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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Aromatic and aliphatic hydrocarbon hydroxylation via a formally Ni IV =O oxidant

The reaction of (NMe 4 ) 2 [Ni II (L Ph )(OAc)] (1[OAc], L Ph = 2,2',2''-nitrilo-tris-(N-phenylacetamide); OAc = acetate) with 3-chloroperoxybenzoic acid (m-CPBA) resulted in the formation of a self-hydroxylated Ni III -phenolate complex, 2, where one of the phenyl groups of L Ph underwent hydroxylation. 2 was characterised by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a previously characterised Ni II -phenolate complex, 3. We postulate that self-hydroxylation was mediated by a formally Ni IV =O oxidant, formed from the reaction of 1[OAc] with m-CPBA, which undergoes electrophilic aromatic substitution to yield 2. This is supported by an analysis of the kinetic and thermodynamic properties of the reaction of 1[OAc] with m-CPBA. Addition of exogenous hydrocarbon substrates intercepted the self-hydroxylation process, producing hydroxylated products, providing further support for the formally Ni IV =O entity. This study demonstrates that the reaction between Ni II salts and m-CPBA can lead to potent metal-based oxidants, in contrast to recent studies demonstrating carboxyl radical is a radical free-chain reaction initiator in Ni II /m-CPBA hydrocarbon oxidation catalysis.

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

Extension of frozen natural orbital approximation to open-shell references: Theory, implementation, and application to single-molecule magnets

Natural orbitals are often used to achieve a more compact representation of correlated wave-functions. Using natural orbitals computed as eigenstates of the virtual–virtual block of the state density matrix instead of the canonical Hartree–Fock orbitals results in smaller errors when the same fraction of virtual space is frozen. This strategy, termed frozen natural orbital (FNO) approach, is effective in reducing the cost of regular coupled-cluster (CC) calculations and some multistate methods, such as EOM-IP-CC (equation-of-motion CC for ionization potentials). This contribution extends the FNO approach to the EOM-SF-CC ansatz (EOM-CC with spin-flip). In contrast to EOM-IP-CCSD, EOM-SF-CCSD relies on high-spin open-shell references. Using FNOs computed for an open-shell reference leads to an erratic behavior of the EOM-SF-CC energies and properties due to an inconsistent truncation of the α and β orbital spaces. A general solution to problems arising in the EOM-CC calculations utilizing open-shell references, termed OSFNO (open-shell FNO), is proposed. Furthermore, by means of singular value decomposition (SVD) of the overlap matrix of the α and β orbitals, the OSFNO algorithm identifies the corresponding orbitals and determines virtual orbitals corresponding to the singly occupied space. This is followed by SVD of the singlet part of the state density matrix in the remaining virtual orbital subspace. The so-computed FNOs preserve the spin purity of the open-shell orbital subspace to the extent allowed by the original reference, thus facilitating a safe truncation of the virtual space. The performance of OSFNO is benchmarked for selected diradicals and triradicals.

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

A zeroth-order active-space frozen-orbital embedding scheme for multireference calculations

Multireference computations of large-scale chemical systems are typically limited by the computational cost of quantum chemistry methods. In this work, we develop a zeroth-order active space embedding theory [ASET(0)], a simple and automatic approach for embedding any multireference dynamical correlation method based on a frozen-orbital treatment of the environment. ASET(0) is combined with the second-order multireference driven similarity renormalization group and tested on several benchmark problems, including the excitation energy of 1-octene and bond-breaking in ethane and pentyldiazene. Finally, we apply ASET(0) to study the singlet–triplet gap of p-benzyne and 9,10-anthracyne diradicals adsorbed on a NaCl surface. Our results show that despite its simplicity, ASET(0) is a powerful and sufficiently accurate embedding scheme applicable when the coupling between the fragment and the environment is in the weak to medium regime.

