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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Understanding the Mechanism of Secondary Cation Release from the (001) Surface of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 : Insights from First-Principles

The transformations of complex metal oxides in aqueous settings must be studied to form a chemical understanding of how technologically relevant nanomaterials impact the environment upon disposal. Owing to the inherent heterogeneity and structural complexity of the ternary intercalation material Li(Ni x Mn y Co 1-x-y )O 2 (NMC), the mechanisms of chemical processes at the solid–water interfac e are challenging to model. Here, density functional theory (DFT) + solvent ion methodology is used to study the energetics of stepwise release of two surface metals following unique pathways. Further, the study spans different combinations of metal removal and also considers unique patterns of defects formed by modeling the NMC surface in supercells. The approach here also considers the equilibration of the surface with the surroundings between successive metal removals. A key finding is that a second metal removal prefers to proceed at a metal lattice site adjacent to the initial defect, and this is attributed in part to how the resulting slab with two metal vacancies maintains the most antiferromagnetic couplings between the remaining Ni/Mn.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Consideration of the Aluminum Distribution in Zeolites in Theoretical and Experimental Catalysis Research

Research efforts in zeolite catalysis have become increasingly cognizant of the diversity in structure and function resulting from the distribution of framework aluminum atoms, through emerging reports of catalytic phenomena that fall outside those recognizable as the shape-selective ones emblematic of its earlier history. Molecular-level descriptions of how active-site distributions affect catalysis are an aspirational goal articulated frequently in experimental and theoretical research, yet they are limited by imprecise knowledge of the structure and behavior of the zeolite materials under interrogation. In experimental research, higher precision can result from more reliable control of structure during synthesis and from more robust and quantitative structural and kinetic characterization probes. In theoretical research, construction of models with specific aluminum locations and distributions seldom capture the heterogeneity inherent to the materials studied by experiment. In this Perspective, we discuss research findings that appropriately frame the challenges in developing more predictive synthesis-structure-function relations for zeolites, highlighting studies on ZSM-5 zeolites that are among the most structurally complex molecular sieve frameworks and the most widely studied because of their versatility in commercial applications. We discuss research directions to address these challenges and forge stronger connections between zeolite structure, composition, and active sites to catalytic function. Such connections promise to aid in bridging the findings of theoretical and experimental catalysis research, and transforming zeolite active site design from an empirical endeavor into a more predictable science founded on validated models.

09 BIOMASS FUELS↗
DOE OSTI2021

Thermodynamics of order and randomness in dopant distributions inferred from atomically resolved imaging

Abstract Exploration of structure-property relationships as a function of dopant concentration is commonly based on mean field theories for solid solutions. However, such theories that work well for semiconductors tend to fail in materials with strong correlations, either in electronic behavior or chemical segregation. In these cases, the details of atomic arrangements are generally not explored and analyzed. The knowledge of the generative physics and chemistry of the material can obviate this problem, since defect configuration libraries as stochastic representation of atomic level structures can be generated, or parameters of mesoscopic thermodynamic models can be derived. To obtain such information for improved predictions, we use data from atomically resolved microscopic images that visualize complex structural correlations within the system and translate them into statistical mechanical models of structure formation. Given the significant uncertainties about the microscopic aspects of the material’s processing history along with the limited number of available images, we combine model optimization techniques with the principles of statistical hypothesis testing. We demonstrate the approach on data from a series of atomically-resolved scanning transmission electron microscopy images of Mo x Re 1- x S 2 at varying ratios of Mo/Re stoichiometries, for which we propose an effective interaction model that is then used to generate atomic configurations and make testable predictions at a range of concentrations and formation temperatures.

25 ENERGY STORAGE↗
DOE OSTI2019

Improved Modeling of Peptide-Protein Binding Through Global Docking and Accelerated Molecular Dynamics Simulations

We find that peptides mediate up to 40% of known protein-protein interactions in higher eukaryotes and play a key role in cellular signaling, protein trafficking, immunology, and oncology. However, it is challenging to predict peptide-protein binding with conventional computational modeling approaches, due to slow dynamics and high peptide flexibility. Here, we present a prototype of the approach which combines global peptide docking using ClusPro PeptiDock and all-atom enhanced simulations using Gaussian accelerated molecular dynamics (GaMD). For three distinct model peptides, the lowest backbone root-mean-square deviations (RMSDs) of their bound conformations relative to X-ray structures obtained from PeptiDock were 3.3–4.8 Å, being medium quality predictions according to the Critical Assessment of PRediction of Interactions (CAPRI) criteria. GaMD simulations refined the peptide-protein complex structures with significantly reduced peptide backbone RMSDs of 0.6–2.7 Å, yielding two high quality (sub-angstrom) and one medium quality models. Furthermore, the GaMD simulations identified important low-energy conformational states and revealed the mechanism of peptide binding to the target proteins. Therefore, PeptiDock+GaMD is a promising approach for exploring peptide-protein interactions.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2007

