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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

The Singlet–Triplet Gap of Cyclobutadiene: The CIPSI-Driven CC( P ; Q ) Study

An accurate determination of singlet−triplet gaps in biradicals, including cyclobutadiene in the automerization barrier region where one has to balance the substantial nondynamical many-electron correlation effects characterizing the singlet ground state with the predominantly dynamical correlations of the lowest-energy triplet, remains a challenge for many quantum chemistry methods. High-level coupled-cluster (CC) approaches, such as the CC method with a full treatment of singly, doubly, and triply excited clusters (CCSDT), are often capable of providing reliable results, but routine application of such methods is hindered by their high computational costs. We have recently proposed a practical alternative to converging the CCSDT energetics at small fractions of the computational effort, even when electron correlations become stronger and connected triply excited clusters are larger and nonperturbative, by merging the CC(P;Q) moment expansions with the selected configuration interaction methodology abbreviated as CIPSI. We demonstrate that one can accurately approximate the highly accurate CCSDT potential surfaces characterizing the lowest singlet and triplet states of cyclobutadiene along the automerization coordinate and the gap between them using tiny fractions of triply excited cluster amplitudes identified with the help of relatively inexpensive CIPSI Hamiltonian diagonalizations.

Basis sets↗
DOE OSTI2024

Spectral broadening and vibronic dynamics of the S2 state of canthaxanthin in the orange carotenoid protein

We have performed a series of broadband multidimensional electronic spectroscopy experiments to probe the electronic and vibrational dynamics of the canthaxanthin chromophore of the Orange Carotenoid Protein (OCP) from Synechocystis sp. PCC 6803 in its photoactivated red state, OCPR. Cross-peaks observed below the diagonal of the two-dimensional electronic spectrum indicate that absorption transitions prepare the bright S2 state of the ketocarotenoid canthaxanthin near to a sequence of conical intersections, allowing passage to the dark S1 state via the Sx intermediate in <50 fs. Rapid damping of excited-state coherent wavepacket motions suggests that the branching coordinates of the conical intersections include out-of-plane deformation and C=C stretching coordinates of the π-conjugated isoprenoid backbone. The unusual proximity of the Franck–Condon S2 state structure to the conical intersections with Sx and S1 suggests that the protein surroundings of canthaxanthin prepare it to function as an excitation energy trap in the OCPR–phycobilisome complex. Numerical simulations using the multimode Brownian oscillator model demonstrate that the ground-state absorption spectrum of OCPR overlaps with the fluorescence emission spectrum of allophycocyanin due to spectral broadening derived especially from the intramolecular motions of the canthaxanthin chromophore in its binding site.

Yang, Kunwei↗
NASA NTRS1989

An active optimal control strategy of rotor vibrations using external forces

An active control strategy for lateral rotor vibrations using external forces is proposed. An extended state observer is used to reconstruct the full states and the unbalance distribution. An optimal controller which accommodates persistent unbalance excitation is derived with feedback of estimated states and unbalances. Numerical simulations were conducted for two separate four degree of freedom rotor systems. These simulations indicated that the proposed strategy can achieve almost complete vibration cancellation. This was shown to be true even when the number of external control forces was less than the system order so long as coordinate coupling was present. Both steady state and transient response at a constant speed are presented.

Zhu, W.↗
DOE OSTI2026

Coordinated Natural Gas and Electric Planning: Case Studies of Current Approaches and Practices

This paper examines how natural gas and electric utilities across eight U.S. states and two Canadian provinces are beginning to coordinate historically separate planning processes in response to growing system interdependencies, policy mandates, aging infrastructure, and changing customer energy choices. Electricity planning has long relied on robust integrated resource planning frameworks that weigh numerous objectives, risks, and costs. Natural gas planning, on the other hand, is typically less transparent and more narrowly focused on safety and system integrity. As economic, reliability, and policy drivers place new and shared demands on both systems, jurisdictions and utilities are experimenting with approaches such as coordinated forecasting, non pipeline alternatives, and combined planning pilots. A few have issued regulatory or statutory directives for greater data sharing and methodological alignment. Case studies from British Columbia, California, Colorado, Illinois, Massachusetts, Minnesota, New York, Québec, Rhode Island, and Washington illustrate a wide range of approaches to rethinking siloed planning. The paper identifies several common themes across the jurisdictions examined. It provides observations on the methods, processes, and organizational steps that may be needed in the future to address the challenges being faced by states and utilities. Lastly, it identifies some initial steps that states and utilities can consider if they would like to pursue more integrated, cost-effective, policy-aligned energy system planning.

