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At least 973 records · Page 54

Solar Photovaltaics Durability and Resilience - A Win-Win

Solar photovoltaics (PV) will play a crucial role in decarbonizing the electrical grid and limit the effects of detrimental climate change. Long lifetimes of PV installations are a win-win situation, as it not only reduces carbon emissions directly through avoidance of fossil fuel emissions but also indirectly, as it reduces the demand of needed materials and potentially recycling. However, during their decades-long lifetime expectations installations are also more commonly exposed to extreme weather events. Building durable solar system to withstand extreme weather events is essential in the electrification of the economy and will save lives, particularly when they power critical infrastructure such as hospitals. As more PV is installed in regions prone to extreme weather events, high-quality materials, installation and monitoring practices can mitigate risk. Evaluating resilience requires combined computational, analytical, and experimental capabilities that are best leveraged by teams working across multiple disciplines.

durability↗

Redox-stable symmetrical solid oxide fuel cells with exceptionally high performance enabled by electrode/electrolyte diffuse interface

Here, in this study, we report a high performance and redox-stable symmetrical solid oxide fuel cell (SOFC) based on (Ba 0.5 Sr 0.5 ) (Mo 0.1 Fe 0.9 )O 3-δ (BSMF) electrode and La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ (LSGM) electrolyte. BSMF is able to operate both as anode and cathode. Excellent electrocatalytic activity has been achieved on BSMF towards hydrogen oxidation and oxygen reduction. Due to its closely matched lattice parameter to LSGM electrolyte, a unique diffuse interface is formed between BSMF and LSGM. Compared to a clean interface, e.g. BSMF/gadolinium doped ceria interface, this diffuse interface promotes the performance of BSMF electrode 1–1.8 times in 600–800 °C. Polarization resistance of the BSMF/LSGM specimen is as low as 0.047 and 0.007 Ωcm 2 in humidified H 2 and in air at 800 °C, respectively. On the BSMF/LSGM/BSMF symmetrical cell, a maximum power density of 2.28 W/cm 2 is achieved at 800 °C, the highest among with redox-stable ceramic electrodes to the best of our knowledge. Redox stability of this cell is confirmed. The role of anode and cathode is reversed back and forth in different operation modes. No apparent degradation is observed through 4 cycles within a 110 h operation period. These findings demonstrate that (Ba 0.5 Sr 0.5 ) (M o0.1 Fe 0.9 )O 3-δ coupled with LSGM electrolyte is an excellent choice to build a high performance, redox-stable SOFC.

25 ENERGY STORAGE↗

Flux growth of a new cobalt-zinc-tin ternary phase Co{sub 7+x}Zn{sub 3-x}Sn{sub 8} and its relationship to CoSn

The intermetallic compound Co{sub 7+x}Zn{sub 3-x}Sn{sub 8} (-0.2<x<0.2) forms from the reaction of cobalt in zinc/tin eutectic flux. This phase has a new structure type in orthorhombic space group Cmcm, with unit cell parameters a=4.138(1) A, b=12.593(4) A, and c=11.639(4) A (Z=2; R{sub 1}=0.0301). Varying the amount of cobalt in the synthesis leads to formation of a superstructure in space group Pnma, with lattice parameters a=12.5908(2) A, b=11.6298(3) A, and c=8.2704(2) A (Z=4; R{sub 1}=0.0347). A Co/Zn mixed site and a partially occupied Co site in the Cmcm structure order to form the Pnma supercell. TGA/DSC studies indicate that the binary phase CoSn initially forms in the flux at 1173 K, and then reacts with the zinc in the cooling solution to form the ternary structure at 823 K. This phase exhibits Pauli paramagnetic behavior. - Graphical abstract: Co{sub 7+x}Zn{sub 3-x}Sn{sub 8} forms from the reaction of cobalt in zinc/tin eutectic flux; it exhibits a Cmcm subcell or Pnma supercell depending on reactant stoichiometry. Highlights: > Co{sub 7+x}Zn{sub 3-x}Sn{sub 8} grows from reaction of cobalt in Zn/Sn eutectic flux. > Varying Co in reaction stoichiometry yields Cmcm subcell or Pnma supercell structure. > Co{sub 7+x}Zn{sub 3-x}Sn{sub 8} structural building blocks similar to those in CoSn binary phase. > Co{sub 7+x}Zn{sub 3-x}Sn{sub 8} forms from reaction of CoSn in the Zn/Sn flux.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Two new coordination polymers constructed by naphthalene-1,4-dicarboxylic acid and 2,4-diamino-6-methyl-triazine