Microbial Extremophiles in Aspect of Limits of Life

During Earth's evolution accompanied by geophysical and climatic changes a number of ecosystems have been formed. These ecosystems differ by the broad variety of physicochemical and biological factors composing our environment. Traditionally, pH and salinity are considered as geochemical extremes, as opposed to the temperature, pressure and radiation that are referred to as physical extremes (Van den Burg, 2003). Life inhabits all possible places on Earth interacting with the environment and within itself (cross species relations). In nature it is very rare when an ecotope is inhabited by a single species. As a rule, most ecosystems contain the functionally related and evolutionarily adjusted communities (consortia and populations). In contrast to the multicellular structure of eukaryotes (tissues, organs, systems of organs, whole organism), the highest organized form of prokaryotic life in nature is the benthic colonization in biofilms and microbial mats. In these complex structures all microbial cells of different species are distributed in space and time according to their functions and to physicochemical gradients that allow more effective system support, self-protection, and energy distribution. In vitro, of course, the most primitive organized structure for bacterial and archaeal cultures is the colony, the size, shape, color, consistency, and other characteristics of which could carry varies specifics on species or subspecies levels. In table 1 all known types of microbial communities are shown (Pikuta et a]., 2005). In deep underground (lithospheric) and deep-sea ecosystems an additional factor - pressure, and irradiation - could also be included in the list of microbial communities. Currently the beststudied ecosystems are: human body (due to the medical importance), and fresh water and marine ecosystems (due to the reason of an environmental safety). For a long time, extremophiles were terra incognita, since the environments with aggressive parameters (compared to the human body temperature, pH, mineralization, and pressure) were considered a priori as a dead zone.

Pikuta, Elena V.↗
NASA NTRS1985

Ultraviolet interstellar absorption toward stars in the Small Magellanic Cloud. III - The structure and kinematics of the Small Magellanic Cloud

The structural and kinematic properties of the Small Magellanic Cloud (SMC) were studied by combining IUE satellite observations of individual bright stars (Sk 159 and HD 5980) with existing optical and radio data. It is shown that the SMC has a complex structure due to gravitational interaction with the Milky Way and the Large Magellanic Cloud (LMC). Stars observed in the southwest regions of the SMC were associated with the 134 km/s H I complex. H II regions in the SMC were distributed according to a rotational velocity of 167 km/s. All IUE high-dispersion targets exhibit ultraviolet absorption near 100 km/s and 200 km/s. It is shown that the absorption arises in the widespread H I complexes at velocities similar to the H II regions. Some possible explanations for the origin of H II and H I regions in the SMC are discussed. The locations of the nine high-dispersion IUE targets in the SMC are given.

Fitzpatrick, E. L.↗
DOE OSTI2015

Tuning the Electronic Structure of Anatase Through Fluorination

A highly fluorinated anatase lattice has been recently reported, providing a new class of materials whose general chemical formula is T i1-x $\square$ x X 4x O 2-4x (X - = F - or OH - ). To characterise the complex structural features of the material and the different F environments, we here apply a computational screening procedure. After deriving a polarisable force—field from DFT simulations, we screen in a step-wise fashion a large number of possible configurations differing in the positioning of the titanium vacancies ($\square$) and of the fluorine atoms. At each step only 10% of the configurations are retained. At the end of the screening procedure, a configuration is selected and simulated using DFT-based molecular dynamics. This allows us to analyse the atomic structure of the material, which is strongly disordered, leading to a strong decrease (by 0.8 eV) of the band gap compared to conventional anatase.