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

Subsurface spectroscopy of heterogeneous materials using optical wavefront shaping

Plastic-bonded explosives and propellants consist of energetic molecular crystals embedded in a polymer matrix that also includes additives, such as taggants, plasticizers, grit, antioxidants, etc. Furthermore, this heterogeneous composition renders these materials optically opaque, limiting optical characterization techniques (e.g., Raman spectroscopy) to probing chemical reactions at the sur-face. However, many reactions of interest are believed to occur inside the material where current optical techniques can not probe. To address this challenge, we have developed a new optical technique that utilizes feedback assisted wavefront shaping (using spatial light modulators) to focus probe light inside a heterogeneous material, such that we can perform subsurface spectroscopy. Recently, we demonstrated this technique by monitoring subsurface photodegradation and thermal degradation of Eu-doped molecular crystals using both fluorescence and Raman spectroscopy. Based off these successes we are now looking into improvements to this technique to allow for greater time resolution, including replacing our spatial light modulators with fast digital mirror devices, using ns optical phase conjugation, and self-healing optical beams.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Calculation of spin–orbit couplings using RASCI spinless one-particle density matrices: Theory and applications

Here we present the formalism and implementation for calculations of spin–orbit couplings (SOCs) using the Breit–Pauli Hamiltonian and non-relativistic wave functions described by the restricted active space configuration interaction (RASCI) method with general excitation operators of spin-conserving spin-flipping, ionizing, and electron-attaching types. The implementation is based on the application of the Wigner–Eckart theorem within the spin space, which enables the calculation of the entire SOC matrix based on the explicit calculation of just one transition between the two spin multiplets. Numeric results for a diverse set of atoms and molecules highlight the importance of a balanced treatment of correlation and adequate basis sets and illustrate the overall robust performance of RASCI SOCs. The new implementation is a useful addition to the methodological toolkit for studying spin-forbidden processes and molecular magnetism.

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

Equation-of-motion coupled-cluster method with double electron-attaching operators: Theory, implementation, and benchmarks

We report a production-level implementation of the equation-of-motion (EOM) coupled-cluster (CC) method with double electron-attaching (DEA) EOM operators of 2 p and 3 p 1 h types, EOM-DEA-CCSD. This ansatz, suitable for treating electronic structure patterns that can be described as two-electrons-in-many orbitals, represents a useful addition to the EOM-CC family of methods. We analyze the performance of EOM-DEA-CCSD for energy differences and molecular properties. By considering reduced quantities, such as state and transition one-particle density matrices, we compare EOM-DEA-CCSD wave functions with wave functions computed by other EOM-CCSD methods. The benchmarks illustrate that EOM-DEA-CCSD is capable of treating diradicals, bond-breaking, and some types of conical intersections.

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

High-resolution infrared spectroscopy of supersonically cooled singlet carbenes: Bromomethylene (HCBr) in the CH stretch region

First high-resolution spectra of cold (~35 K) singlet bromomethylene HCBr in the CH stretching (v 1 ) region from 2770 to 2850 cm-1 are reported using near quantum shot-noise limited laser absorption methods in a slit jet supersonic discharge expansion source. Three rovibrational bands are identified at high S/N (20:1 - 40:1) and rotationally assigned to i) the CH stretch fundamental (v 1 ) band $\tilde{X}$(1,0,0) ← $\tilde{X}$ (0,0,0) and ii) vibrational hot bands ($\tilde{X}$(1,1,0) ← $\tilde{X}$(0,1,0) and $\tilde{X}$(1,0,1) ← $\tilde{X}$(0,0,1)) arising from vibrationally excited HCBr populated in the discharge with single quanta in either the H–C–Br bend (v 2 ) or C–Br stretch (v 3 ) modes. Precision rotational constants are reported for a total of six states, with an experimentally determined CH stretch vibrational frequency (2799.38 cm -1 ) in good agreement with previous low-resolution fluorescence studies. Detailed analysis of the fundamental v 1 band highlights the presence of perturbations in the $\tilde{X}$(1,0,0) level, which we tentatively attribute to arise from the nearby triplet state $\tilde{a}$(0,0,1) through spin-orbit interaction or the multiple quanta $\tilde{X}$(0,2,1) singlet state via c-type Coriolis coupling. Reduced-Doppler resolution (60 MHz) in the slit-jet IR spectrometer permits clear observation of nuclear spin hyperfine structure, with experimental line shapes well reproduced by nuclear quadrupole/spin-rotation coupling constants from microwave studies. Lastly, the a-type to b-type transition intensity ratio for the fundamental CH stretch band is notably larger than predicted by a bond-dipole model, which from high level ab initio quantum calculations (CCSD(T)/PVQZ) can be attributed to vibrationally induced “charge-sloshing” of electron density along the polar C–Br bond.

