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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Structural Analysis of K 4 Fe(CN) 6 ·3H 2 O, K 3 Fe(CN) 6 and Prussian Blue

XRD and XAS were used to characterize the bulk structure, while XPS was used to characterize the surface structure, of commercially obtained nominally K 4 Fe(CN) 6 ·3H 2 O, K 3 Fe(CN) 6 and our synthesized Prussian Blue (PB) material. K 4 Fe(CN) 6 ·3H 2 O was found to consist of a fully hydrated phase, which crystallizes in the monoclinic form and a less hydrated or anhydrous phase which crystallizes in the orthorhombic form. K 3 Fe(CN) 6 was found to consist of the well-established orthorhombic form rather than the monoclinic form. The structure of our synthesized Prussian Blue (PB) was found to be consistent with that reported for (KOH) 0.7 Fe(III) 1.33 Fe(II)(CN) 6 ·4.0H 2 O which crystallizes in the cubic form. XPS and XAS confirmed the presence of ferrous Fe(II) at the surface and bulk levels in K 4 Fe(CN) 6 ·xH 2 O. However, XPS revealed the presence of Fe(II) (~30%) and Fe(III) (~70%) in the surface region of K 3 Fe(CN) 6 while XAS confirmed the presence of mostly Fe(III) at the bulk level. Both XPS and XANES confirmed the presence of Fe(II) and Fe(III) in the surface and bulk regions of PB. We report that this ex situ XAS study will be used to support the analysis of an in situ XAS data collected on a PB containing supercapacitor to understand the mechanistic origin of pseudocapacitance in these devices.

42 ENGINEERING↗
DOE OSTI2023

Stabilization Of The CN 3 5− Anion In Recoverable High‐pressure Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates

Abstract A series of isostructural Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high‐pressure (25–54 GPa) high‐temperature (2000–3000 K) conditions in laser‐heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single‐crystal X‐ray diffraction (SCXRD) as well as corroborated by X‐ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln 3 O 2 (CN 3 ) solids are composed of the hitherto unknown CN 3 5− guanidinate anion—deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln 3 O 2 (CN 3 ) compounds are recoverable to ambient conditions. The stabilization of the CN 3 5− guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry.

Chemistry↗
DOE OSTI2022

Photodissociation Dynamics of Astrophysically Relevant Propyl Derivatives (C 3 H 7 X; X = CN, OH, HCO) at 157 nm Exploiting an Ultracompact Velocity Map Imaging Spectrometer: The (Iso)Propyl Channel

The photodissociation dynamics of astrophysically relevant propyl derivatives (C 3 H 7 X; X = CN, OH, HCO) at 157 nm exploiting an ultracompact velocity map imaging (UVMIS) setup has been reported. The successful operation of UVMIS allowed the exploration of the 157 nm photo dissociation of six (iso)propyl systems - n/i-propyl cyanide (C 3 H 7 CN), n/i-propyl alcohol (C 3 H 7 OH), and (iso)butanal (C 3 H 7 CHO) – to explore the C 3 H 7 loss channel. The distinct center-of-mass translational energy distributions for the i-C 3 H 7 X (X= CN, OH, HCO) could be explained through preferential excitation of the low frequency C-H bending modes of the formyl moiety compared to the higher frequency stretchings of the cyano and hydroxy moieties. Although the ionization energy of the n-C 3 H 7 radical exceeds the energy of a 157 nm photon, C 3 H 7 + was observed in the n-C 3 H 7 X (X= CN, OH, HCO) systems as a result of photoionization of vibrationally "hot" n-C 3 H 7 fragments, photoionization of i-C 3 H 7 after a hydrogen shift in vibrationally "hot" n-C 3 H 7 radicals, and/or two-photon ionization. Our experiments reveal that at least the isopropyl radical (i-C 3 H 7 ) and possibly the normal propyl radical (n-C 3 H 7 ) should be present in the interstellar medium and hence searched for by radio telescopes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

A shock-tube determination of the CN ground state dissociation energy and electronic transition moments for the CN violet and red band systems

The CN ground state dissociation energy and the sum of squares of the electronic transition moments of the CN violet bands have been simultaneously determined from spectral emission measurements behind incident shock waves. The unshocked test gases were composed of various CO2-CO-N2-Ar mixtures, and the temperatures behind the incident shocks ranged from 3500 to 8000 K. The variation of the electronic transition moment with internuclear separation was found to be small for both the CN violet and red band systems.