Science & Technology - Other Topics↗
DOE OSTI2017

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Local and teleseismic earthquake waveforms recorded by a 180-m-long linear array (BB) with seven seismometers crossing the Clark fault of the San Jacinto fault zone northwest of Anza are used to image a deep bimaterial interface and core damage structure of the fault. Delay times of P waves across the array indicate an increase in slowness from the southwest most (BB01) to the northeast most (BB07) station. Automatic algorithms combined with visual inspection and additional analyses are used to identify local events generating fault zone head and trapped waves. The observed fault zone head waves imply that the Clark fault in the area is a sharp bimaterial interface, with lower seismic velocity on the southwest side. The moveout between the head and direct P arrivals for events within ~40 km epicentral distance indicates an average velocity contrast across the fault over that section and the top 20 km of 3.2 per cent. A constant moveout for events beyond ~40 km to the southeast is due to off-fault locations of these events or because the imaged deep bimaterial interface is discontinuous or ends at that distance. The lack of head waves from events beyond ~20 km to the northwest is associated with structural complexity near the Hemet stepover. Events located in a broad region generate fault zone trapped waves at stations BB04–BB07. Waveform inversions indicate that the most likely parameters of the trapping structure are width of ~200 m, S velocity reduction of 30–40 per cent with respect to the bounding blocks, Q value of 10–20 and depth of ~3.5 km. The trapping structure and zone with largest slowness are on the northeast side of the fault. The observed sense of velocity contrast and asymmetric damage across the fault suggest preferred rupture direction of earthquakes to the northwest. This inference is consistent with results of other geological and seismological studies.

58 GEOSCIENCES↗
NASA NTRS2000

Application of the Spectral Element Method to Acoustic Radiation

This report summarizes research to develop a capability for analysis of interior noise in enclosed structures when acoustically excited by an external random source. Of particular interest was the application to the study of noise and vibration transmission in thin-walled structures as typified by aircraft fuselages. Three related topics are focused upon. The first concerns the development of a curved frame spectral element, the second shows how the spectral element method for wave propagation in folded plate structures is extended to problems involving curved segmented plates. These are of significance because by combining these curved spectral elements with previously presented flat spectral elements, the dynamic response of geometrically complex structures can be determined. The third topic shows how spectral elements, which incorporate the effect of fluid loading on the structure, are developed for analyzing acoustic radiation from dynamically loaded extended plates.

Doyle, James F.↗
NASA NTRS2006

The 3D Structure of Eta Carinae's Nebula: A Definitive Picture from High-Dispersion Near-IR Spectra

High resolution long-slit spectra obtained with the Phoenix spectrograph on Gemini South provide our most accurate probe of the 3D structure of the Homunculus Nebula around Eta Carinae. Emission from molecular hydrogen at 2.122 microns traces a very thin outer skin, which contains the vast majority of the more than 10 solar masses of material in the nebula. This emission, in turn, yields our first definitive picture of the exact shape of the nebula, plus the latitude dependence of the mass-loss rate, speed, kinetic energy, shell thickness, and other properties associated with Eta Car's 19th century explosion. This will be critical for testing any models for the outburst mechanism. A preliminary analysis suggests that explosion from a critically rotating star was the dominant mechanism that gave rise to both the bipolar shape of the nebula and the production of its equatorial disk. [Fe II] emission in the near IR traces a geometrically thicker but less massive shell found on the inner surface of the H2 skin --- this is either a reverse shock that decelerates Eta Car's wind or a warm PDR. [Fe Ill emission also clarifies the structure of an inner "Little Homunculus" seen previously in HST/STlS spectra. Comparing these two tracers of cool molecular gas and warm partially-ionized gas resolves some significant confusion about the complex structure noted in previous studies.

Smith, N.↗
NASA NTRS1994

Associated with aerospace vehicles development of methodologies for the estimation of thermal properties

Thermal stress analyses are an important aspect in the development of aerospace vehicles at NASA-LaRC. These analyses require knowledge of the temperature distributions within the vehicle structures which consequently necessitates the need for accurate thermal property data. The overall goal of this ongoing research effort is to develop methodologies for the estimation of the thermal property data needed to describe the temperature responses of these complex structures. The research strategy undertaken utilizes a building block approach. The idea here is to first focus on the development of property estimation methodologies for relatively simple conditions, such as isotropic materials at constant temperatures, and then systematically modify the technique for the analysis of more and more complex systems, such as anisotropic multi-component systems. The estimation methodology utilized is a statistically based method which incorporates experimental data and a mathematical model of the system. Several aspects of this overall research effort were investigated during the time of the ASEE summer program. One important aspect involved the calibration of the estimation procedure for the estimation of the thermal properties through the thickness of a standard material. Transient experiments were conducted using a Pyrex standard at various temperatures, and then the thermal properties (thermal conductivity and volumetric heat capacity) were estimated at each temperature. Confidence regions for the estimated values were also determined. These results were then compared to documented values. Another set of experimental tests were conducted on carbon composite samples at different temperatures. Again, the thermal properties were estimated for each temperature, and the results were compared with values obtained using another technique. In both sets of experiments, a 10-15 percent off-set between the estimated values and the previously determined values was found. Another effort was related to the development of the experimental techniques. Initial experiments required a resistance heater placed between two samples. The design was modified such that the heater was placed on the surface of only one sample, as would be necessary in the analysis of built up structures. Experiments using the modified technique were conducted on the composite sample used previously at different temperatures. The results were within 5 percent of those found using two samples. Finally, an initial heat transfer analysis, including conduction, convection and radiation components, was completed on a titanium sandwich structural sample. Experiments utilizing this sample are currently being designed and will be used to first estimate the material's effective thermal conductivity and later to determine the properties associated with each individual heat transfer component.