03 NATURAL GAS↗
DOE OSTI2023

Molecular Switch Cobalt Redox Shuttle with a Tunable Hexadentate Ligand

Strong-field hexadentate ligands were synthesized and coordinated to cobalt metal centers to result in three new low-spin to low-spin Co(III/II) redox couples. The ligand backbone has been modified with dimethyl amine groups to result in redox potential tuning of the Co(III/II) redox couples from –200 to –430 mV versus Fc +/0 . The redox couples surprisingly undergo a reversible molecular switch rearrangement from five-coordinate Co(II) to six-coordinate Co(III) despite the ligands being hexadentate. The complexes exhibit modestly faster electron self-exchange rate constants of 2.2–4.2 M –1 s –1 compared to the high-spin to low-spin redox couple [Co(bpy) 3 ] 3 + /2 + at 0.27 M –1 s –1 , which is attributed to the change in spin state being somewhat offset by this coordination switching behavior. The complexes were utilized as redox shuttles in dye-sensitized solar cells with the near-IR AP25 + D35 dye system and exhibited improved photocurrents over the [Co(bpy) 3 ] 3 + /2 + redox shuttle (19.8 vs 18.0 mA/cm 2 ). Finally, future directions point toward pairing the low-spin to low-spin Co(II/III) tunable series to dyes with significantly more negative highest occupied molecular orbital potentials that absorb into the near-IR where outer sphere redox shuttles have failed to produce efficient dye regeneration.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Cloud-based Testbed for Adaptive Under-Frequency Load Shedding with High DER Penetration

Increasing penetration of distributed energy resources and behind-the-meter renewables may soon disrupt the efficacy of critical protection schemes, such as under-frequency load shedding (UFLS). Improved data exchange and coordination across the transmission-distribution boundary will be required to maintain reliability of bulk electric system. Standards-based data integration platforms using agreed-upon semantic vocabularies, such as the Common Information Model, will be key to enabling adaptive protection schemes requiring synthesized data from both the bulk power system and behind-the-meter resources. This paper introduces a cloud-based open-source data integration environment and UFLS clustering algorithm being developed to enable adaptive relay coordination between transmission and distribution utilities in the state of Vermont.

Anderson, Alexander A.↗
DOE OSTI2024

Ultrafast structural dynamics of UV photoexcited cis , cis -1,3-cyclooctadiene observed with time-resolved electron diffraction

Conjugated diene molecules are highly reactive upon photoexcitation and can relax through multiple reaction channels that depend on the position of the double bonds and the degree of molecular rigidity. Understanding the photoinduced dynamics of these molecules is crucial for establishing general rules governing the relaxation and product formation. Here, in this study, we investigate the femtosecond time-resolved photoinduced excited-state structural dynamics of cis,cis-1,3-cyclooctadiene, a large-flexible cyclic conjugated diene molecule, upon excitation with 200 nm using mega-electron-volt ultrafast electron diffraction and trajectory surface hopping dynamics simulations. We tracked the photoinduced structural changes from the Franck–Condon region through the conical intersection seam to the ground state. Our findings revealed a novel primary reaction coordinate involving ring distortion, where the ring stretches along one axis and compresses along the perpendicular axis. The nuclear wavepacket remains compact along this reaction coordinate until it reaches the conical intersection seam, and it rapidly spreads as it approaches the ground state, where multiple products are formed.

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

Metal–Ligand Based Mechanophores Enhance Both Mechanical Robustness and Electronic Performance of Polymer Semiconductors

The backbone of diketopyrrolopyrrole-thiophene-vinylene-thiophene-based polymer semiconductors (PSCs) is modified with pyridine (Py) or bipyridine ligands to complex Fe(II) metal centers, allowing the metal–ligand complexes to act as mechanophores and dynamically crosslink the polymer chains. Here, mono- and bi-dentate ligands are observed to exhibit different degrees of bond strengths, which subsequently affect the mechanical properties of these Wolf-type-II metallopolymers. The counter ion also plays a crucial role, as it is observed that Py-Fe mechanophores with non-coordinating BPh 4 – counter ions (Py-FeB) exhibit better thin film ductility with lower elastic modulus, as compared to the coordinating chloro ligands (Py-FeC). Interestingly, besides mechanical robustness, the electrical charge carrier mobility can also be enhanced concurrently when incorporating Py-FeB mechanophores in PSCs. This is a unique observation among stretchable PSCs, especially that most reports to date describe a decreased mobility when the stretchability is improved. Next, it is determined that improvements to both mobility and stretchability are correlated to the solid-state molecular ordering and dynamics of coordination bonds under strain, as elucidated via techniques of grazing-incidence X-ray diffraction and X-ray absorption spectroscopy techniques, respectively. This study provides a viable approach to enhance both the mechanical and the electronic performance of polymer-based soft devices.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Sources of error in heterodyne moire deflectometry

Alignment problems, and the accompanying errors, in heterodyne moire deflectometry are considered. A change in the x-directed offset between two states of a phase object causes a constant phase error, and it is noted that the relative x coordinate of the two photographic plates (the two states of the phase object) must be positioned typically within 1 micron to avoid a detectable offset. Possible solutions for assuring the relative alignment of the two deflectograms are considered, including a sandwich technique and a two-color double-exposure implementation.

