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

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Multi-site reaction dynamics through multi-fragment density matrix embedding

The practical description of disordered chemical reactions, where the reactions involve multiple species at multiple sites, is presently a challenge using correlated electronic structure methods due to their high computational cost and steep scaling. Here, we describe the gradient theory of multi-fragment density matrix embedding theory, which potentially provides a minimal computational framework to model such processes at the correlated electron level. We present the derivation and implementation of the gradient theory, its validation on model systems and chemical reactions using density matrix embedding, and its application to a molecular dynamics simulation of proton transport in a small water cluster, a simple example of multi-site reaction dynamics.

Chemistry↗
DOE OSTI2023

Porting fragmentation methods to GPUs using an OpenMP API: Offloading the resolution-of-the-identity second-order Møller–Plesset perturbation method

Here, using an OpenMP Application Programming Interface, the resolution-of-the-identity second-order Møller–Plesset perturbation (RI-MP2) method has been off-loaded onto graphical processing units (GPUs), both as a standalone method in the GAMESS electronic structure program and as an electron correlation energy component in the effective fragment molecular orbital (EFMO) framework. First, a new scheme has been proposed to maximize data digestion on GPUs that subsequently linearizes data transfer from central processing units (CPUs) to GPUs. Second, the GAMESS Fortran code has been interfaced with GPU numerical libraries (e.g., NVIDIA cuBLAS and cuSOLVER) for efficient matrix operations (e.g., matrix multiplication, matrix decomposition, and matrix inversion). The standalone GPU RI-MP2 code shows an increasing speedup of up to 7.5× using one NVIDIA V100 GPU with one IBM 42-core P9 CPU for calculations on fullerenes of increasing size from 40 to 260 carbon atoms using the 6-31G(d)/cc-pVDZ-RI basis sets. A single Summit node with six V100s can compute the RI-MP2 correlation energy of a cluster of 175 water molecules using the correlation consistent basis sets cc-pVDZ/cc-pVDZ-RI containing 4375 atomic orbitals and 14 700 auxiliary basis functions in ~0.85 h. In the EFMO framework, the GPU RI-MP2 component shows near linear scaling for a large number of V100s when computing the energy of an 1800-atom mesoporous silica nanoparticle in a bath of 4000 water molecules. The parallel efficiencies of the GPU RI-MP2 component with 2304 and 4608 V100s are 98.0% and 96.1%, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Engineering of a synthetic antibody fragment for structural and functional studies of K+ channels

Engineered antibody fragments (Fabs) have made major impacts on structural biology research, particularly to aid structural determination of membrane proteins. Nonetheless, Fabs generated by traditional monoclonal technology suffer from challenges of routine production and storage. Starting from the known IgG paratopes of an antibody that binds to the “turret loop” of the KcsA K+ channel, we engineered a synthetic Fab (sFab) based upon the highly stable Herceptin Fab scaffold, which can be recombinantly expressed in Escherichia coli and purified with single-step affinity chromatography. This synthetic Fab was used as a crystallization chaperone to obtain crystals of the KcsA channel that diffracted to a resolution comparable to that from the parent Fab. Furthermore, we show that the turret loop can be grafted into the unrelated voltage-gated Kv1.2–Kv2.1 channel and still strongly bind the engineered sFab, in support of the loop grafting strategy. Macroscopic electrophysiology recordings show that the sFab affects the activation and conductance of the chimeric voltage-gated channel. These results suggest that straightforward engineering of antibodies using recombinant formats can facilitate the rapid and scalable production of Fabs as structural biology tools and functional probes. The impact of this approach is expanded significantly based on the potential portability of the turret loop to a myriad of other K+ channels.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

High intensity x-ray interaction with a model bio-molecule system: double-core-hole states and fragmentation of formamide