Scott, Elaine P.↗
DOE OSTI2016

Modular Homogeneous Chromophore–Catalyst Assemblies

Photosynthetic reaction center (RC) proteins convert incident solar energy to chemical energy through a network of molecular cofactors which have been evolutionarily tuned to couple efficient light-harvesting, directional electron transfer, and long-lived charge separation with secondary reaction sequences. These molecular cofactors are embedded within a complex protein environment which precisely positions each cofactor in optimal geometries along efficient electron transfer pathways with localized protein environments facilitating sequential and accumulative charge transfer. By contrast, it is difficult to approach a similar level of structural complexity in synthetic architectures for solar energy conversion. However, by using appropriate self-assembly strategies, we anticipate that molecular modules, which are independently synthesized and optimized for either light-harvesting or redox catalysis, can be organized into spatial arrangements that functionally mimic natural photosynthesis. In this Account, we describe a modular approach to new structural designs for artificial photosynthesis which is largely inspired by photosynthetic RC proteins. We focus on recent work from our lab which uses molecular modules for light-harvesting or proton reduction catalysis in different coordination geometries and different platforms, spanning from discrete supramolecular assemblies to molecule–nanoparticle hybrids to protein-based biohybrids. Molecular modules are particularly amenable to high-resolution characterization of the ground and excited state of each module using a variety of physical techniques; such spectroscopic interrogation helps our understanding of primary artificial photosynthetic mechanisms. In particular, we discuss the use of transient optical spectroscopy, EPR, and X-ray scattering techniques to elucidate dynamic structural behavior and light-induced kinetics and the impact on photocatalytic mechanism. Two different coordination geometries of supramolecular photocatalyst based on the [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) light-harvesting module with cobaloxime-based catalyst module are compared, with progress in stabilizing photoinduced charge separation identified. These same modules embedded in the small electron transfer protein ferredoxin exhibit much longer charge-separation, enabled by stepwise electron transfer through the native [2Fe-2S] cofactor. We anticipate that the use of interchangeable, molecular modules which can interact in different coordination geometries or within entirely different structural platforms will provide important fundamental insights into the effect of environment on parameters such as electron transfer and charge separation, and ultimately drive more efficient designs for artificial photosynthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

The electronic states of TeH{sup +}: A theoretical contribution

This work reports the first theoretical characterization of a manifold of electronic states of the as yet experimentally unknown monotellurium monohydride cation, TeH{sup +}. Both Λ + S and Ω representations were described showing the twelve states correlating with the three lowest (Λ + S) dissociation channels, and the twenty five states associated with the five lowest Ω channels. The X {sup 3}Σ{sup −} state is split into X{sub 1} 0{sup +} and X{sub 2} 1 separated by 1049 cm{sup −1}; they are followed by the states a 2 (a {sup 1}Δ) and b 0{sup +} (b {sup 1}Σ{sup +}) higher in energy by 8554 and 17 383 cm{sup −1}, respectively. These states can accommodate several vibrational energy levels. The potential energy curves of the Ω states arising from the bound A {sup 3}Π, the weakly bound {sup 1}Π, and the repulsive {sup 5}Σ{sup −} states have a complex structure as shown by the very close avoided crossings just above ∼30 000 cm{sup −1}. In particular, a double minima potential results for the state A{sub 1} 2 that in principle could be probed experimentally through the A{sub 1} 2–X{sub 2} 1 system transitions. The states A{sub 2} 1, b 0{sup +}, and A{sub 4} 0{sup +} offer possible routes to experimental investigations involving the ground state X{sub 1} 0{sup +}. Higher energy states are very dense and mostly repulsive. The high-level of the electronic structure calculations, by providing a global view of the electronic states and reliable spectroscopic parameters, is expected to further guide and motivate experimental studies on this species. Additional discussions on dipole and transition dipole moments, transition probabilities, radiative lifetimes, and a simulation of the single ionization spectrum complement the characterization of this system.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Nonclassical Strong Metal–Support Interactions for Enhanced Catalysis