Two new transition metal coordination complexes, ([MnO(nda)](H{sub 2}dmt)(H{sub 2}O)){sub n} (1), [Ag{sub 5}(nda){sub 2.5}(dmt)]{sub n} (2), (H{sub 2}nda=naphthalene-1,4-dicarboxylic acid, dmt=2,4-diamine-6-methyl-1,3,5-triazine) have been hydrothermally synthesized by the reactions of H{sub 2}nda and dmt with the homologous MnCl{sub 2}·4H{sub 2}O and AgNO{sub 3}, respectively, and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, thermogravimetric analysis (TGA). The compound 1 exhibits a 3D network comprising 1D metal chain (MnO(CO{sub 2}){sub 2}){sub n} connected by the ligand nda{sup 2−}, featuring a four-connected uninodal diamond -like topology. In compound 2, it is firstly observed that decanuclear silver units as secondary building units to construct 3D network by the ligands dmt and nda{sup 2−}, with a rare 2-nodal (3,8)-connected tfz-d topology ((4{sup 3}){sub 2}(4{sup 6}.6{sup 18}.8{sup 4})). The interactions within each Mn(II)—Mn(II) pair of compound 1 are antiferromagnetic (g=2.07, J=−1.42(1) cm{sup −1}, zj′=−0.73(2) cm{sup −1}). In addition, compound 2 exhibits photoluminescent property at about 472 nm (λ{sub ex}=394 nm). - Graphical abstract: Two new transition metal coordination complexes 1–2 have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis thermogravimetric analysis (TGA). Highlights: • The compound 1 exhibits a 3D network with four-connected uninodal diamond-like topology. • The first 3D network of 2 with a rare tfz-d topology consists of decanuclear silver clusters as secondary building units. • The magnetic measurement indicates the compound 1 shows antiferromagnetic interactions. • The photoluminescent property of 2 has been measured.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Syntheses and structures of three heterometallic coordination polymers derived from 4-pyridin-3-yl-benzoic acid

Three lanthanide–transition-metal coordination polymers, namely, [Er{sub 2}L{sub 6}(H{sub 2}O)][Cu{sub 2}I{sub 2}] (1), [ErL{sub 3}][CuI] (2), and [Dy{sub 2}L{sub 6}(BPDC){sub 0.5}(H{sub 2}O){sub 4}][Cu{sub 3}I{sub 2}] (3) (HL=4-pyridin-3-yl-benzoic acid, H{sub 2}BPDC=4,4′-biphenyldicarboxylic acid) have been made by reacting Ln{sub 2}O{sub 3} and CuI with HL at different temperatures under hydrothermal conditions. All the complexes are characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction, respectively. 1–3 all construct from dimeric (Ln{sub 2}) and (Cu{sub 2}) units and exhibit two types of the structural features: 1 is a two-dimensional layer, 2–3 are three-dimensional frameworks. Interestingly, the in situ formation of the BPDC ligand is found in the structure of 3. The distinct architectures of these complexes indicated that the reaction temperature plays an important role in the formation of higher dimensional coordination polymers. - Graphical abstract: By hydrothermal reaction of lanthanide oxide, copper halide, and 4-pyridin-3-yl-benzoic ligand at different temperatures, a series of 1-D to 3-D 3d–4f coordination polymers, namely [ErL{sub 3}(H{sub 2}O){sub 2}][CuI], [Er{sub 2}L{sub 6}(H{sub 2}O)][Cu{sub 2}I{sub 2}], [ErL{sub 3}][CuI], and [Dy{sub 2}L{sub 6}(BPDC){sub 0.5}(H{sub 2}O){sub 4}][Cu{sub 3}I{sub 2}], have been made, respectively. - Highlights: • Three novel heterometallic coordination polymers derived from 4-pyridin-3-yl-benzoic acid have been hydrothermally synthesized. • Mixed dinuclear motifs of (Ln{sub 2}) and (Cu{sub 2}) serve as secondary building units to generate 2-D layer and 3-D frameworks. • It is proved that higher temperature is apt to permit construction of high dimensional architectures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Cooperative Electronic and Structural Regulation in a Bioinspired Allosteric Photoredox Catalyst

