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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Spatio-temporal focal spot characterization and modeling of the NIF ARC kilojoule picosecond laser

The advanced radiographic capability (ARC) laser system, part of theNational Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is a short-pulse laser capability integrated into the NIF. The ARC is designed to provide adjustable pulse lengths of ~1–38 ps in four independent beamlets, each with energies up to 1 kJ (depending on pulse duration). A detailed model of the ARC lasers has been developed that predicts the time- and space-resolved focal spots on target for each shot. Measurements made to characterize static and dynamic wavefront characteristics of the ARC are important inputs to the code. Modeling has been validated with measurements of the time-integrated focal spot at the target chamber center (TCC) at low power, and the space-integrated pulse duration at high power, using currently available diagnostics. In this work, these simulations indicate that each of the four ARC beamlets achieves a peak intensity on target of up to a few 10 18 W=cm 2 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

An Active and Robust Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Reversible protonic ceramic electrochemical cells (RPCECs) are a promising option for efficient and low-cost generation of electricity and hydrogen. Commercialization of R-PCECs, however, hinges on the development of highly active and robust air electrodes. Here, we report an air electrode consisting of PrBa 0.8 Ca 0.2 Co 2 O 5+δ and in situ exsolved BaCoO 3–δ nanoparticles (PBCC–BCO) that shows minimal polarization resistance (~0.24 Ω cm 2 at 600 °C) and high stability when exposed to humidified air with 3–50% H 2 O. An R-PCEC utilizing PBCC-BCO demonstrates remarkable performances at 600 °C: achieving a peak power density of 1.06 W cm –2 in the fuel cell mode and a current density of 1.51 A cm –2 at 1.3 V in an electrolysis mode. More importantly, the RPCECs demonstrate an exceptionally high durability over 1833 h of continuous operation in the electrolysis mode. Furthermore, this work offers an efficient approach to design of high-performance and durable electrodes for R-PCECs.

25 ENERGY STORAGE↗
DOE OSTI2026

Rational design of high-performance low-loading oxygen reduction catalysts for alkaline fuel cells

The lack of mechanistic understanding and catalyst design principles for alkaline electrolytes, especially for the sluggish oxygen reduction reaction, has impeded the advancement of alkaline fuel cells. Here, in this study, we propose a modified volcano plot and apply this rationale to strategically design Pt nanosheets with PdH x nanosheets substrates. This catalyst exhibited high stability with a specific activity of 1.71 mA cm −2 at 0.95 V versus the reversible hydrogen electrode, surpassing the benchmark of Pt/C by 49-fold. Spectroscopic, electrochemical and electron microscopic characterizations revealed that such performance enhancement originated from tensile-strained Pt{111} facets, improving oxidative stability and suppressing carbon corrosion. In fuel cell testing, the catalyst enabled a peak power density of 1.67 W cm −2 with a loading of 10 µg PGM Cathode cm −2 . Further optimization delivered a peak power density of 21.7 W mg −1 PGM Cathode+Anode with a total specific catalyst cost US$\$$1.27 kW −1 , surpassing the US Department of Energy’s Pt group metal loading and cost targets. This study provides valuable insights into catalyst design for the alkaline oxygen reduction reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reactive Species and Reaction Pathways for the Oxidative Cleavage of 4-Octene and Oleic Acid with H 2 O 2 over Tungsten Oxide Catalysts

