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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

High-resolution crystal structure reveals a HEPN domain at the C-terminal region of S. cerevisiae RNA endonuclease Swt1

Highlights: • Crystal structure of the C-terminal (CT) domain of Swt1 was determined at 2.3 Å. • Structure of the CT domain was identified as HEPN domain superfamily member. • Low-resolution envelope of Swt1 full-length in solution was analyzed by SAXS. • The middle and CT domains gave good fit to SAXS structural model. - Abstract: Swt1 is an RNA endonuclease that plays an important role in quality control of nuclear messenger ribonucleoprotein particles (mRNPs) in eukaryotes; however, its structural details remain to be elucidated. Here, we report the crystal structure of the C-terminal (CT) domain of Swt1 from Saccharomyces cerevisiae, which shares common characteristics of higher eukaryotes and prokaryotes nucleotide binding (HEPN) domain superfamily. To study in detail the full-length protein structure, we analyzed the low-resolution architecture of Swt1 in solution using small angle X-ray scattering (SAXS) method. Both the CT domain and middle domain exhibited a good fit upon superimposing onto the molecular envelope of Swt1. Our study provides the necessary structural information for detailed analysis of the functional role of Swt1, and its importance in the process of nuclear mRNP surveillance.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Synthesis and structural characterization of Al{sub 7}C{sub 3}N{sub 3}-homeotypic aluminum silicon oxycarbonitride, (Al{sub 7-x}Si{sub x})(O{sub y}C{sub z}N{sub 6-y-z}) (x{approx}1.2, y{approx}1.0 and z{approx}3.5)

A new aluminum silicon oxycarbonitride, (Al{sub 5.8}Si{sub 1.2})(O{sub 1.0}C{sub 3.5}N{sub 1.5}), has been synthesized and characterized by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). The title compound is hexagonal with space group P6{sub 3}/mmc and unit-cell dimensions a=0.322508(4) nm, c=3.17193(4) nm and V=0.285717(6) nm{sup 3}. The atom ratios of Al:Si and those of O:C:N were, respectively, determined by EDX and EELS. The initial structural model was successfully derived from the XRPD data by the direct methods and further refined by the Rietveld method. The crystal is most probably composed of four types of domains with nearly the same fraction, each of which is isotypic to Al{sub 7}C{sub 3}N{sub 3} with space group P6{sub 3}mc. The existence of another new oxycarbonitride (Al{sub 6.6}Si{sub 1.4})(O{sub 0.7}C{sub 4.3}N{sub 2.0}), which must be homeotypic to Al{sub 8}C{sub 3}N{sub 4}, has been also demonstrated by XRPD and TEM. - Graphical abstract: A new oxycarbonitride discovered in the Al-Si-O-C-N system, (Al{sub 7-x}Si{sub x})(O{sub y}C{sub z}N{sub 6-y-z}) (x{approx}1.2, y{approx}1.0 and z{approx}3.5). The crystal is composed of four types of domains (I, II, III and IV), and hence the structure is represented by a split-atom model. Individual crystal structures can be regarded as layered structures, which consist of A-type [(Al, Si){sub 4}(O, C, N){sub 4}] unit layers and B-type [(Al, Si)(O, C, N){sub 2}] single layers. Highlights: > (Al{sub 5.8}Si{sub 1.2})(O{sub 1.0}C{sub 3.5}N{sub 1.5}) as a new aluminum silicon oxycarbonitride. > Crystal structure is determined and represented by a split-atom model. > Existence of another new oxycarbonitride (Al{sub 6.6}Si{sub 1.4})(O{sub 0.7}C{sub 4.3}N{sub 2.0}) is demonstrated. > Both new materials are formed by oxidation and nitridation of (Al, Si){sub 6}(O, C){sub 5}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

