gravitational radius,r B = 10 3 r g . We find that radiatively inefficient accretion flows (e.g., M87) produce winds that collimate the jets into parabolas near the black hole. After the disk winds stop collimating the jets atr≲r B , they turn conical. Once outsider B , the jets run into the ambient medium and form backflows that collimate the jets into cylinders some distance beyondr B . Interestingly, for radiatively efficient accretion, as in 3C 84, the radiative cooling saps the energy out of the disk winds; at early times, they cannot efficiently collimate the jets, which skip the initial parabolic collimation stage, start out conical near the SMBH, and turn into cylinders already atr≃ 300r g , as observed in 3C 84. Over time, the jet power remains approximately constant, whereas the mass accretion rate increases; the winds grow in strength and start to collimate the jets, which become quasi-parabolic near the base, and the transition point to a nearly cylindrical jet profile moves outward while remaining insider B .

Astronomy & Astrophysics↗
DOE OSTI2021

Data Release Report for the Source Physics Experiment Phase II: Dry Alluvium Geology Experiments (DAG-1 through DAG-4), Nevada National Security Site

The Dry Alluvium Geology (DAG) project was Phase II of the Source Physics Experiment and consisted of a series of four chemical explosive tests conducted in the same source hole on the Nevada National Security Site. This hole is located at 37.1146°N and -116.0693°W, with a surface elevation of 1,285.2 meters (m) (4,216.5 feet [ft]) above sea level. The first test (DAG-1) was conducted on July 20, 2018, at 16:51:52.67838 Coordinated Universal Time (UTC). The explosive source for DAG-1 was nitromethane initiated by a small plastic-bonded explosive (PBX) charge, detonated at the depth of 385.0 m (1,263.2 ft) below ground surface. DAG-1 had a trinitrotoluene (TNT) equivalent yield of 0.908 metric tons (2,002 pounds [lbs]). DAG-2 was conducted on December 19, 2018, at 18:45:56.92115 UTC. This test was the largest in the series, with a TNT equivalent yield of 50.997 metric tons (112,429 lbs). The explosive source for DAG-2 was nitromethane initiated by a small PBX charge, detonated at the depth of 299.8 m (983.6 ft) below ground surface. DAG-3 was conducted on April 27, 2019, at 15:49:01.84183 UTC. The explosive source for this test was nitromethane initiated by a small PBX charge, detonated at the depth of 149.9 m (492.0 ft) below ground surface. DAG-3 had a TNT equivalent yield of 0.908 metric tons (2,002 lbs). The final DAG test (DAG-4) was conducted on June 22, 2019, at 21:06:19.87632 UTC. The explosive source for DAG-4 was nitromethane initiated by a small PBX charge, detonated at the depth of 51.6 m (169.3 ft) below ground surface. DAG-4 had a TNT equivalent yield of 10.357 metric tons (22,833 lbs). The four tests were recorded by an extensive set of instrumentation that included sensors both at near-field (less than 200 m) and far-field (200 m or greater) distances. The near-field instruments consisted of three-component (3C) accelerometers installed at various depths ranging from 51.6 to 385 m (169.3 to 1,263.1 ft) below ground surface in boreholes positioned around the source hole, and arrays of single-component and 3C accelerometers on the surface. The far-field network comprised a variety of seismic and acoustic sensors, including short-period geophones, broadband seismometers, and 3C accelerometers at distances of 200 m to 400 kilometers. In addition, the DAG-2, DAG-3, and DAG-4 explosions were recorded by a temporary array of 496 geophones arranged in a densely spaced grid pattern known as “Large N.” This report coincides with the release of these data for analysts and organizations that are not participants in this program. This report describes the four DAG tests and the various types of near-field, far-field, and other data that are available. Assembled data sets are accessible through: Incorporated Research Institutions for Seismology, Data Management Center 1408 NE 45th Street, Suite 201, Seattle, Washington 98105 USA. www.iris.washington.edu