Formamide, a simple model bio-molecule (HCONH 2 ), is irradiated with high intensity, ultrashort pulses from an x-ray free electron laser. Ionic fragments resulting from photoionization and subsequent decay processes are recorded, as well as the electronic signature of the different inner shell ionization events that can take place during the x-ray pulses. Additionally, the formation of double-core-hole states, where a second inner shell electron is removed before the first core hole has been refilled is observed in the electron spectra, recorded at all three sites (C, N, O) of the molecule. The individual ionization potentials are compared with results of ab initio calculations at different level of theory. Based on our results, future opportunities for advanced studies of inner-shell-induced electronic and nuclear dynamics are explored.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2022

Coalescence, the thermal model and multi-fragmentation: the energy and volume dependence of light nuclei production in heavy ion collisions

Here, we present results of a phase space coalescence approach within the UrQMD transport and -hybrid model for a very wide range of beam energies from SIS to LHC. The coalescence model is able to qualitatively describe the whole range of experimental data with a fixed set of parameters. Some systematic deviations are observed for very low beam energies where the role of feed down from heavier nuclei and multi-fragmentation becomes relevant. The coalescence results are mostly very close to the thermal model fits. However, both the coalescence approach as well as thermal fits are struggling to simultaneously describe the triton multiplicities measured with the STAR and ALICE experiment. The double ratio of tp/d 2 , in the coalescence approach, is found to be essentially energy and centrality independent for collisions of heavy nuclei at beam energies of E lab > 10A GeV. On the other hand the clear scaling of the d/p 2 and t/p 3 ratios with the systems volume is broken for peripheral collisions, where a canonical treatment and finite size effects become more important.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

A CRISPR-Cas9–integrase complex generates precise DNA fragments for genome integration

CRISPR-Cas9 is an RNA-guided DNA endonuclease involved in bacterial adaptive immunity and widely repurposed for genome editing in human cells, animals and plants. In bacteria, RNA molecules that guide Cas9 s activity derive from foreign DNA fragments that are captured and integrated into the host CRISPR genomic locus by the Cas1-Cas2 CRISPR integrase. How cells generate the specific lengths of DNA required for integrase capture is a central unanswered question of type II-A CRISPR-based adaptive immunity. Here, we show that an integrase supercomplex comprising guide RNA and the proteins Cas1, Cas2, Csn2 and Cas9 generates precisely trimmed 30-base pair DNA molecules required for genome integration. The HNH active site of Cas9 catalyzes exonucleolytic DNA trimming by a mechanism that is independent of the guide RNA sequence. These results show that Cas9 possesses a distinct catalytic capacity for generating immunological memory in prokaryotes.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Discovery of 98 Sn Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 124 Xe Beam

We present the discovery of a new isotope of $^{98}$Sn beyond the double-magic N = Z = 50 nucleus $^{100}$Sn. $^{98}$Sn was identified among the projectile-fragmentation products of a $^{124}$Xe beam at 345 MeV/nucleon at the RI Beam Factory, RIKEN, Japan. Additionally, we have confirmed the production of $^{96}$In and $^{94}$Cd, previously reported as new isotopes at RIKEN. These highly proton-rich nuclei were separated and identified using the large-acceptance two-stage separator BigRIPS. Furthermore, we have determined the cross sections of $^{98}$Sn and its neighboring nuclei. These experimental values were compared to the semi-empirical cross-section formula EPAX3.1a, resulting in a reduction of the predicted cross sections by roughly a factor of 5.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2026

In-beam 𝛾-ray spectroscopy of 29 S populated in direct knockout, dissipative reactions, and fragmentation

Excited states in the neutron-deficient nucleus 29 S were populated in one-neutron knockout and several-nucleon removal reactions and studied using in-beam 𝛾-ray spectroscopy. New excited states and 𝛾-ray transitions were established using the Segmented Germanium Array SeGA and the 𝛾-ray tracking array GRETINA. The new transitions observed in the highly dissipative tail of the parallel momentum distribution from one-nucleon knockout and in five- and nine-nucleon removal reactions were utilized to calculate mirror energy differences with 29 Al . Highly dissipative reactions further prove to be a valuable tool in populating excited states typically inaccessible in direct reactions. The relative populations of the states in 29 S from the several-nucleon removal reactions were found to be consistent, suggesting for the first time that five-nucleon removal behaves predominately like statistical fragmentation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