ROMULIS 1.01.00

The Reduced Order Modeling Unlimited Localized Interface Simulator (ROMULIS) is a set of toolbox scripts in MATLAB designed to perform nonlinear transient integration on a system of reduced order structural models that interact with each other at localized interfaces. ROMULIS is meant to provide a user-friendly interface for applying the latest developments in numerical techniques and modeling in structural dynamics analysis while also giving the freedom to implement new technologies from forthcoming research. This report documents how to use and interpret the toolbox scripts. The theory behind the code is given, followed by a manual for interacting with the scripts to perform simulations. Lastly, a high-level introduction that explains how the scripts interact with each other is given for aspiring developers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Implementation of a self-consistent slab model of bilayer structure in the SasView suite

Slab models are simple and useful structural descriptions which have long been used to describe lyotropic lamellar phases, such as lipid bilayers. Typically, slab models assume a midline symmetry and break a bilayer structure into three pieces, a central solvent-free core and two symmetric outer layers composed of the soluble portion of the amphiphile and associated solvent. This breakdown matches reasonably well to the distribution of neutron scattering length density and therefore is a convenient and common approach for the treatment of small-angle scattering data. Here, an implementation of this model within the SasView software suite is reported. The implementation is intended to provide physical consistency through the area per amphiphile molecule and number of solvent molecules included within the solvent-exposed outer layer. The proper use of this model requires knowledge of (or good estimates for) the amphiphile and solvent molecule volume and atomic composition, ultimately providing a self-consistent data treatment with only two free parameters: the lateral area per amphiphile molecule and the number of solvent molecules included in the outer region per amphiphile molecule. Here, the use of this code is demonstrated in the fitting of standard lipid bilayer data sets, obtaining structural parameters consistent with prior literature and illustrating the typical and ideal cases of fitting for neutron scattering data obtained using single or multiple contrast conditions. While demonstrated here for lipid bilayers, this model is intended for general application to block copolymers, surfactants, and other lyotropic lamellar phase structures for which a slab model is able to reasonably estimate the neutron scattering length density/electron-density profile of inner and outer layers of the lamellae.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Morphology, structure, and chemistry of nanoclusters in a mechanically alloyed nanostructured ferritic steel

Nanostructured ferritic steels have excellent high temperature creep properties and radiation tolerance due to the presence of a high density of Ti-Y-O-enriched nanoclusters. The morphology of the nanoclusters is found to be consistent with a truncated rhombic dodecahedron defined by the {l_brace}100{r_brace} and {l_brace}110{r_brace} planes in the Fe matrix. The derived symmetry and the compositional information indicate that the nanoclusters are inconsistent with the cubic Y2Ti2O7 or the polymorphs of Y2TiO5 phase. Possible structural models are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

A new theory for X-ray diffraction

By considering the scattering distributed throughout space, there is an intensity enhancement at the Bragg angle even when the Bragg condition is not satisfied. This leads to an alternative explanation for the diffraction from powders and small crystals. This article proposes a new theory of X-ray scattering that has particular relevance to powder diffraction. The underlying concept of this theory is that the scattering from a crystal or crystallite is distributed throughout space: this leads to the effect that enhanced scatter can be observed at the ‘Bragg position’ even if the ‘Bragg condition’ is not satisfied. The scatter from a single crystal or crystallite, in any fixed orientation, has the fascinating property of contributing simultaneously to many ‘Bragg positions’. It also explains why diffraction peaks are obtained from samples with very few crystallites, which cannot be explained with the conventional theory. The intensity ratios for an Si powder sample are predicted with greater accuracy and the temperature factors are more realistic. Another consequence is that this new theory predicts a reliability in the intensity measurements which agrees much more closely with experimental observations compared to conventional theory that is based on ‘Bragg-type’ scatter. The role of dynamical effects (extinction etc.) is discussed and how they are suppressed with diffuse scattering. An alternative explanation for the Lorentz factor is presented that is more general and based on the capture volume in diffraction space. This theory, when applied to the scattering from powders, will evaluate the full scattering profile, including peak widths and the ‘background’. The theory should provide an increased understanding of the reliability of powder diffraction measurements, and may also have wider implications for the analysis of powder diffraction data, by increasing the accuracy of intensities predicted from structural models.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

A neutron diffraction study and mode analysis of compounds of the system La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x} (x=1, 0.8, 0.5, 0.2) and an investigation of their magnetic properties