Decker, Arthur J.↗
DOE OSTI2022

Electronic ground state of two nonmagnetic pentavalent honeycomb iridates

Here, we investigate the electronic structure of two Ir 5+ honeycomb iridates, Sr 3 CaIr 2 O 9 and NaIrO 3 , by means of resonant x-ray techniques. We confirm that Sr 3 CaIr 2 O 9 realizes a large spin-orbit driven nonmagnetic J eff =0 singlet ground state despite sizable tetragonal distortions of Ir coordinating octahedra. However, the resonant inelastic x-ray spectra of NaIrO 3 are drastically different from expectations for a Mott insulator with octahedrally coordinated Ir 5+ . We find that the data for NaIrO 3 can be best interpreted as originating from a narrow gap nonmagnetic S=0 band insulating ground state. Our results highlight the complex role of the ligand environment in the electronic structure of honeycomb iridates and the essential role of x-ray spectroscopy to characterize electronic ground states of insulating materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Spatiotemporal Studies of Soluble Inorganic Nanostructures with X‐rays and Neutrons

Abstract This Review addresses the use of X‐ray and neutron scattering as well as X‐ray absorption to describe how inorganic nanostructured materials assemble, evolve, and function in solution. We first provide an overview of techniques and instrumentation (both large user facilities and benchtop). We review recent studies of soluble inorganic nanostructure assembly, covering the disciplines of materials synthesis, processes in nature, nuclear materials, and the widely applicable fundamental processes of hydrophobic interactions and ion pairing. Reviewed studies cover size regimes and length scales ranging from sub‐Ångström (coordination chemistry and ion pairing) to several nanometers (molecular clusters, i.e. polyoxometalates, polyoxocations, and metal‐organic polyhedra), to the mesoscale (supramolecular assembly processes). Reviewed studies predominantly exploit 1) SAXS/WAXS/SANS (small‐ and wide‐angle X‐ray or neutron scattering), 2) PDF (pair‐distribution function analysis of X‐ray total scattering), and 3) XANES and EXAFS (X‐ray absorption near‐edge structure and extended X‐ray absorption fine structure, respectively). While the scattering techniques provide structural information, X‐ray absorption yields the oxidation state in addition to the local coordination. Our goal for this Review is to provide information and inspiration for the inorganic/materials science communities that may benefit from elucidating the role of solution speciation in natural and synthetic processes.

Yin, Jia‐Fu↗
DOE OSTI2025

Probing the Solvation Shells of Lithium Ions in Glyme-Based Electrolytes

Glymes have been extensively studied as solvents for Li-battery electrolytes, most recently in equimolar mixtures with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), due to their ability to form stable solvates. However, directly quantifying free and coordinated glyme molecules in the liquid state has been challenging due to several experimental limitations. Here, in this work, new vibrational probes are demonstrated for studying the solvation structures of diglyme and triglyme in LiTFSI electrolytes. These IR probes make use of an amine group to report the solvation state of glymes at salt-to-solvent molar ratios ranging from 1:5 to 1:10. Characterization of the thermodynamic properties of the solvent exchange occurring in the first solvation shell of lithium ions (Li + ) showed an equilibrium constant for these probes close to unity at room temperature. This result demonstrates that the probes exhibit a similar solvation behavior to their glyme analogue. Concentration dependence studies also revealed a lack of significant amounts of contact ion pairs at the studied concentrations. Moreover, the first solvation shell of Li + appears to be formed by two partially chelating glyme molecules, establishing that even triglyme with multiple chelation sites does not fully coordinate the cation. Complementary molecular dynamics (MD) simulations agree with the experimental results and suggest that at these concentrations, TFSI – predominantly forms solvent-separated ion pairs. However, the simulations do not properly capture the partial solvation structure of the glyme molecules in the solvation shell of Li + as derived from the experiments.

electrolytes↗
DOE OSTI2020

Controlling the Reduction of Chelated Uranyl to Stable Tetravalent Uranium Coordination Complexes in Aqueous Solution