New physics particles mixing with mesons: Production in the fragmentation chain

A class of extensions to the Standard Model adds hypothetical long-lived particles (LLPs) that have mass- or kinetic-mixing with neutral mesons, such as pions or rho mesons. The mixing can contribute significantly to the production of LLPs at proton accelerator experiments, and no consistent description of these production modes exists in the literature. In this paper, we develop a framework for studying different LLPs—dark photons, vector mediators coupled to the baryon current, and axionlike particles with different coupling patterns. In particular, we implement the production mechanisms in PYTHIA 8, study how the overall flux and kinematic distributions depend on the LLP’s mass, and compare various subprocesses where the mixing contributes—proton bremsstrahlung, meson decay, and production in the fragmentation chain. We find that our new description of LLP production predicts an integrated flux that differs from current approaches by one to two orders of magnitude, and highlight the unavoidable theoretical uncertainties coming from poor knowledge of the properties of heavy mesons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Beyond fragmented dopant dynamics in quantum spin lattices: Robust localization and non-Gaussian diffusion

The motion of dopants in magnetic spin lattices has received tremendous attention for at least four decades due to its connection to high-temperature superconductivity. Despite these efforts, we lack a complete understanding of their behavior, especially out of the equilibrium and at nonzero temperatures. In this paper, we take a significant step towards a much deeper understanding based on state-of-the-art matrix-product-state calculations. In particular, we investigate the nonequilibrium dynamics of a dopant in two-leg 𝑡−𝐽 ladders with antiferromagnetic XXZ spin interactions. In the Ising limit, we find that the dopant is localized for all investigated nonzero temperatures due to an emergent disordered potential, with a localization length controlled by the underlying correlation length of the spin lattice, which increases exponentially with decreasing temperature. The dopant, hereby, only delocalizes asymptotically in the zero temperature limit. This greatly generalizes the localization effect discovered recently in Hilbert space fragmented models [Phys. Rev. Res. 6, 023325 (2024), SciPost Phys. Core 7, 054 (2024)]. In the presence of spin-exchange processes at rate 𝛼, the dopant diffuses with a diffusion coefficient, 𝐷 ℎ , depending nonmonotonically on 𝛼. It initially increases linearly as 𝐷 ℎ ∝ 𝛼 for 𝛼 ≪ 1 before dropping off as 𝛼 −1 for 𝛼 > 1. Moreover, we show that the underlying spin dynamics at infinite temperature behaves qualitatively the same, albeit with important quantitative differences. We substantiate these findings by showing that the dynamics features self-similar scaling behavior, which strongly deviates from the Gaussian behavior of regular diffusion, especially for weak spin exchange. Finally, we show that the diffusion coefficient 𝐷 ℎ follows an Arrhenius relation at high temperatures, whereby it is exponentially suppressed upon cooling.

Anomalous diffusion↗
DOE OSTI2026

Comment on “QCD factorization with multihadron fragmentation functions”

We make several comments on the recent work in Rogers et al. [Phys. Rev. D 111, 056001 (2025)] while also reaffirming and adding to the work in Pitonyak et al. [Phys. Rev. Lett. 132, 011902 (2024)]. We show that the factorization formula for 𝑒 + ⁢𝑒 − → (ℎ 1 ⋯ ℎ 𝑛 )⁢𝑋 in Rogers et al. is equivalent to a version one can derive using the definition of a 𝑛-hadron fragmentation function (FF) introduced in Pitonyak et al.. In addition, we scrutinize how to generalize the number density definition of a single-hadron FF to a 𝑛-hadron FF, arguing that the definition given in Pitonyak et al. should be considered the standard one while the definition in Rogers et al. has no clear interpretation. We also emphasize that the evolution equations for dihadron FFs (DiFFs) in Pitonyak et al. have the same splitting functions as those for single-hadron FFs. Therefore, the DiFF (and 𝑛-hadron FF) definitions in Pitonyak et al. have a natural number density interpretation and, contrary to what is stated in Rogers et al., are consistent with collinear factorization using the standard hard factors and evolution kernels.