We report here a detailed study of the system La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x}, by neutron powder diffraction- and magnetic-measurements. All the compounds are robust antiferromagnetics with ordering temperatures well above room temperature. Magnetic moments are shown to align parallel to the c-axis. FC-ZFC measurements indicate a small canting of the magnetic moments, resulting in a ferromagnetic component with a maximum for La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}. We show that the system exhibits a composition-driven transition from a phase, for low fluorination levels (x≤0.5), with Pnma symmetry and the usual system of octahedral tiltings, to a phase with space group Imma for higher fluorine contents, where a correlated distortion of the oxygen octahedra plays a significant role. The consistency of the structural models, with respect to the expected continuity of the amplitudes of the different distortion modes and the invariance of their internal form, was monitored through the symmetry mode decomposition of the structures. - Graphical abstract: The crystal and magnetic structure of La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}. Display Omitted - Highlights: • The compounds La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x} (x=1, 0.8, 0.5, 0.2) were studied by neutron diffraction. • A mode analysis shows lower symmetry for Sr rich compounds than previously reported. • SrFeO{sub 2}F crystallizes in the orthorhombic space group Imma. • Magnetic moments resulting from canting depend on metric distortion. • The magnetic structure was determined for La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Novel Zoned Waste-forms for High-Priority Radionuclide Waste Streams

This report describes the potential of a novel class of materials—α-ZrW 2 O 8 , Zr 2 WP 2 O 12 , and related compounds that contract upon amorphization as possible radionuclide waste-forms. The proposed ceramic waste-forms would consist of zoned grains, or sintered ceramics with center- loaded radionuclides and barren shells. Radiation-induced amorphization would result in core shrinkage but would not fracture the shells or overgrowths, maintaining isolation of the radionuclide. In this report, we have described synthesis techniques to produce phase-pure forms of the materials, and how to fully densify those materials. Structural models for the materials were developed and validated using DFPT approaches, and radionuclide substitution was evaluated; U(IV), Pu(IV), Tc(IV) and Tc(VII) all readily substitute into the material structures. MD modeling indicated that strain associated with radiation-induced amorphization would not affect the integrity of surrounding crystalline materials, and these results were validated via ion beam experimental studies. Finally, we have evaluated the leach rates of the barren materials, as determined by batch and flow-through reactor experiments. ZrW 2 O 8 leaches rapidly, releasing tungstate while Zr is retained as a solid oxide or hydroxide. Tungsten release rates remain elevated over time and are highly sensitive to contact times, suggesting that this material will not be an effective waste-form. Conversely, tungsten releases rates from Zr 2 WP 2 O 12 rapidly drop, show little dependence on short-term changes in fluid contact time, and in over time, become tied to P release rates. The results presented here suggest that this material may be a viable waste-form for some hard-to-handle radionuclides such as Pu and Tc.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Unraveling the Molecular Origin of Prey-Wrapping Spider Silk's Unique Mechanical Properties and Assembly Process Using NMR

Prey wrapping spider silk's unique mechanical properties are investigated confirming the silk's high degree of extensibility and superior toughness compared to other types of spider silk. For the first time, the pre-spinning dope phase is studied in isotope-enriched intact aciniform (AC) silk glands using solution NMR that reveals a combination of α-helical domains linked by disordered random coil chains consistent with previously proposed “beads-on-a-string” models. The model is further refined through the AlphaFold2 protein structure prediction tool. Finally, extensive magic angle spinning (MAS) solid-state (SS) NMR data for isotopically-enriched fibers is used to refine the structural model for AC silk from two species, A. aurantia and A. argentata. The SSNMR data shows that the AC silk fibers are highly α-helical, coiled-coil in structure but, also exhibit significant β-sheet components that can be traced back to the Gly-rich disordered linker regions in the pre-spinning dope phase that are converted to β-sheet structures during fiber formation. This combination of mechanical and structural characterization enhances the understanding of AC silk's liquid-to-solid transition and structure-mechanics relationship. In conclusion, these prey wrap silk results and models will provide the basis for the design of biomimetic materials inspired by the AC spider silk system.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Disordered surface structure of an ultra-thin tin oxide film on Rh(100)