Strong metal–support interaction (SMSI), which encompasses reversible encapsulation and de-encapsulation and modulation of surface adsorption properties, imposes great impacts on the performance of heterogeneous catalysts. Recent development of SMSI has surpassed the prototypical encapsulated Pt-TiO 2 catalyst, affording a series of conceptually novel and practically advantageous catalytic systems. Here, in this work, we provide our perspective on recent progress in nonclassical SMSIs for enhanced catalysis. Unravelling the structural complexity of SMSI necessitates the combination of multiple characterization techniques at different scales. Synthesis strategies leveraging chemical, photonic, and mechanochemical driving forces further expand the definition and application scope of SMSI. Exquisite structure engineering permits elucidation of the interface, entropy, and size effect on the geometric and electronic characteristics. Materials innovation places the atomically thin two-dimensional materials at the forefront of interfacial active site control. A broader space is awaiting exploration, where exploitation of metal–support interactions brings compelling catalytic activity, selectivity, and stability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Framework Short-Range Order Observed in a Spinel-Type Li Superionic Conductor

Solid-state superionic conductors are characterized by rich structural disorders. Though structural complexities are central to their functionalities, they often give rise to short-range order that eludes detection by conventional diffraction-based techniques and is thus overlooked in establishing precise structure-property relationships. In this work, we synthesized single crystals of a recently discovered lithium (Li) superionic conductor Li16.2(1)In9.00(2)Sn1.10(1)O23.8 (LISO) for in-depth characterizations of structural subtleties. LISO exhibits an unusual spinel-like phase with significant Li overstoichiometry and a face-sharing Li network. Single-crystal neutron diffraction confirms significant Li disorder, as manifested in Li site splitting and partial occupancy. More importantly, synchrotron diffuse scattering combined with 3D-ΔPDF analysis and Monte Carlo simulations reveal short-range order in the nonalkali framework that might contribute to the phase stability and ionic conductivity. This work showcases an example in which subtle local energetics can be directly visualized in structurally disordered ionic conductors.

Chen, Yu↗
DOE OSTI2024

Characterizing structural features of two-dimensional particle systems through Voronoi topology

This paper introduces a new approach toward characterizing local structural features of two-dimensional particle systems. The approach can accurately identify and characterize defects in high-temperature crystals, distinguish a wide range of nominally disordered systems, and robustly describe complex structures such as grain boundaries. This paper also introduces two-dimensional functionality into the open-source software program VoroTop which automates this analysis. This software package is built on a recently-introduced multithreaded version of V ORO ++, enabling the analysis of systems with billions of particles on high-performance computer architectures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Understanding High-Voltage Behavior of Sodium-Ion Battery Cathode Materials Using Synchrotron X-ray and Neutron Techniques: A Review

Despite substantial research efforts in developing high-voltage sodium-ion batteries (SIBs) as high-energy-density alternatives to complement lithium-ion-based energy storage technologies, the lifetime of high-voltage SIBs is still associated with many fundamental scientific questions. In particular, the structure phase transition, oxygen loss, and cathode–electrolyte interphase (CEI) decay are intensely discussed in the field. Synchrotron X-ray and neutron scattering characterization techniques offer unique capabilities for investigating the complex structure and dynamics of high-voltage cathode behavior. In this review, to accelerate the development of stable high-voltage SIBs, we provide a comprehensive and thorough overview of the use of synchrotron X-ray and neutron scattering in studying SIB cathode materials with an emphasis on high-voltage layered transition metal oxide cathodes. We then discuss these characterizations in relation to polyanion-type cathodes, Prussian blue analogues, and organic cathode materials. Finally, future directions of these techniques in high-voltage SIB research are proposed, including CEI studies for polyanion-type cathodes and the extension of neutron scattering techniques, as well as the integration of morphology and phase characterizations.

25 ENERGY STORAGE↗
NASA NTRS1973

Automated sizing of large structures by mixed optimization methods

A procedure for automating the sizing of wing-fuselage airframes was developed and implemented in the form of an operational program. The program combines fully stressed design to determine an overall material distribution with mass-strength and mathematical programming methods to design structural details accounting for realistic design constraints. The practicality and efficiency of the procedure is demonstrated for transport aircraft configurations. The methodology is sufficiently general to be applicable to other large and complex structures.

Sobieszczanski, J.↗