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

Plasma–liquid interactions in the presence of organic matter—A perspective

As investigations in the biomedical applications of plasma advance, a demand for describing safe and efficacious delivery of plasma is emerging. It is quite clear that not all plasmas are “equal” for all applications. This Perspective discusses limitations of the existing parameters used to define plasma in context of the need for the “right plasma” at the “right dose” for each “disease system.” The validity of results extrapolated from in vitro studies to preclinical and clinical applications is discussed. We make a case for studying the whole system as a single unit, in situ. Furthermore, we argue that while plasma-generated chemical species are the proposed key effectors in biological systems, the contribution of physical effectors (electric fields, surface charging, dielectric properties of target, changes in gap electric fields, etc.) must not be ignored.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Taming the virtual space for incremental full configuration interaction

Incremental full configuration interaction (iFCI) closely approximates the FCI limit with polynomial cost through a many-body expansion of the correlation energy, providing highly accurate total energies within a given basis set. To extend iFCI beyond previous basis set limitations, this work introduces a novel natural orbital (NO) screening approach, incremental NO full configuration interaction (iNO-FCI). By consideration of the importance of virtual orbital selection in the convergence of iFCI, iNO-FCI maximizes the consistency between orbitals selected for each correlated body. iNO-FCI employs a principle of cancellation of errors and ensures that the same set of virtual NOs is used for interdependent terms. Here, this strategy significantly reduces computational cost without compromising precision. Computational savings of up to 95% are demonstrated, allowing access to larger basis sets that were previously computationally prohibitive. iNO-FCI is herein introduced and benchmarked for several difficult test cases involving double-bond dissociation, biradical systems, conjugated π systems, and the spin gap of a Cu-based transition metal complex.

Correlation energy↗
DOE OSTI2022

Impact of Lanthanide Complexation and Temperature on the Chemical Reactivity of N,N,N',N'-tetraoctyl diglycolamide (TODGA) with the Dodecane Radical Cation

The impact of lanthanide (Ln) metal ion complexation and temperature on the chemical reactivity of N,N,N',N'-tetraoctyl diglycolamide (TODGA) with the dodecane radical cation (RH?+) has been measured by electron pulse radiolysis. Complexation of trivalent neodymium (Nd), gadolinium (Gd), and ytterbium (Yb) by TODGA yielded [Ln(TODGA)3(NO3)3] complexes that exhibited significantly increased reactivity (up to 9.3×) with the RH?+ radical cation, relative to the “free” ligand: k([Ln(TODGA)3(NO3)3] + RH?+) = (8.99 ± 0.93) × 1010, (2.88 ± 0.40) × 1010, and (1.53 ± 0.34) × 1010 M–1 s–1, for Nd(III), Gd(III), and Yb(III), respectively. The kinetic enhancement measured for both ligands exhibited a dependence on atomic number. Arrhenius parameters—specifically activation energies (Ea) and pre-exponential factors (A)—were determined for the reaction of “free” TODGA ligand with the RH?+ radical cation, giving: Ea(TODGA) = 17.43 ± 1.64 kJ mol–1, and A(TODGA) = (1.08 ± 0.02) × 1013 M–1 s–1. This draft manuscript has been prepared in fulfillment of Milestone M4FT-22IN030402024.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Cation Radical-Accelerated Nucleophilic Aromatic Substitution for Amination of Alkoxyarenes

Nucleophilic aromatic substitution (S N Ar) is a common method for arene functionalization; however, reactions of this type are typically limited to electron-deficient aromatic halides. Herein, we describe a mild, metal-free, cation-radical accelerated nucleophilic aromatic substitution (CRA-S N Ar) using a potent, highly oxidizing acridinium photoredox catalyst. Selective substitution of arene C–O bonds on a wide array of aryl ether substrates was shown with a variety of primary amine nucleophiles. Mechanistic evidence is also presented that supports the proposed CRA-S N Ar pathway.

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

Crosslinking and Gelation of Polymer Brushes and Free Polymer Chains in a Confined Space during Controlled Radical Polymerization-A Computer Simulation Study

The confinement effect on crosslinking and gelation during controlled/living copolymerization of a monovinyl and a divinyl monomer was studied by Monte Carlo computer simulation using the dynamic lattice liquid method. The simulated reactions took place in plane-parallel slits of various widths for various grafting densities (GDs) and various initial initiator/crosslinker ratios ([X] 0 /[Ini] 0 ). Monomers and crosslinkers were initially randomly distributed in the slit, but initiators were either anchored to one solid plane (polymer brushes) or randomly distributed (free chains). For brushes, the gel point (GP) depended on GD and [X] 0 /[Ini] 0 . The higher these parameters, the lower was the gel point. The gel point was also affected by the slit width. For free, nongrafted chains, the dependence of GP on slit width was negligible. For brushes, a nonuniform density of crosslinks was found, the highest density was close to the wall. This asymmetry was high at the gel point and decreased at higher conversions.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Viscosity-Controlled Thiol–Ene Reaction and Its Impact on Mechanical Response of Dynamic Networks