The oxidative cleavage of carbon-carbon double bonds (C=C) in alkenes and fatty acids produces aldehydes and acids valued as chemical intermediates. Solid tungsten oxide catalysts are low cost, non-toxic, and selective for the oxidative cleavage of C=C bonds with hydrogen peroxide (H 2 O 2 ) and are, therefore, a promising option for continuous processes. Despite the relevance of these materials, the elementary steps involved and their sensitivity to the form of W sites present on surfaces have not been described. In this work, we combine in situ spectroscopy and rate measurements to identify significant steps in the reaction, the reactive species present on catalysts, and examine differences between the kinetics of this reaction on isolated W atoms grafted to alumina and on those exposed on crystalline WO 3 nanoparticles. Raman spectroscopy shows that W-peroxo complexes (W-(η 2 -O 2 ) formed from H 2 O 2 ) react in a kinetically relevant step to produce epoxides, which undergo hydrolysis at protic surface sites. Subsequently, the CH 3 CN solvent deprotonates diols to form alpha hydroxy ketones that react to form aldehydes and water following nucleophilic attack of H 2 O 2 . Turnover rates for oxidative cleavage, determined by in situ site titrations, on WO x -Al 2 O 3 are 75% greater than those on WO 3 at standard conditions. These differences reflect activation enthalpies (ΔH ‡ ) for oxidative cleavage of 4-octene that are much lower for the isolated WO x sites (36±3 and 60±6 kJ∙mol -1 for WO x -Al 2 O 3 and WO 3 , respectively) and correlate strongly with the difference between enthalpies of adsorption for epoxyoctane (ΔH ads,epox ), which resembles the transition state for epoxidation. The WO x -Al 2 O 3 catalysts mediate oxidative cleavage of oleic acid with H 2 O 2 following a mechanism comparable to that for 4-octene. The WO 3 materials, however, form only the epoxide and do not cleave the C-C bond or produce aldehydes and acids. These differences reflect the distinct site requirements for these reaction pathways and indicate that acid sites required for diol formation are strongly inhibited by oleic acids and epoxides on WO 3 whereas the Al 2 O 3 support provides sites competent for this reaction and increase the yield of the oxidative cleavage products.

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

Hadronic uncertainties versus new physics for the W boson mass and Muon g – 2 anomalies

There are now two single measurements of precision observables that have major anomalies in the Standard Model: the recent CDF measurement of the W mass shows a 7σ deviation and the Muon g – 2 experiment at FNAL confirmed a long-standing anomaly, implying a 4.2σ deviation. Doubts regarding new physics interpretations of these anomalies could stem from uncertainties in the common hadronic contributions. We demonstrate that these two anomalies pull the hadronic contributions in opposite directions by performing electroweak fits in which the hadronic contribution was allowed to float. The fits show that including the g – 2 measurement worsens the tension with the CDF measurement and conversely that adjustments that alleviate the CDF tension worsen the g – 2 tension beyond 5σ. This means that if we adopt the CDF W mass measurement, the case for new physics in either the W mass or muon g – 2 is inescapable regardless of the size of the SM hadronic contributions. Lastly, we demonstrate that a mixed scalar leptoquark extension of the Standard Model could explain both anomalies simultaneously.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Sustainable and Inexpensive Polydimethylsiloxane Sponges for Daytime Radiative Cooling

Radiative cooling is an emerging cooling technology that can passively release heat to the environment. To obtain a subambient cooling effect during the daytime, chemically engineered structural materials are widely explored to simultaneously reject sunlight and preserve strong thermal emission. However, many previously reported fabrication processes involve hazardous chemicals, which can hinder a material’s ability to be mass produced. In order to eliminate the hazardous chemicals used in the fabrication of previous works, this article reports a white polydimethylsiloxane (PDMS) sponge fabricated by a sustainable process using microsugar templates. By substituting the chemicals for sugar, the manufacturing procedure produces zero toxic waste and can also be endlessly recycled via methods widely used in the sugar industry. The obtained porous PDMS exhibits strong visible scattering and thermal emission, resulting in an efficient temperature reduction of 4.6 °C and cooling power of 43 W m –2 under direct solar irradiation. In addition, due to the air-filled voids within the PDMS sponge, its thermal conductivity remains low at 0.06 W (m K) –1 . This unique combination of radiative cooling and thermal insulation properties can efficiently suppress the heat exchange with the solar-heated rooftop or the environment, representing a promising future for new energy-efficient building envelope material.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Global Importance of Secondary Ice Production

Measured ice crystal number concentrations are often orders of magnitude higher than the number concentrations of ice nucleating particles, indicating the existence of secondary ice production (SIP) in clouds. Here, we present the first study to examine the global importance of SIP through the droplet shattering during freezing of rain, ice-ice collision fragmentation, and rime splintering, using a global climate model. Our results show that SIP happens quite uniformly in the two hemispheres and dominates the ice formation in the moderately cold clouds with temperatures warmer than –15°C. SIP decreases the global annual average liquid water path by –14.6 g m –2 (–22%), increases the ice water path by 8.7 g m –2 (23%), improving the model agreement with observations. SIP changes the global annual average shortwave, longwave, and net cloud forcing by 2.1, –1.0, and 1.1 W m –2 , respectively, highlighting the importance of SIP on cloud properties on the global scale.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Demonstration of plasma mirror capability for the OMEGA Extended Performance laser system