Here in this article, we report the first allosteric photoredox catalyst regulated via constructively coupled structural and electronic control. While often synergistically exploited in nature, these two types of control mechanisms have only been applied independently in the vast majority of allosteric enzyme mimics and receptors in the literature. By embedding a model of photosystem II in a supramolecular coordination complex that responds to chloride as an allosteric effector, we show that distance and electronic control of light harvesting can be married to maximize allosteric regulation of catalytic activity. This biomimetic system is composed of a Bodipy photoantenna, which is capable of transferring excited-state energy to a photoredox pair, wherein the excitation energy is used to generate a catalytically active charge-separated state. The structural aspect of allosteric regulation is achieved by toggling the coordination chemistry of an antenna-functionalized hemilabile ligand via partial displacement from a Rh I structual node using chloride. In doing so, the distance between the antenna and the central photoredox catalyst is increased, lowering the inherent efficiency of through-space energy transfer. At the same time, coordination of chloride lowers both the charge of the Rh I node and the reduction potential of the Rh II/I couple, to the extent that electronic quenching of the antenna excited state is possible via photoinduced electron transfer from the metal center. Compared to a previously developed system that operates solely via electronic regulation, the present system demonstrates that coupling electronic and structural approaches to allosteric regulation gives rise to improved switching ratios between catalytically active and inactive states. Contributions from both structural and electronic control mechanisms are probed via nuclear magnetic resonance, X-ray diffraction, electrochemical, spectroelectrochemical, and transient absorption studies. Overall, this work establishes that intertwined electronic and structural regulatory mechanisms can be borrowed from nature to build stimuli-responsive inorganic materials with potential applications in sensing, catalysis, and photonic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Identification of phases, symmetries and defects through local crystallography

Here we report that advances in electron and probe microscopies allow 10 pm or higher precision in measurements of atomic positions. This level of fidelity is sufficient to correlate the length (and hence energy) of bonds, as well as bond angles to functional properties of materials. Traditionally, this relied on mapping locally measured parameters to macroscopic variables, for example, average unit cell. This description effectively ignores the information contained in the microscopic degrees of freedom available in a high-resolution image. Here we introduce an approach for local analysis of material structure based on statistical analysis of individual atomic neighbourhoods. Clustering and multivariate algorithms such as principal component analysis explore the connectivity of lattice and bond structure, as well as identify minute structural distortions, thus allowing for chemical description and identification of phases. This analysis lays the framework for building image genomes and structure–property libraries, based on conjoining structural and spectral realms through local atomic behaviour.

36 MATERIALS SCIENCE↗

Synthesis and structural characterization of the new clathrates K 8 Cd 4 Ge 42 , Rb 8 Cd 4 Ge 42 , and Cs 8 Cd 4 Ge 42

This paper presents results from our exploratory work in the systems K-Cd-Ge, Rb-Cd-Ge, and Cs-Cd-Ge, which yielded the novel type-I clathrates with refined compositions K 8 Cd 3.77(7) Ge 42.23 , Rb 8 Cd 3.65(7) Ge 42.35 , and Cs 7.80(1) Cd 3.65(6) Ge 42.35 . The three compounds represent rare examples of clathrates of germanium with the alkali metals, where a d 10 element substitutes a group 14 element. The three structures, established by single-crystal X-ray diffraction, indicate that the framework-building Ge atoms are randomly substituted by Cd atoms on only one of the three possible crystallographic sites. Furthermore, this and several other details of the crystal chemistry are elaborated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

A Machine Learning Approach for the Discovery of Ligand-Specific Functional Mechanisms of GPCRs

G protein-coupled receptors (GPCRs) play a key role in many cellular signaling mechanisms, and must select among multiple coupling possibilities in a ligand-specific manner in order to carry out a myriad of functions in diverse cellular contexts. Much has been learned about the molecular mechanisms of ligand-GPCR complexes from Molecular Dynamics (MD) simulations. However, to explore ligand-specific differences in the response of a GPCR to diverse ligands, as is required to understand ligand bias and functional selectivity, necessitates creating very large amounts of data from the needed large-scale simulations. This becomes a Big Data problem for the high dimensionality analysis of the accumulated trajectories. Here we describe a new machine learning (ML) approach to the problem that is based on transforming the analysis of GPCR function-related, ligand-specific differences encoded in the MD simulation trajectories into a representation recognizable by state-of-the-art deep learning object recognition technology. We illustrate this method by applying it to recognize the pharmacological classification of ligands bound to the 5-HT 2A and D2 subtypes of class-A GPCRs from the serotonin and dopamine families. The ML-based approach is shown to perform the classification task with high accuracy, and we identify the molecular determinants of the classifications in the context of GPCR structure and function. This study builds a framework for the efficient computational analysis of MD Big Data collected for the purpose of understanding ligand-specific GPCR activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Immersive Visualization for Materials Science Data Analysis using the Oculus Rift