58 GEOSCIENCES↗
DOE OSTI2020

Advanced electrolytes for fast-charging high-voltage lithium-ion batteries in wide-temperature range

LiNixMnyCo1-x-yO2 (NMC) cathode materials with Ni=0.8 have attracted great interest for application in high energy-density lithium (Li)-ion batteries (LIBs) because of their high specific capacities at high voltages. However, the practical application of Ni-rich NMC in LIBs under high charge voltages (e.g. 4.4 V and above) still faces big challenges due to the severe capacity fading, which is directly related to the instability of the cathode/electrolyte interface. In this work, we develop new localized high-concentration electrolytes (LHCEs) based on carbonate solvents, which are compatible with graphite (Gr) anode and have a high oxidation potential over 4.9 V vs. Li/Li+. The optimal LHCE enables the Gr||NMC811 cells with 2.8 mAh cm-2 cathode areal capacity loading to achieve an excellent cycling stability over 600 cycles with a capacity retention of 94.2 % under a charge cut-off voltage of 4.4 V at 25 ?C, good rate capabilities under fast charging or discharging up to 3C rate, and superior low-temperature discharge performance down to -30 ?C with a capacity retention of 85.6% at C/5 rate. The findings in this work shed light a very promising strategy to develop new electrolytes for practical high-energy LIBs with Ni-rich NMC cathodes.

Zhang, Xianhui↗
DOE OSTI2020

Experimental and quantum mechanical characterization of an oxygen-bridged plutonium(IV) dimer

We report the synthesis and characterization of K 4 {[PuCl 2 (NO 3 ) 3 ] 2 (μ 2 -O)}·H 2 O, which contains the first known μ 2 -oxo bridge between two Pu IV metal centers. Adding to its uniqueness is the Pu-(μ 2 -O) bond length of 2.04 Å, which is the shortest of other analogous compounds. The Pu-(μ 2 -O)-Pu bridge is characterized by the mixing of s -, d -, and p -orbitals from Pu with the p -orbitals of O; the 5 f -orbitals do not participate in bonding. Natural bond orbital analysis indicates that Pu and O interact through one 3c-2e σ Pu-O-Pu and two 3c-2e π Pu-O-Pu bonding orbitals and that the electron density is highly polarized on the μ 2 -O. Bond topology properties analysis indicates that the Pu-(μ 2 -O) bond shares both ionic and covalent character. Quantum mechanical calculations also show that the dimer has multiconfigurational ground states, where the nonet, septet, quintet, triplet, and singlet are close in energy. This work demonstrates the interplay between experimental and computational efforts that is required to understand the chemical bonding of Pu compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Experimental and modeling studies of PR and ND oxalate solubility to high ionic strengths: Insight into actinide(III) oxalates