A plasma mirror platform was developed for the OMEGA-EP facility to redirect beams, thus enabling more flexible experimental configurations as well as a platform that can be used in the future to improve laser contrast. The plasma mirror reflected a short pulse focusing beam at 22.5° angle of incidence onto a 12.5 μm thick Cu foil, generating Bremsstrahlung and k α x rays, and accelerating ions and relativistic electrons. By measuring these secondary sources, the plasma mirror key performance metrics of integrated reflectivity and optical quality are inferred. It is shown that for a 5 ± 2 ps, 310 J laser pulse, the plasma mirror integrated reflectivity was 62 ± 13% at an operating fluence of 1670 J cm –2 , and that the resultant short pulse driven particle acceleration and x-ray generation indicate that the on target intensity was 3.1 × 10 18 W cm –2 , which is indicative of a good post-plasma mirror interaction beam optical quality. By deriving the plasma mirror performance metrics from the secondary source scalings, it was simultaneously demonstrated that the plasma mirror is ready for adoption in short pulse particle acceleration and high energy photon generation experiments using the OMEGA-EP system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Characterization of light-induced potentials in the strong-field dissociation of O 2 +

In this work, we investigate theoretically the imprints of light-induced potentials (LIPs) on the dissociation dynamics of O 2 + molecular ions, as observable in angle-resolved fragment kinetic-energy-release (KER) spectra. Following the vibrational and rotational dynamics of the initial pump-laser-excited cationic nuclear wave packet, while accounting for the dipole coupling between the O 2 + ( a 4 Π u ) and O 2 + ( f 4 Π g ) electronic states in 800-nm 40-fs probe-laser pulses with peak intensities between 10 13 and 10 14 W / cm 2 , we calculate angle-resolved KER spectra which reveal characteristic energy- and angle-dependent fringe structures. These fringes shift downward in energy as the molecular alignment angle θ relative to the probe-pulse polarization direction increases from 0 to π / 2 . The angle-dependent shifts in the KER fringes increase for larger probe-pulse peak intensities and follow the angle and light-wave-intensity dependence of the vibrational spectrum in the associated Floquet bond-hardening well, which is a manifestation of transient O 2 + nuclear-probability trapping in the LIP during dissociation. By examining the rovibrational dynamics of the dissociating molecular cation near the light-induced conical intersection (LICI) in the cationic LIP surface at θ = π / 2 , we identify related angle-dependent structures in the KER spectra, suggesting a means for assessing the significance of LICIs in molecular dissociation pathways.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Molybdenum Disulfide Nanoribbons with Enhanced Edge Nonlinear Response and Photoresponsivity

MoS 2 nanoribbons have attracted increased interest due to their properties, which can be tailored by tuning their dimensions. Herein, the growth of MoS 2 nanoribbons and triangular crystals formed by the reaction between films of MoOx (2 2 nanoribbons arising from distinct contributions from the single–layer edges and multilayer core. Nanoscale imaging reveals a blue-shifted exciton emission of the monolayer edge compared to the isolated MoS 2 monolayers due to built-in local strain and disorder. We further report on an ultrasensitive photodetector made of a single MoS 2 nanoribbon with a responsivity of 8.72 × 10 2 A W –1 at 532 nm, among the highest reported up-to-date for single-nanoribbon photodetectors. These findings can inspire the design of MoS 2 semiconductors with tunable geometries for efficient optoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Revisiting particle dry deposition and its role in radiative effect estimates

Wet and dry deposition remove aerosols from the atmosphere, and these processes control aerosol lifetime and thus impact climate and air quality. Dry deposition is a significant source of aerosol uncertainty in global chemical transport and climate models. Dry deposition parameterizations in most global models were developed when few particle deposition measurements were available. However, new measurement techniques have enabled more size-resolved particle flux observations. We combined literature measurements with data that we collected over a grassland in Oklahoma and a pine forest in Colorado to develop a dry deposition parameterization. We find that relative to observations, previous parameterizations overestimated deposition of the accumulation and Aitken mode particles, and underestimated in the coarse mode. These systematic differences in observed and modeled accumulation mode particle deposition velocities are as large as an order of magnitude over terrestrial ecosystems. As accumulation mode particles form most of the cloud condensation nuclei (CCN) that influence the indirect radiative effect, this model-measurement discrepancy in dry deposition alters modeled CCN and radiative forcing. We present a revised observationally driven parameterization for regional and global aerosol models. Using this revised dry deposition scheme in the Goddard Earth Observing System (GEOS)-Chem chemical transport model, we find that global surface accumulation-mode number concentrations increase by 62% and enhance the global combined anthropogenic and natural aerosol indirect effect by −0.63 W m −2 . Our observationally constrained approach should reduce the uncertainty of particle dry deposition in global chemical transport models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