The composition and structure of an ultra-thin tin oxide film on Rh(100), prepared by the deposition of a submonolayer of tin followed by annealing in an O{sub 2} atmosphere, were examined by a combination of low-energy electron diffraction (LEED), Auger electron spectroscopy, X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM), and ab initio calculations based on density functional theory (DFT). Although the LEED pattern exhibited c(2 x 8) spots clearly, a uniform periodicity of the c(2 x 8) unit cell was not observed in the STM images. The bright dots that were observed periodically in the STM image were similar to those of the ultra-thin Sn{sub 2}O{sub 3} film on Rh(111) and formed a zigzag arrangement with the numerous point and line defects. The XPS study revealed that the Sn 3d{sub 5/2} peak of the tin oxide film on Rh(100) showed a metallic state as well as an oxide state that was between the SnO{sub 2} and SnO states. The structural models, which were based on the Sn{sub 2}O{sub 3} structure on Rh(111), were determined using DFT total energy calculations. The simulated STM images of the two slightly different honeycomb-chain models well reproduced the zigzag arrangement in the STM image. The STM image and XPS spectrum were interpreted using a combination of the two models.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mirror nucleon removal reactions in p-shell nuclei

Nucleon removal reactions have been shown to be an effective tool for studying the single particle structure of nuclei. This work continues efforts to experimentally probe and benchmark the reaction and structure models used to calculate the removal reaction cross sections when using microscopic nuclear structure inputs. Here, three different single nucleon removal reactions were performed, from p -shell nuclei with masses A = 7, 9, and 10. The residual nuclei from the reactions were detected in coincidence with γ rays to determine partial cross sections to individual final states. The eikonal direct-reaction model is combined with overlap functions and residual nucleus densities from microscopic, variational Monte Carlo calculations to provide consistent nuclear structure input to the partial cross section calculations. Comparisons of measured and calculated cross sections, including for mirror reactions, are presented. The analysis of the partial cross sections leading to the ground states shows a similar behavior to the one observed from analyses of inclusive cross sections using shell model nuclear structure input: the theoretical description of the removal process is in better agreement with the data when removing weakly bound nucleons, than when removing well-bound ones. The two mirror reaction pairs presented here show consistent results between the respective members of the pairs. The results obtained for the population of the excited states, however, show a systematically different trend that appears connected to the structure part of the calculation. Additional cases are needed to better understand the respective roles of structure and dynamical effects in the deviations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Novel Synthesis and Structural Analysis of Ferrihydrite

Naturally occurring ferrihydrite is both impure and difficult to isolate, so the numerous applications and interesting properties of ferrihydrite have spurred the development of various synthetic techniques. Nearly all techniques are based on the hydrolysis of an iron salt and require careful control of temperature, pH, and concentration. In this Article, we report a new synthetic method which does not require such control and is perhaps the fastest and simplest route to synthesizing ferrhydrite. XRD, TEM, BET, and chemical purity characterizations show that the chemically pure, 2-line ferrihydrite product consists of crystallites 2-6 nm in diameter which aggregate to form mesoporous, high surface area agglomerates that are attractive candidates for the many adsorption applications of ferrihydrite. X-ray PDF data were also collected for the ferrihydrite product and refined against the hexagonal structural model recently proposed by Michel et al. These analyses suggest that ferrihydrite has a consistent, repeatable structure independent of variation in the synthetic method, water content of the sample, or particle size of the crystallites, and this structure can be adequately described by the proposed hexagonal model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Pore structure refinement of cement paste incorporating nanosilica: Study with dual beam scanning electron microscopy/focused ion beam (SEM/FIB)