Pitonyak, D. [Lebanon Valley College, Annville, PA↗
DOE OSTI2020

Angle-dependent strong-field ionization and fragmentation of carbon dioxide measured using rotational wave packets

In this work, we experimentally study the angle-dependent single ionization of carbon dioxide (CO 2 ) by linearly and circularly polarized pulses. The angle dependence of the ionization probability by linearly polarized pulses extracted from time-domain measurements on an impulsively excited rotational wave packet is compared with data obtained from a direct angle-scan measurement. The results from the measurement with linear and circular polarization are consistent with the adiabatic ionization approximation. Further, we extend the time-domain method to extract the dependence of the asymptotic momentum distribution of fragment ions on the orientation of the molecular axis, and apply it to investigate dissociative double ionization of CO 2 . We show that such measurements can directly test the validity of the axial recoil approximation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Angular correlation between the fission fragment intrinsic spins

The generation of fission fragment (FF) spins and of their relative orbital angular momentum has been debated for more than six decades, and no consensus has been achieved so far. The interpretation of recent experimental results of Wilson et al., has been challenged by several recent theoretical studies, which are not in agreement with one another. According to the interpretation by Wilson et al., the FF spins emerge very long after scission occurrs. Randrup and Vogt, while agreeing that the FF spins are uncorrelated, conclude on the basis of a phenomenological model that these spins are uncorrelated already before scission. Bulgac et al., in a fully microscopic study demonstrate that the primordial FF spin final values are defined before the emission of prompt neutrons and statistical gammas and are strongly correlated with a relative angle between spins close to 2π/3, a result in full agreement with the present independent analysis. The prompt neutrons and statistical gammas carry a significant amount of angular momentum according to the study of Stetcu et al. which can lead to a decorrelation of the FF bandhead spins of the yrast lines measured by Wilson et al., and which also provides arguments why these measured spins are so different from the primordial FF spins evaluated by Bulgac et al.. Here, I show that the unexpected character of the angular correlation between the primordial FF intrinsic spins, recently evaluated by Bulgac et al., which favors FF intrinsic spins pointing predominantly in opposite directions, can be understood by using simple general phase space arguments. The observation by Wilson et al., that the FF spins are uncorrelated follows from both the results of the microscopic calculation of Bulgac et al., and the present analysis of the full correlated probability distribution of the FF spins together with the relative orbital angular momentum of the primordial FFs. These arguments may apply also to heavy-ion collisions and, since there is no use of specifics of the particle interactions, the present results might apply to atomic and molecular systems as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Coupled fission fragment angular momenta

Here, nuclear fission produces fragments whose spins are coupled to the relative angular motion via angular momentum conservation. It is shown how ensembles of such spins can readily be obtained by either direct microcanonical sampling or by sampling of the associated normal modes of rotation. The resulting distribution of the spin-spin opening angle is illustrated in various three- and two-dimensional scenarios and it is demonstrated how recent mutually conflicting model calculations can be well reproduced with different assumptions about the scission geometry.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Consideration of memory of spin and parity in the fissioning compound nucleus by applying the Hauser-Feshbach fission fragment decay model to photonuclear reactions