CO 2 fertilization of crops offsets yield losses due to future surface ozone damage and climate change

Tropospheric ozone (O 3 ) is harmful to plant productivity and negatively impacts crop yields. O3 concentrations are projected to decrease globally in the optimistic Representative Concentration Pathway of 2.6 W m –2 (RCP2.6) but increase globally following the high-emission scenario under the RCP8.5, with substantial implications for global food security. The damaging effect of O 3 on future crop yield is affected by CO 2 fertilization and climate change, and their interactions for RCP scenarios have yet to be quantified. In this study, we used the Joint UK Land Environment Simulator modified to include crops (JULES-crop) to quantify the impacts, and relative importance of present-day and future O3, CO 2 concentration and meteorology on crop production at the regional scale until 2100 following RCP2.6 and RCP8.5 scenarios. We focus on eight major crop-producing regions that cover the production of wheat, soybean, maize, and rice. Our results show that CO 2 alone has the largest effect on regional yields, followed by climate and O 3 . However, the CO 2 fertilization effect is offset by the negative impact of tropospheric O 3 in regions with high O 3 concentrations, such as South Asia and China. Simulated crop yields in 2050 were compared with Food and Agriculture Organisation (FAO) statistics to investigate the differences between a socioeconomic and a biophysical process-based approach. Results showed that FAO estimates are closer to our JULES-crop RCP8.5 scenario. This study demonstrates that air pollution could be the biggest threat to future food production and highlights an urgent policy need to mitigate the threat of climate change and O 3 pollution on food security.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

First results on nucleon resonance electroexcitation amplitudes from ep → e'π + π – p' cross sections at W = 1.4–1.7 GeV and Q 2 = 2.0–5.0 GeV 2

The electroexcitation amplitudes or $\gamma_vpN^*$ electrocouplings of the $N(1440)1/2^+$, $N(1520)3/2^-$, and $\Delta(1600)3/2^+$ resonances were obtained for the first time from the $ep \to e'\pi^+\pi^-p'$ differential cross sections measured with the CLAS detector at Jefferson Lab within the range of invariant mass $W$ of the final state hadrons from 1.4–1.7~GeV for photon virtualities $Q^2$ from 2.0--5.0~GeV$^2$. A good description of the nine independent one-fold differential $\gamma_v p\to \pi^+\pi^-p'$ cross sections achieved within the data-driven Jefferson Lab-Moscow State University (JM) meson-baryon reaction model in each bin of ($W$,$Q^2$) allows for separation of the resonant and non-resonant contributions. The electrocouplings were determined in the fits of the $\pi^+\pi^-p$ cross sections within three overlapping $W$ intervals with a substantial contribution from each of the three resonances listed above. Consistent results on the electrocouplings extracted from the data in these $W$ intervals provide evidence for their reliable extraction. These studies extend information on the electrocouplings of the $N(1440)1/2^+$ and $N(1520)3/2^-$ available from this channel over a broader range of $Q^2$. The electrocouplings of the $\Delta(1600)3/2^+$, which decays preferentially into $\pi\pi N$ final states, have been determined for the first time. Here, the reliable extraction of the electrocouplings for these states is also supported by the description of the $\pi^+\pi^-p$ differential cross sections with $Q^2$-independent masses and total/partial hadronic decay widths into the $\pi\Delta$ and $\rho p$ final states.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Materials Data on Na5(WO3)14 by Materials Project