The impact of curing conditions on the final properties of thioester-thiol-based dynamic polymer networks was systematically investigated. Despite identical monomer and cross-linker compositions, networks synthesized in the absence of solvent exhibited significantly higher shear moduli and longer relaxation times compared to those cured in solvent. These differences arise from viscosity-controlled photoinitiated thiol–ene reactions, where reduced chain mobility under solvent-free conditions suppresses termination between two polymer radicals, leading to higher reaction conversion. Fourier Transform Infrared (FTIR) spectroscopy and solid-state NMR (ssNMR) spectroscopy confirmed a greater degree of “click” reaction completion in higher viscosity environments. Control experiments revealed that prolonged radical lifetimes and suppressed termination reactions under solvent-free curing conditions contribute to these variations. Here, this study highlights the crucial role of processing conditions in determining cross-link density and, consequently, the dynamic mechanical behavior of polymer networks. It demonstrates that, beyond polymer chemistry, dynamic cross-linker design, and phase separation, curing conditions serve as a key design parameter for tailoring material performance to specific applications.

polymers↗
DOE OSTI2020

General Method for Determining Redox Potentials without Electrolyte

A novel method to determine redox potentials without electrolyte is presented here. The method is based on a new ability to determine the dissociation constant, $K°_d$, for ion pairs formed between any radical anion and any inert electrolyte counterion. These dissociation constants can be used to determine relative shifts of redox potential as a function of electrolyte concentration, connecting referenced potentials determined with electrochemistry (with 0.1 M electrolyte) to electrolyte-free values. Pulse radiolysis created radical anions enabling determination of equilibrium constants for electron transfer between anions of donor and acceptor molecules as a function of electrolyte concentration in THF. The measurements determined “composite equilibrium constants”, $K_{eqC}$, which contain information about the dissociation constant for the electrolyte cations, X + , with the radical anions of both the donor, $K°_d$(D –• ,X + ) and the acceptor, $K°_d$(A –• ,X + ). Dissociation constants were obtained for a selection of radical anions with tetrabutylammonium (TBA + ). The electrolyte was found to shift the reduction potentials of small molecules 1-methylpyrene and trans-stilbene by close to +130 mV whereas oligo-fluorenes and polyfluorenes experienced shifts of only (+25 ± 6) mV due to charge delocalization weakening the ion pair. These shifts for reduction of aromatic hydrocarbon molecules are smaller than shifts of +232 and +451 mV seen previously for benzophenone radical anion with TBA + and Na + respectively where the charge on the radical anion is localized largely on one C=O bond, thus forming a more tightly bound ion pair.

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

Elucidating the modes of incorporation of the ferulic acid amides feruloyltyramine and feruloyloctopamine into the lignin-suberin fraction of potato periderms

Ferulic acid amides are naturally present in the cell walls of potato (Solanum tuberosum) periderms. In this study, we investigated their modes of incorporation into the periderm cell wall polymers. A lignin/suberin-enriched fraction was isolated and analyzed by GPC, DFRC, and 2D-NMR. The analyses revealed that the lignin domain of this fraction was predominantly composed of G-lignin units, with an H:G:S ratio of 2:70:28 (S/G ratio of 0.40). More importantly, the data also indicated the presence of two ferulic acid amides, feruloyltyramine and feruloyloctopamine, that are incorporated into the lignin/suberin structure of potato periderms through a variety of linkages, including 8-O-4' and 4-O-beta' ether linkages, as well as 8-5' linkages forming a phenylcoumaran structure involving the ferulate moiety. Although the phenolic groups of the tyramine and octopamine moieties could theoretically undergo oxidation, potentially creating additional sites for radical coupling, our research indicates that these groups remain predominantly as free phenolic entities that do not participate in radical coupling. On the other hand, all the phenolic groups of the ferulate moieties are bound through ether linkages reinforcing the conclusion that the feruloyltyramine and feruloyloctopamine moieties are linked to lignin/suberin within the cell wall via radical coupling reactions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Driving Force Dependent Photoinduced Charge Transfer Dynamics in Polymer-Wrapped Semiconducting Single-Walled Carbon Nanotubes