Highlights: • The modifying effects of nanosilica on pore structure of cement-based composites are investigated. • Dual beam SEM/FIB is implemented to create the 3D pore structure model and calculate porosity and pore size distribution. • The porosity and pore diameter are found to decrease with the inclusion of nanosilica. - Abstract: Pozzolanic materials, micro- and nano-, have been found to improve the durability properties of cement-based materials by refining their pore structure. As a relatively newer material, the modifying effects of nanosilica on pore structure are still inconclusive in the literature. In this study, this was characterized by implementing dual beam SEM/FIB, which can generate 3D models of porous materials for quantitative analysis. The sample is milled by focused ion beam layer-by-layer, and each surface layer is 2D imaged via scanning electron microscopy. Three types of pores – large capillary pore, medium capillary pore and gel pore – can be observed. A 3D pore structure model is then reconstructed from 1000 of these 2D images, from which porosity and pore size distribution can be calculated. Cement pastes incorporating nanosilica and silica fume were compared. The porosity and pore diameter were found to decrease with the inclusion of nanosilica. Furthermore, reduction in capillary pores and subsequent increase in gel pores were also observed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Chromium substitution in mullite type bismuth aluminate: Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with 0≤x≤2.0

Nominal compositions Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with 0.0≤x≤2.0 (Δx=0.2) were prepared using appropriate amounts of nitrates dissolved in glycerine and heated at 800 °C for 24 h as we previously used for the preparation of solid solution series Bi{sub 2}M{sub x}/M′{sub 4−x}O{sub 9} (M/M′=Fe/Al, Ga/Al and Fe/Ga). The samples were characterized using XRD, FTIR and optical microscopic techniques. Analyses of XRD data show mullite type single phase can be prepared up to x=1.2. The lattice parameters (a, b and c) increases with increasing Cr content. Further increase in x (i.e., x≥1.4) show the presence of some additional phases indicating a limiting value for Cr doping is in the range of 1.2≤x<1.4. The effect of Cr incorporation could also be observed in the infrared absorption spectra via systematic hard mode shifts of certain lattice modes, e.g. the Bi–O related vibration changes from 96 cm{sup −1} to 93 cm{sup −1} with increasing x up to 1.2 and certain intensity changes together with shift in peak positions. Interestingly, the absence of any splitting and shift of the high energy IR absorption peak at 821 cm{sup −1} as assigned to the characteristic tetrahedral type dimer, Al{sub 2}O{sub 7}, indicate that the Cr thus partially substitutes only the octahedrally coordinated Al. This is confirmed by Rietveld structure refinements, too. - Graphical abstract: Structural model of Cr doped bismuth aluminate, Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9}. - Highlights: • Chromium doped bismuth aluminate, Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with mullite type structure are synthesized. • The samples are characterized by XRD and FTIR techniques. • Cr can replace only certain amount of octahedrally coordinated Al in Bi{sub 2}Al{sub 4}O{sub 9} under present experimental conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

A Synchrotron-Based Hydroxyl Radical Footprinting Analysis of Amyloid Fibrils and Prefibrillar Intermediates with Residue-Specific Resolution

The structural models of the fibrils formed by the 40-residue amyloid-β (Aβ40) peptide in Alzheimer’s disease typically consist of linear polypeptide segments, oriented approximately perpendicular to the long axis of the fibril, and joined together as parallel in-register β-sheets to form filaments. However, various models differ in the number of filaments that run the length of a fibril, and in the topological arrangement of these filaments. In addition to questions about the structure of Aβ40 monomers in fibrils, there are important unanswered questions about their structure in prefibrillar intermediates, which are of interest because they may represent the most neurotoxic form of Aβ40. To assess different models of fibril structure and to gain insight into the structure of prefibrillar intermediates, the relative solvent accessibility of amino acid residue side chains in fibrillar and prefibrillar Aβ40 preparations was characterized in solution by hydroxyl radical footprinting and structural mass spectrometry. A key to the application of this technology was the development of hydroxyl radical reactivity measures for individual side chains of Aβ40. When we combined mass-per-length measurements performed by dark-field electron microscopy, we determined that the results of our study were consistent with the core filament structure represented by two- and three-filament solid state nuclear magnetic resonance-based models of the Aβ40 fibril (such as 2LMN, 2LMO, 2LMP, and 2LMQ), with minor refinements, but they are inconsistent with the more recently proposed 2M4J model. Our results also demonstrate that individual Aβ40 fibrils exhibit structural heterogeneity or polymorphism, where regions of two-filament structure alternate with regions of three-filament structure. The footprinting approach utilized in this study will be valuable for characterizing various fibrillar and nonfibrillar forms of the Aβ peptide.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Structural Analysis Results of Thermal, Operating and Seismic Analysis for Hanford Single-Shell Tank Integrity - 12261