Na5(WO3)14 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with ten NaO12 cuboctahedra and faces with eight WO6 octahedra. There are two shorter (2.72 Å) and ten longer (2.75 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with six equivalent NaO12 cuboctahedra and faces with eight WO6 octahedra. There are a spread of Na–O bond distances ranging from 2.72–2.75 Å. In the third Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with seven NaO12 cuboctahedra and faces with eight WO6 octahedra. There are a spread of Na–O bond distances ranging from 2.72–2.76 Å. There are four inequivalent W+5.64+ sites. In the first W+5.64+ site, W+5.64+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six WO6 octahedra and faces with three NaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 1–3°. There are a spread of W–O bond distances ranging from 1.93–1.96 Å. In the second W+5.64+ site, W+5.64+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six WO6 octahedra and faces with four NaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. All W–O bond lengths are 1.95 Å. In the third W+5.64+ site, W+5.64+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six WO6 octahedra and faces with three equivalent NaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of W–O bond distances ranging from 1.93–1.96 Å. In the fourth W+5.64+ site, W+5.64+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six WO6 octahedra and faces with two NaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. All W–O bond lengths are 1.95 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+ and two equivalent W+5.64+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+ and two equivalent W+5.64+ atoms. In the third O2- site, O2- is bonded in a distorted square co-planar geometry to two equivalent Na1+ and two equivalent W+5.64+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Na1+ and two W+5.64+ atoms. In the fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+ and two W+5.64+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+ and two equivalent W+5.64+ atoms. In the seventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+ and two equivalent W+5.64+ atoms. In the eighth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+ and two equivalent W+5.64+ atoms. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+ and two equivalent W+5.64+ atoms. In the tenth O2- site, O2- is bonded in a distorted square co-planar geometry to two equivalent Na1+ and two equivalent W+5.64+ atoms. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+ and two W+5.64+ atoms. In the twelfth O2- site, O2- is bonded in a distorted square co-planar geometry to two equivalent Na1+ and two equivalent W+5.64+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Quantifying contributions of ozone changes to global and arctic warming during the second half of the twentieth century

Ozone is the third most important greenhouse gas in driving global warming, mainly due to increased tropospheric ozone. About 50% of the growth of global tropospheric ozone since preindustrial time occurred during 1955–2005, with continued growth since then. Furthermore, this study quantifies the relative contributions of ozone changes during 1955–2005 to total observed global and Arctic climate changes by comparing CESM1 historical simulations with all anthropogenic and natural radiative forcings including realistic ozone changes, and with the same forcings except with constant ozone or well-mixed greenhouse gases (WMGHG). Results indicate that ozone changes during 1955–2005 have strongly enhanced the downwelling longwave flux and increased net shortwave flux at the surface, and thus significantly contributed about 0.15 °C of global mean surface warming, roughly 21%, 26% and 16% of the observed, all-forcing and WMGHG-driven trends, respectively. In the Arctic in the same period, corresponding ozone-driven warming was about 0.63 °C, roughly 48%, 40% and 25% of the same three trends. During 1979–2005, these ozone changes have markedly added about 0.25 × 10 6 km 2 to the decrease in the Arctic sea ice extent (SIE), or roughly 25%, 48%, and 40% of the same three trends. Considering that the ozone-driven radiative forcing of about 0.22 (0.06) W·m –2 in 1955–2005 (1979–2005) was about 12% (6%) of the corresponding WMGHG forcing, ozone changes had contributed disproportionately to global and Arctic warming and Arctic sea ice decline during the second half of the twentieth century. Tropospheric ozone has shown relatively steady growth since 2006 and might have significantly contributed recent observed warming over the global and the Arctic.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on ReWO6 by Materials Project

WReO6 is High-temperature superconductor-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. W6+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six equivalent ReO6 octahedra. The corner-sharing octahedra tilt angles range from 1–2°. All W–O bond lengths are 1.94 Å. Re6+ is bonded to six O2- atoms to form ReO6 octahedra that share corners with six equivalent WO6 octahedra. The corner-sharing octahedra tilt angles range from 1–2°. All Re–O bond lengths are 1.89 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one W6+ and one Re6+ atom. In the second O2- site, O2- is bonded in a linear geometry to one W6+ and one Re6+ atom. In the third O2- site, O2- is bonded in a linear geometry to one W6+ and one Re6+ atom. In the fourth O2- site, O2- is bonded in a linear geometry to one W6+ and one Re6+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to one W6+ and one Re6+ atom. In the sixth O2- site, O2- is bonded in a linear geometry to one W6+ and one Re6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3(WO3)4 by Materials Project