Here, we investigate the thermodynamic driving-force dependences of photoinduced charge separation (CS) and subsequent charge transfer dynamics in single-walled carbon nanotube (SWNT)–perylenediimide (PDI) donor–acceptor (D–A) superstructures. Pump–probe spectroscopy reveals that [SWNT (•+)n ]-(PDI –• ) n CS states form on an ∼100 fs time scale following photoexcitation; these dynamics are invariant across an ∼400 mV driving force range, indicating that SWNT hole polaron formation time scales are determined by nanotube lattice and solvent relaxation. These CS states feature SWNT hole polarons adjacent to (geminate) and nearby (nongeminate) PDI radical anions. Analysis of the free energy dependence for charge recombination (CR) of [SWNT •+ ] geminate -(PDI –• ) CS states highlights an ∼2 meV value for D–A electronic coupling (HAB) and ∼0.93 eV for the total reorganization energy (λ T ). A corresponding driving force dependence of the CR dynamics for [SWNT •+ ] nongeminate -(PDI –• ) CS states indicates a diminished H AB value (∼0.6 meV) and a larger λ T (∼1.1 eV), consistent with larger transfer distances. SWNT excitons that persist following photoinduced CS drive photooxidation of PDI –• components of [SWNT (•+)n ]-(PDI –• ) n CS states ( 1 SWNT* + PDI •– → PDI + SWNT •– ); this reaction manifests a significantly reduced λ T value (∼0.67 eV) as the initially prepared SWNT reduced state bears the character of a conduction band injected electron ([SWNT •– ] CB ). This reaction thus gives rise to relaxed, nongeminate SWNT electron and hole polarons on the same nanotube; these polarons react on a 10 2 ps time scale independent of the electronic structure of these SWNT-PDI superstructures.

anions↗
DOE OSTI2022

Calculated electron paramagnetic resonance g-tensor and hyperfine parameters for zinc vacancy and N related defects in ZnO

Various defects in ZnO, focused on substitutional N O and N 2 in various sites, O-site, interstitial and Zn-site are studied using first-principles calculations with the goal of understanding the electron paramagnetic resonance (EPR) center reported for N 2 in ZnO and substitutional N on the O-site. The g tensors are calculated using the gauge including projector augmented wave (GIPAW) method and compared with experiments. The g-tensor of the free $N^{+}_{2}$ and $N^{–}_{2}$ radicals and their various contributions within the GIPAW theory are analyzed first to provide a baseline reference for the accuracy of the method and for understanding the N 2 behavior in ZnO. Previous controversies on the site location of N 2 in ZnO for this EPR center and on the shallow or deep nature and donor or acceptor nature of this center are resolved. Here, we find that the N 2 on the Zn site is mostly zinc-vacancy like in its spin density and g-tensor, while for the O-site, a model with the N 2 axis lying in-the basal plane and the singly occupied π g -orbital along the c axis provides good agreement with experiment. For the interstitial location, if the N 2 is not strongly interacting with the surroundings, no levels in the gap are found and hence also no possible EPR center. The calculated g-tensors for N O and V Zn are also found to be in good agreement with experiment. The effects of different functionals affecting the localization of the spin density are shown to affect the g-tensor values.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Photochemical Ligand-Based CO 2 Reduction Mediated by Ruthenium Formyl Species

Here, a new, ligand-based strategy for CO 2 reduction to formate has been demonstrated. This approach relies on the photochemical generation of a coordinatively saturated transient ruthenium metalloformyl species, Ru-CHO, capable of reducing CO 2 to free formate directly. Under this paradigm, a highly reactive radical cation which is capable of facile formal hydrogen atom transfer (HAT) is generated via reductive quenching of an excited-state photosensitizer. Sequential electron transfer (ET) and HAT steps to a ruthenium carbonyl complex subsequently yield the Ru-CHO species, which upon further reduction undergoes fast hydride transfer to CO 2 , producing free formate. High formate selectivity (up to 98%) and impressive catalytic performance (TON ~5300; TOF ~0.1 s -1 ) was observed. Detailed mechanistic studies revealed that the overall process is highly sensitive to the identity of the radical cation, with divergent reactivity observed when HAT thermodynamics are altered. These findings provide new insights into ligand-based hydride transfer mechanisms and establish a foundation for the rational design of selective CO 2 reduction catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