The solution-state interactions between octadentate hydroxypyridinone (HOPO) and catecholamide (CAM) chelating ligands and uranium were investigated and characterized by UV-visible spectrophotometry and X-ray absorption spectroscopy (XAS), as well as electrochemically via spectroelectrochemistry (SEC) and cyclic voltammetry (CV) measurements. Depending on the selected chelator, we demonstrate the controlled ability to bind and stabilize U IV , generating with 3,4,3-LI(1,2-HOPO), a tetravalent uranium complex that is practically inert toward oxidation or hydrolysis in acidic, aqueous solution. At physiological pH values, we are also able to bind and stabilize U IV to a lesser extent, as evidenced by the mix of U IV and U VI complexes observed via XAS. Finally, CV and SEC measurements confirmed that the U IV complex formed with 3,4,3-LI(1,2-HOPO) is redox inert in acidic media, and U VI ions can be reduced, likely proceeding via a two-electron reduction process.

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

Spatiotemporal Studies of Soluble Inorganic Nanostructures with X‐rays and Neutrons

This Review addresses the use of X-ray and neutron scattering as well as X-ray absorption to describe how inorganic nanostructured materials assemble, evolve, and function in solution. We first provide an overview of techniques and instrumentation (both large user facilities and benchtop). We review recent studies of soluble inorganic nanostructure assembly, covering the disciplines of materials synthesis, processes in nature, nuclear materials, and the widely applicable fundamental processes of hydrophobic interactions and ion pairing. Reviewed studies cover size regimes and length scales ranging from sub-Ångström (coordination chemistry and ion pairing) to several nanometers (molecular clusters, i.e. polyoxometalates, polyoxocations, and metal-organic polyhedra), to the mesoscale (supramolecular assembly processes). Reviewed studies predominantly exploit 1) SAXS/WAXS/SANS (small- and wide-angle X-ray or neutron scattering), 2) PDF (pair-distribution function analysis of X-ray total scattering), and 3) XANES and EXAFS (X-ray absorption near-edge structure and extended X-ray absorption fine structure, respectively). While the scattering techniques provide structural information, X-ray absorption yields the oxidation state in addition to the local coordination. Our goal for this Review is to provide information and inspiration for the inorganic/materials science communities that may benefit from elucidating the role of solution speciation in natural and synthetic processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Optimizing fictitious states for Bell inequality violation in bipartite qubit systems with applications to the t t ¯ system

There is a significant interest in testing quantum entanglement and Bell inequality violation in high-energy experiments. Since the analyses in high-energy experiments are performed with events statistically averaged over phase space, the states used to determine observables depend on the choice of coordinates through an event-dependent basis and are thus not genuine quantum states, but rather “fictitious states.” We find that the basis which diagonalizes the spin-spin correlations is optimal for constructing fictitious states to test the violation of Bell’s inequality. This result is applied directly to the bipartite qubit system of a top and antitop produced at a hadron collider. We show that the beam axis is the optimal basis choice near the t t ¯ threshold production for measuring Bell inequality violation, while at high transverse momentum the basis that aligns along the momentum direction of the top is optimal. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2026

Assessing heat resilience coordination in networks of plans

Networks of plans coordinating on hazard mitigation can limit losses. We offer a novel network analysis methodology to investigate how networks of plans explicitly coordinate, and the purpose and nature of coordination. We illustrate the method using networks of plans shaping heat resilience in seven Arizona cities. The network analysis can help planners to identify influential plans that need to be high quality, peripheral plans, and potential governance silos. Furthermore, investigation into plan roles offers an ontological lens into how plans network, consult, and share information. The nature of coordination varies by purpose. General plans are cited for goals, while hazard mitigation plans are referenced for heat fact base. Transportation plans cite goals and fact base in other transportation plans, but rarely cite other plan types. Furthermore, these findings will help planners to consider the roles and merits of different plans while integrating hazards across the next generation of networks of plans.

coordination↗
NASA NTRS1992

Doubly excited 3P(e) resonant states in Ps(-)

Doubly excited 3P(e) resonant states in Ps(-) are calculated using a method of complex-coordinate rotation. Resonance parameters (both resonance positions and widths) for doubly excited states associated with the n = 2, 3, 4, 5, and 6 thresholds of positronium atoms are evaluated using elaborate Hylleraas-type functions. In addition to ten Feshbach-type resonances lying below various Ps thresholds, three shape resonances were identified, one each lying above the n = 2, 4, and 6 Ps thresholds. It is further noted that the energy levels for the present 3P(e) states are nearly degenerate with respect to the previously calculated 1P(0) states. Such a symmetric character suggests that the highly and doubly excited Ps(-), similar to its counterpart in H(-), would exhibit rovibrational behaviors analogous to those of XYX triatomic molecules.

Ho, Y. K.↗