Na3(WO3)4 crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Na1+ is bonded to twelve equivalent O2- atoms to form NaO12 cuboctahedra that share corners with eight equivalent NaO12 cuboctahedra, faces with four equivalent NaO12 cuboctahedra, and faces with eight equivalent WO6 octahedra. There are four shorter (2.75 Å) and eight longer (2.78 Å) Na–O bond lengths. W+5.25+ is bonded to six equivalent O2- atoms to form WO6 octahedra that share corners with six equivalent WO6 octahedra and faces with six equivalent NaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. All W–O bond lengths are 1.97 Å. O2- is bonded to three equivalent Na1+ and two equivalent W+5.25+ atoms to form a mixture of distorted corner, edge, and face-sharing ONa3W2 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni2W11C4 by Materials Project

W11Ni2C4 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are ten inequivalent W sites. In the first W site, W is bonded in a 1-coordinate geometry to eleven W, one Ni, and one C atom. There are a spread of W–W bond distances ranging from 2.66–3.00 Å. The W–Ni bond length is 2.61 Å. The W–C bond length is 2.69 Å. In the second W site, W is bonded to twelve W atoms to form WW12 cuboctahedra that share corners with four equivalent CNi2W4 octahedra, faces with two equivalent WW12 cuboctahedra, and faces with four equivalent CNiW5 octahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of W–W bond distances ranging from 2.61–2.99 Å. In the third W site, W is bonded in a 2-coordinate geometry to two equivalent W and two Ni atoms. Both W–W bond lengths are 2.61 Å. There are one shorter (2.59 Å) and one longer (2.64 Å) W–Ni bond lengths. In the fourth W site, W is bonded in a 2-coordinate geometry to two equivalent W and two equivalent Ni atoms. Both W–W bond lengths are 2.57 Å. Both W–Ni bond lengths are 2.61 Å. In the fifth W site, W is bonded to twelve W atoms to form distorted WW12 cuboctahedra that share edges with six CNi2W4 octahedra and faces with three WW12 cuboctahedra. There are a spread of W–W bond distances ranging from 2.90–3.01 Å. In the sixth W site, W is bonded in a distorted bent 150 degrees geometry to two W and two C atoms. There are one shorter (2.12 Å) and one longer (2.14 Å) W–C bond lengths. In the seventh W site, W is bonded in a 2-coordinate geometry to two W and two equivalent C atoms. Both W–C bond lengths are 2.12 Å. In the eighth W site, W is bonded in a 2-coordinate geometry to three W and two C atoms. There are one shorter (2.13 Å) and one longer (2.15 Å) W–C bond lengths. In the ninth W site, W is bonded in a distorted bent 150 degrees geometry to three W and two equivalent C atoms. Both W–C bond lengths are 2.14 Å. In the tenth W site, W is bonded in a 3-coordinate geometry to two W and three C atoms. There are one shorter (2.02 Å) and two longer (2.18 Å) W–C bond lengths. There are three inequivalent Ni sites. In the first Ni site, Ni is bonded in a distorted T-shaped geometry to two equivalent W and three C atoms. There is one shorter (1.86 Å) and two longer (2.09 Å) Ni–C bond length. In the second Ni site, Ni is bonded in a 3-coordinate geometry to two W and three C atoms. There is one shorter (1.94 Å) and two longer (2.04 Å) Ni–C bond length. In the third Ni site, Ni is bonded in a 3-coordinate geometry to two equivalent W and three C atoms. There is one shorter (1.90 Å) and two longer (2.05 Å) Ni–C bond length. There are four inequivalent C sites. In the first C site, C is bonded in a 1-coordinate geometry to four W and one Ni atom. In the second C site, C is bonded in a trigonal planar geometry to three Ni atoms. In the third C site, C is bonded to five W and one Ni atom to form CNiW5 octahedra that share corners with six CNiW5 octahedra, edges with two equivalent WW12 cuboctahedra, and a faceface with one WW12 cuboctahedra. The corner-sharing octahedra tilt angles range from 22–45°. In the fourth C site, C is bonded to four W and two Ni atoms to form CNi2W4 octahedra that share corners with two equivalent WW12 cuboctahedra, corners with six CNiW5 octahedra, and edges with two equivalent WW12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–41°.

36 MATERIALS SCIENCE↗