Arnold, J. O.↗
NASA NTRS1989

A high level Ab initio study of the anionic hydrogen-bonded complexes FH-CN-, FH-NC-, H2O-CN- and H2O-NC-

HF, H2O, CN- and their hydrogen-bonded complexes were studied using state-of-the-art ab initio quantum mechanical methods. A large Gaussian one particle basis set consisting of triple zeta plus double polarization plus diffuse s and p functions (TZ2P + diffuse) was used. The theoretical methods employed include self consistent field, second order Moller-Plesset perturbation theory, singles and doubles configuration interaction theory and the singles and doubles coupled cluster approach. The FH-CN- and FH-NC- and H2O-CN-, H2O-NC- pairs of complexes are found to be essentially isoenergetic. The first pair of complexes are predicted to be bound by approx. 24 kcal/mole and the latter pair bound by approximately 15 kcal/mole. The ab initio binding energies are in good agreement with the experimental values. The two being shorter than the analogous C-N hydrogen bond. The infrared (IR) spectra of the two pairs of complexes are also very similar, though a severe perturbation of the potential energy surface by proton exchange means that the accurate prediction of the band center of the most intense IR mode requires a high level of electronic structure theory as well as a complete treatment of anharmonic effects. The bonding of anionic hydrogen-bonded complexes is discussed and contrasted with that of neutral hydrogen-bonded complexes.

Lee, Timothy J.↗
NASA NTRS1989

A high-level ab initio study of the anionic hydrogen-bonded complexes FH-CN(-), FH-NC(-), H2O-CN(-), and H2O-NC(-)

HF, H2O, CN- and their hydrogen-bonded complexes were studied using state-of-the-art ab initio quantum mechanical methods. A large Gaussian one particle basis set consisting of triple zeta plus double polarization plus diffuse s and p functions (TZ2P + diffuse) was used. The theoretical methods employed include self consistent field, second order Moller-Plesset perturbation theory, singles and doubles configuration interaction theory and the singles and doubles coupled cluster approach. The FH-CN- and FH-NC- and H2O-CN-, H2O-NC- pairs of complexes are found to be essentially isoenergetic. The first pair of complexes are predicted to be bound by approx. 24 kcal/mole and the latter pair bound by approximately 15 kcal/mole. The ab initio binding energies are in good agreement with the experimental values. The two being shorter than the analogous C-N hydrogen bond. The infrared (IR) spectra of the two pairs of complexes are also very similar, though a severe perturbation of the potential energy surface by proton exchange means that the accurate prediction of the band center of the most intense IR mode requires a high level of electronic structure theory as well as a complete treatment of anharmonic effects. The bonding of anionic hydrogen-bonded complexes is discussed and contrasted with that of neutral hydrogen-bonded complexes.

Lee, Timothy J.↗
NASA NTRS1990

Simultaneous imaging of optical CN lines and radio HCN lines in comet Austin

The parent molecule of cometary CN has been the subject of speculation for a long time. When HCN was detected at 3.4 mm in Comet Kohoutek, the problem seemed to be resolved, but much more detailed work on Comet Halley raised the quantitative question of whether HCN could be the only parent. Therefore, comparative CN/HCN studies are vital for understanding the origin of cometary CN. The striking observation of CN jets in Comet Halley raised another very interesting question about the origin of CN. Traditional theory permits only dust features to remain well defined far from the nucleus. The CN jets were interpreted as arising from submicron sized dust particles, perhaps CHON particles. An estimated 10 to 50 percent of the CN in the comet was in the jets in the Halley observations. Several hypotheses can be made: (1) some of the CN originates from the dust and has nothing to do with HCN; or, (2) at least some of the HCN is also produced from the dust in the coma rather than directly from the nucleus. (In the second hypothesis, whether CHN is or is not the parent of the CN associated with the dust would need to be established.) The extended scalelengths found for CO by Eberhardt et. al. (1987) and for H2CO by Snyder et. al. (1989) also support ideas like hypothesis (2). A third hypothesis should be mentioned; contrary to the usual theory, the gas flow does not become isotropic (Combi 1987). For all of the reasons mentioned, it is essential to make a detailed comparison of the spatial distributions of CN and HCN. Furthermore, because of the variability of cometary emissions, it is necessary to make measurements simultaneously.

Palmer, Patrick↗
DOE OSTI2020

The structure of the RCAN1:CN complex explains the inhibition of and substrate recruitment by calcineurin

Regulator of calcineurin 1 (RCAN1) is an endogenous inhibitor of the Ser/Thr phosphatase calcineurin (CN). It has been shown that excessive inhibition of CN is a critical factor for Down syndrome and Alzheimer’s disease. Here, we determined RCAN1’s mode of action. Using a combination of structural, biophysical, and biochemical studies, we show that RCAN1 inhibits CN via multiple routes: first, by blocking essential substrate recruitment sites and, second, by blocking the CN active site using two distinct mechanisms. We also show that phosphorylation either inhibits RCAN1-CN assembly or converts RCAN1 into a weak inhibitor, which can be reversed by CN via dephosphorylation. This highlights the interplay between posttranslational modifications in regulating CN activity. Last, this work advances our understanding of how active site inhibition of CN can be achieved in a highly specific manner. Together, these data provide the necessary road map for targeting multiple neurological disorders.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

The CN radical in diffuse interstellar clouds

A survey of 15 lines of sight for the CN B2Sigma(+) X2Sigma(+) interstellar absorption lines shows that the CN column density in diffuse interstellar clouds follows the relation log N(CN) is proportional to m log N(H2), where m is approximately equal to 3. This result is reproduced by a reaction network in which CN is produced primarily from C2 by the neutral-neutral reaction C2 + N yields CN + C, and photodissociation is the main destruction pathway for the neutral molecules CH, C2, and CN. The CN radical is the first molecular species observed in diffuse clouds that requires a neutral-neutral reaction for its formation in the gas phase. The network also reproduces the observed ratio N(CN)/N(H2).