Actinide oxalates are chemical compounds important to nuclear industry, ranging from actinide separation in waste reprocessing, to production of specialty actinides, and to disposal of high level nuclear waste (HLW) and spent nuclear fuel (SNF). In this study, the solubility constants for Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O by performing solubility experiments in HNO 3 and mixtures of HNO 3 and H 2 C 2 O 4 at 23.0 ± 0.2 °C have been determined. The targeted starting materials, Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O, were successfully synthesized at room temperature using PrCl 3 , NdCl 3 and oxalic acid as the source metrials. Then, we utilized the targeted solubility-controlling phases to conduct solubility measurements. There was no phase change over the entire periods of experiments, demonstrating that Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O were the solubility-controlling phases in our respective experiments. Based on our experimental data, we have developed a thermodynamic model for Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O in the mixtures of HNO 3 and H 2 C 2 O 4 to high ionic strengths. The model for Pr 2 (C 2 O 4 ) 3 •10H 2 O reproduces well the reported experimental data for Pu 2 (C 2 O 4 ) 3 •10H 2 O, which are not utilized for the model development, demonstrating that Pr(III) is an excellent analog for Pu(III). Similarly, the model for Nd 2 (C 2 O 4 ) 3 •10H 2 O reproduces the solubility of Am 2 (C 2 O 4 ) 3 •10H 2 O and Cm 2 (C 2 O 4 ) 3 •10H 2 O. The Pitzer model was used for the calculation of activity coefficients. Based on the published, well established model for dissociation constants for oxalic acid and stability constants for actinide-oxalate complexes [i.e., AmC 2 O 4 + , and Am(C 2 O 4 ) 2 - ] to high ionic strengths, we have obtained the solubility constants (log 10 K 0 ) for the following reactions at 25 °C, Pr 2 (C 2 O 4 ) 3 •10H 2 O ⇌ 2Pr 3+ + 3C 2 O 4 2- + 10H 2 O(l). Nd 2 (C 2 O 4 ) 3 •10H 2 O ⇌ 2Nd 3+ + 3C 2 O 4 2- + 10H 2 O(l). to be -30.82 ± 0.30 (2σ), and - 31.14 ± 0.35 (2σ), respectively. These values for can be directly applied to Pu 2 (C 2 O 4 ) 3 •10H 2 O, Am 2 (C 2 O 4 ) 3 •10H 2 O and Cm 2 (C 2 O 4 ) 3 •10H 2 O. The model established for actinide oxalates by this study provides the needed knowledge with regard to solubilities of actinide/REE oxalates at various ionic strengths, and is expected to find applications in many fields, including the geological disposal of nuclear waste and the mobility of REE under the surface conditions, as Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O can be regarded as the pure Pr and Nd end-members of deveroite, a recently discovered natural REE oxalate with the following stoichiometry, (Ce 1.01 Nd 0.33 La 0.32 Pr 0.11 Y 0.11 Sm 0.01 Pb 0.04 U 0.03 Th 0.01 Ca 0.04 ) 2.01 (C 2 O 4 ) 2.99 •9.99H 2 O. Regarding its importance in the geological disposal of nuclear waste, Am 2 (C 2 O 4 ) 3 •10H 2 O/Pu 2 (C 2 O 4 ) 3 •10H 2 O/Cm 2 (C 2 O 4 ) 3 •10H 2 O can be the source-term phase for actinides, as demonstrated by the instance in the disposal in clay/shale formations. This is exemplified by the stability of Am 2 (C 2 O 4 ) 3 •10H 2 O in comparison with Am(OH) 3 (am), Am(OH) 3 (s) and AmCO 3 (OH)(s) under the relevant geological repository conditions.

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

Convergent Protocols for Computing Protein–Ligand Interaction Energies Using Fragment-Based Quantum Chemistry

Fragment-based quantum chemistry methods offer a way to sidestep the steep nonlinear scaling of electronic structure calculations so that large molecular systems can be investigated using high-level methods. Here, we use fragmentation to compute protein–ligand interaction energies in systems with several thousand atoms, using a new software platform for managing fragment-based calculations that implements a screened many-body expansion. Convergence tests using a minimal-basis semiempirical method (HF-3c) indicate that two-body calculations, with single-residue fragments and simple hydrogen caps, are sufficient to reproduce interaction energies obtained using conventional supramolecular electronic structure calculations, to within 1 kcal/mol at about 1% of the computational cost. We also demonstrate that the HF-3c results are illustrative of trends obtained with density functional theory in basis sets up to augmented quadruple-ζ quality. Strategic deployment of fragmentation facilitates the use of converged biomolecular model systems alongside high-quality electronic structure methods and basis sets, bringing ab initio quantum chemistry to systems of hitherto unimaginable size. This will be useful for generation of high-quality training data for machine learning applications.