Since Hanford's 149 Single-Shell Tanks (SSTs) are well beyond their design life, the U.S. Department of Energy has commissioned a state of the art engineering analysis to assess the structural integrity of the tanks to ensure that they are fit for service during the cleanup and closure phase. The structural integrity analysis has several challenging factors. There are four different tank sizes in various configurations that require analysis. Within each tank type there are different waste level and temperature histories, soil overburden depths, tank floor arrangements, riser sizes and locations, and other on-tank structures that need to be addressed. Furthermore, soil properties vary throughout the tank farms. This paper describes the structural integrity analysis that was performed for the SSTs using finite element models that incorporate the detailed design features of each tank type. The analysis was performed with two different models: an ANSYS static model for the Thermal and Operating Loads Analysis, and an ANSYS dynamic model for the seismic analysis. The TOLA analyses simulate the waste level and thermal history and it included a matrix of analysis cases that bounded the material property uncertainties. The TOLA also predicts the occurrence of concrete thermal degradations and cracking, reinforcement yielding, and soil plasticity. The seismic analysis matrix included uncertainty in waste properties, waste height and the soil modulus. In seismic analysis the tank concrete was modeled as a linear elastic material that was adjusted for the present day degraded conditions. Also, the soil was treated as a linear elastic material while special modeling techniques were used to avoid soil arching and achieve proper soil pressure on the tank walls. Seismic time histories in both the horizontal and vertical directions were applied to the seismic model. Structural demands from both Thermal and Operating Loads Analysis and seismic models were extracted in the form of section forces and moments for sections throughout the tank under the appropriate load combinations. These demands were evaluated against the American Concrete Institute (ACI) code requirements for nuclear safety-related concrete structures as defined in ACI-349-06. Structural integrity analysis of Hanford's Type II and Type III Single-Shell Tanks (SSTs) was performed using finite element models (ANSYS software) that incorporate the detailed design features of each tank type. The analysis was performed with two different models: a static model for the Thermal and Operating Loads Analysis, and a dynamic model for the seismic analysis. Structural demands from both Thermal and Operating Loads Analysis and seismic models were evaluated against the American Concrete Institute (ACI) code requirements for nuclear safety-related concrete structures as defined in ACI-349-06. The ratio of demand to capacity (D/C) was reported as a measure of structural integrity for the applicable ACI-349-06 load combinations. Although the Type II and Type III analysis matrix showed varying demands depending on the material combinations, all of the tank regions that are critical to structural stability passed the ACI 349-06 acceptance criteria. This was true for the conservative combination of maximum recorded thermal loads and maximum soil overburden depth combined with the analysis matrix of bounding material property combinations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Local Structure of Glassy Lithium Phosphorus Oxynitride Thin Films: A Combined Experimental and Ab Initio Approach

Abstract Lithium phosphorus oxynitride (LiPON) is an amorphous solid‐state lithium ion conductor displaying exemplary cyclability against lithium metal anodes. There is no definitive explanation for this stability due to the limited understanding of the structure of LiPON. Herein, we provide a structural model of RF‐sputtered LiPON. Information about the short‐range structure results from 1D and 2D solid‐state NMR experiments. These results are compared with first principles chemical shielding calculations of Li‐P‐O/N crystals and ab initio molecular dynamics‐generated amorphous LiPON models to unequivocally identify the glassy structure as primarily isolated phosphate monomers with N incorporated in both apical and as bridging sites in phosphate dimers. Structural results suggest LiPON′s stability is a result of its glassy character. Free‐standing LiPON films are produced that exhibit a high degree of flexibility, highlighting the unique mechanical properties of glassy materials.

Marple, Maxwell A. T.↗