Federman, S. R.↗
NASA NTRS1994

Chemical transitions for interstellar C2 and CN in cloud envelopes

Observations were made of absorption from CH, C2, and CN toward moderately reddened stars in Sco, OB2, Ceo OB3, and Taurus/Auriga. For these directions, most of the reddening is associated with a single cloud complex, for example, the rho Ophiuchus molecular cloud, and as a result, the observations probe moderately dense material. When combined with avaliable data for nearby directions, the survey provides the basis for a comprehensive analysis of the chemistry for these species. The chemical transitions affecting C2 and CN in cloud envelopes were analyzed. The depth into a cloud at which a transition takes place was characterized by tau(sub uv), the grain optical depth at 1000 A. One transition at tau(sub uv) approx. = 2, which arises from, the conversion of C(+) into CO, affects the chemistries for both molecules because of the key role this ion plays. A second one involving production terms in the CN chemistry occurs at tau(sub uv) of approx. = 3; neutral reactions which C2 and CH is more important at larger values for tau(sub uv). The transition from photodissociation to chemical destruction takes place at tau(sub uv) approx. = 4.5 for C2 and CN. The observational data for stars in Sco OB2, Cep OB3, and Taurus/Auriga were studied with chemical rate equations containing the most important production and destruction mechanisms. Because the sample of stars in Sco OB2 includes sight lines with A(sub v) ranging from 1-4 mag, sight lines dominated by photochemistry could be analyzed separately from those controlled by gas-phase destruction. The analysis yielded values for two poorly known rate constants for reactions involved in the production of CN; the reactions are C2 + N yields CN + C and C(+) + NH yields all products. The other directions were analyzed with the inferred values. The predicted column densities for C2 and CN agree with the observed values to better than 50%, and in most instances 20%. When combining the estimates for density and temperature derived from chemical modeling and molecular excitation for a specific cloud, such as the rho Ophiuchus molecular cloud, the portion of the cloud envelope probed by C2 and CN absorption was found to be in pressure equilibrium.

Federman, S. R.↗
DOE OSTI2023

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Efficient energy-level alignment is crucial for achieving high performance in organic electronic devices. Because the electronic structure of an organic semiconductor is significantly influenced by its molecular orientation, comprehensively understanding the molecular orientation and electronic structure of the organic layer is essential. In this study, we investigated the interface between a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) hole injection layer and a zinc-phthalocyanine (ZnPc) p-type organic semiconductor. To determine the energy-level alignment and molecular orientation, we conducted in situ ultraviolet and X-ray photoelectron spectroscopies, as well as angle-resolved X-ray absorption spectroscopy. We found that the HAT-CN molecules were oriented relatively face-on (40°) in the thin (5 nm) layer, whereas they were oriented relatively edge-on (62°) in the thick (100 nm) layer. By contrast, ZnPc orientation was not significantly altered by the underlying HAT-CN orientation. The highest occupied molecular orbital (HOMO) level of ZnPc was closer to the Fermi level on the 100 nm thick HAT-CN layer than on the 5 nm thick HAT-CN layer because of the higher work function. Consequently, a considerably low energy gap between the lowest unoccupied molecular orbital level of HAT-CN and the HOMO level of ZnPc was formed in the 100 nm thick HAT-CN case. This may improve the hole injection ability of the anode system, which can be utilized in various electronic devices.

42 ENGINEERING↗
DOE OSTI2020

Crystal structure of dicaesium strontium hexacyanidoferrate(II), Cs 2 Sr[Fe(CN) 6 ], from laboratory X-ray powder data

Ferrocyanides with general formula A I x B II y [Fe(CN) 6 ], where A and B are cations, are thought to accept many substitutions on the A and B positions. In this communication, the synthesis and crystal structure of Cs 2 Sr[Fe(CN) 6 ] are reported. The latter was obtained from K 2 Ba[Fe(CN) 6 ] particles, put in contact with caesium and strontium ions. Hence, a simultaneous ion-exchange mechanism (Cs for K, Sr for Ba) occurs to yield Cs 2 Sr[Fe(CN) 6 ]. The synthesis protocol shows that K 2 BaFe(CN) 6 particles can be used for the simultaneous trapping of radioactive caesium and strontium nuclides in water streams. Cs 2 Sr[Fe(CN) 6 ] adopts the cryolite structure type and is isotypic with the known compound Cs 2 Na[Mn(CN) 6 ] [dicaesium sodium hexacyanidomanganate(III)]. The octahedrally coordinated Sr and Fe sites both are located on inversion centres, and the eightfold-coordinated Cs site on a general position.

Massoni, Nicolas↗