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

A structural analysis of ordered Cs3Sb films grown on single crystal graphene and silicon carbide substrates

Alkali antimonides are well established as high efficiency, low intrinsic emittance photocathodes for accelerators and photon detectors. However, conventionally grown alkali antimonide films are polycrystalline with surface disorder and roughness that can limit achievable beam brightness. Ordering the crystalline structure of alkali antimonides has the potential to deliver higher brightness electron beams by reducing surface disorder and enabling the engineering of material properties at the level of atomic layers. In this report, we demonstrate the growth of ordered Cs3Sb films on single crystal substrates 3C-SiC and graphene-coated 4H-SiC using pulsed laser deposition and conventional thermal evaporation growth techniques. The crystalline structures of the Cs3Sb films were examined using reflection high energy electron diffraction and x-ray diffraction diagnostics, while film thickness and roughness estimates were made using x-ray reflectivity. With these tools, we observed ordered domains in less than 10 nm thick films with quantum efficiencies greater than 1% at 530 nm. Moreover, we identify structural features such as Laue oscillations indicative of highly ordered films. We found that Cs3Sb films grew with flat, fiber-textured surfaces on 3C-SiC and with multiple ordered domains and sub-nanometer surface roughness on graphene-coated 4H-SiC under our growth conditions. We identify the crystallographic orientations of Cs3Sb grown on graphene-coated 4H-SiC substrates and discuss the significance of examining the crystal structure of these films for growing epitaxial heterostructures in future experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Epitaxial integration of superconducting nitrides with cubic GaN

Epitaxial combination of transition metal nitrides and group III-nitrides holds significant potential for novel device architectures, given their wide array of properties and similar lattice constants. However, the mixture of hexagonal and cubic crystals limits structural quality and has stymied development. This work will discuss the molecular beam epitaxy synthesis of metastable cubic GaN on 3C-SiC templates and its integration with cubic ZrN and NbN superconductors in single and multilayer heterostructures. The fully cubic nature of GaN and the epitaxial nature of all layers are confirmed via in situ and ex situ techniques. The electrical transport properties of transition metal nitrides on cubic GaN (001) are compared to those grown directly on 3C-SiC (001) and c-plane hexagonal GaN templates. The determination of a similar growth window for cubic wide-bandgap and superconducting metal nitrides creates a platform for new epitaxial device architectures and potential applications in metamaterials, quantum information science, and condensed matter physics.

Condensed matter physics↗
DOE OSTI2020

Laser writing of nitrogen-doped silicon carbide for biological modulation

Conducting or semiconducting materials embedded in insulating polymeric substrates can be useful in biointerface applications; however, attainment of this composite configuration by direct chemical processes is challenging. Laser-assisted synthesis has evolved as a fast and inexpensive technique to prepare various materials, but its utility in the construction of biophysical tools or biomedical devices is less explored. Here, we use laser writing to convert portions of polydimethylsiloxane (PDMS) into nitrogen-doped cubic silicon carbide (3C-SiC). The dense 3C-SiC surface layer is connected to the PDMS matrix via a spongy graphite layer, facilitating electrochemical and photoelectrochemical activity. We demonstrate the fabrication of arbitrary two-dimensional (2D) SiC-based patterns in PDMS and freestanding 3D constructs. To establish the functionality of the laser-produced composite, we apply it as flexible electrodes for pacing isolated hearts and as photoelectrodes for local peroxide delivery to smooth muscle sheets.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

STILGAR Seismic Array Data

Two three-component dense seismic arrays were deployed above an active limestone mine in Pleasant Gap, Pennsylvania; one in the fall and one in the spring of 2023. Each campaign lasted approximately four weeks and included 80 to 100 seismic stations with stations spaced between 100 and 400 meters apart. Each campaign also included several small dense seismic arrays. Two types of seismic stations were deployed including FairfieldNodal ZLand 3C All-in-One seismometers and Geospace 3C GS-ONE geophone paired with GSX3 and GSX4 dataloggers. This dataset includes ~ 4 TB of three-component continuously recorded seismic data in the miniseed format data from both campaigns as well as a readme file for the data structure.

58 GEOSCIENCES↗