Prompt and β-delayed fission observables, such as the average number of prompt and delayed neutrons, the independent and cumulative fission product yields, and the prompt γ-ray energy spectra for the photonuclear reactions on 235,238 U and 239 Pu, are calculated with the Hauser-Feshbach fission fragment decay (HF 3 ⁢D) model and compared with available experimental data. Further, in the analysis of neutron-induced fission reactions to the case of photo-induced fission, an excellent reproduction of the delayed neutron yields supports a traditional assumption that the photo fission might be similar to the neutron-induced fission at the same excitation energies regardless of the spin and parity of the fissioning systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Realtime dynamics of hyperon spin correlations from string fragmentation in a deformed four-flavor Schwinger model

Self-polarizing weak decays of Λ -hyperons provide unique insight into the role of entanglement in the fragmentation of QCD strings through measurements of the spin correlations of Λ Λ ¯ pairs produced in collider experiments. The simplest quantum field theory representing the underlying parton dynamics is the four-flavor massive Schwinger model plus an effective spin-flip term, where the flavors are mapped to light (up or down) and heavy (strange) quarks and their spins. This construction provides a novel way to explore hyperon spin correlations in 1 + 1 dimensions. We investigate the evolution of these correlations for different string configurations that are sensitive to the rich structure of the model Hamiltonian. Published by the American Physical Society 2024

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Power-Law Entanglement and Hilbert Space Fragmentation in Nonreciprocal Quantum Circuits

Quantum circuits utilizing measurement to evolve a quantum wave function offer a new and rich playground to engineer unconventional entanglement dynamics. Here, in this work, we introduce a hybrid, nonreciprocal setup featuring a quantum circuit, whose updates are conditioned on the state of a classical dynamical agent. In our example the circuit is represented by a Majorana quantum chain controlled by a classical N-state Potts chain undergoing pair flips. The local orientation of the classical spins controls whether randomly drawn local measurements on the quantum chain are allowed or not. This imposes a dynamical kinetic constraint on the entanglement growth, described by the transfer matrix of an N-colored loop model. It yields an equivalent description of the circuit by an SU(N)-symmetric Temperley-Lieb Hamiltonian or by a kinetically constrained surface growth model for an N-component height field. For N = 2, we find a diffusive growth of the half-chain entanglement toward a stationary profile S(L) ~ L 1/2 for L sites. For N ≥ 3, the kinetic constraints impose Hilbert space fragmentation, yielding subdiffusive growth toward S(L) ~ L 0.57 . This showcases how the control by a classical dynamical agent can enrich the entanglement dynamics in quantum circuits, paving a route toward novel entanglement dynamics in nonreciprocal hybrid circuit architectures.

1-dimensional spin chains↗
DOE OSTI2024

Evaluation of Surface Crack Formation in Photovoltaic Backsheets Using Fragmentation and Finite Element Simulations

Backsheet cracking is among the most commonly observed degradation modes of photovoltaic modules in the field. Cracks can reduce the ability of backsheets to fulfill their functions, such as protection of the modules from the environment or electrical insulation. Here, this work presents an evaluation of the degradation and cracking propensity of two backsheets during accelerated IEC TS 62788-7-2 (International Electrotechnical Commission) aging under the A3 condition with a fragmentation test using a coextruded polyamide backsheet (AAA), and a laminated multilayer backsheet with a polyethylene terephthalate core and outer layer and ethylene vinyl acetate inner layer (PPE). Results show the surface embrittlement of the AAA outer layer during exposure. A longer time of exposure causes cracks to form at lower strains during stretching and creates deeper cracks. Accordingly, Young's modulus of the outer layer increases, as measured by cross-sectional nanoindentation. PPE exhibits cracking after exposure as well. While no similar increase of modulus or crack depth can be observed, the outer layer of PPE exhibits more obvious signs of erosion during exposure, including progressive morphological changes and thickness losses. A finite element model is developed to simulate surface crack formation, based on initially zero-thickness decohesion elements. Decohesion criteria define a critical stress, at which these elements grow, and cracks can begin to form. These criteria are obtained via parameter optimization by comparison between simulation and experiment. The model is used to interpret crack formation in both backsheets.

14 SOLAR ENERGY↗