In this paper, we propose strategies and objectives for immersive data visualization with applications in materials science using the Oculus Rift virtual reality headset. We provide background on currently available analysis tools for neutron scattering data and other large-scale materials science projects. In the context of the current challenges facing scientists, we discuss immersive virtual reality visualization as a potentially powerful solution. We introduce a prototype immersive visual- ization system, developed in conjunction with materials scientists at the Spallation Neutron Source, which we have used to explore large crystal structures and neutron scattering data. Finally, we offer our perspective on the greatest challenges that must be addressed to build effective and intuitive virtual reality analysis tools that will be useful for scientists in a wide range of fields.

analytics↗

AMRZone: A Runtime AMR Data Sharing Framework For Scientific Applications

Frameworks that facilitate runtime data sharing across multiple applications are of great importance for scientific data analytics. Although existing frameworks work well over uniform mesh data, they can not effectively handle adaptive mesh refinement (AMR) data. Among the challenges to construct an AMR-capable framework include: (1) designing an architecture that facilitates online AMR data management; (2) achieving a load-balanced AMR data distribution for the data staging space at runtime; and (3) building an effective online index to support the unique spatial data retrieval requirements for AMR data. Towards addressing these challenges to support runtime AMR data sharing across scientific applications, we present the AMRZone framework. Experiments over real-world AMR datasets demonstrate AMRZone's effectiveness at achieving a balanced workload distribution, reading/writing large-scale datasets with thousands of parallel processes, and satisfying queries with spatial constraints. Moreover, AMRZone's performance and scalability are even comparable with existing state-of-the-art work when tested over uniform mesh data with up to 16384 cores; in the best case, our framework achieves a 46% performance improvement.

Zhang, Wenzhao↗

Light Initiated High Explosive Driven Flyer Plate Impulse Generation Technique For Material and Structural Response

The objective for this research has been to develop a method to induce a high frequency, large amplitude shock pulse into materials and structures as an above-ground laboratory simulation of an exo-atmospheric cold x-ray induced blow-off event. This work builds on the successes of direct-spray Light Initiated High Explosive impulse delivery technique, in order to drive a flyer to a desired impact velocity to induce the proper combined material and structural response of the target. The reported development focuses on flyer velocity from explosive initiation to target impact to flyer rebound. A comprehensive derivation of an analytical model to predict flyer velocity as a function of explosive deposition and flyer properties is presented. One-and two-dimensional test series were conducted to evaluate impulse delivery and impact pressure, as well as target material and structural response. Experimental results show good agreement in flyer velocity between that predicted by the developed theory and that inferred by impulse delivery. A definitive material response was measured in each of the one-dimensional targets. The structural strain response measured in the ring experiments showed excellent agreement with both the predicted flyer performance and the analytical strain solution for a cosine distributed impulsive loading. This work has focused on the utilization of analytical, hydrocode, and test analysis to confirm that a LIHE driven flyer impulse technique can be an effective simulation of a cold x-ray blow-off event. It is shown that a thin metallic flyer plate can be explosively accelerated to impact a target with sufficient energy to generate an impulsive load which induces both structural and material response in a test item.

36 MATERIALS SCIENCE↗

Imagery Applications for Advanced Event Analytics (WBS 24.3.1.3.3-IDC FY202 Final Project Report)

Accurate event locations and replicability of location analyses are essential for assessing the nature of an event, its context, ambient site conditions, and proximity to relevant facilities and infrastructure. Additionally, accurate event locations provide valuable information that reduce uncertainties, improve confidence in event analyses, and inform in-field verification activities. However, event location/relocation and replicability are difficult due to a number of factors, including spatially-sparse network coverage in some areas of the globe and variability in seismic data processing. This team proposed that the incorporation of high-fidelity imagery as a data backbone to the analytical assessment of a suspected underground explosion and/or an advanced seismic event bulletin produced by the International Data Centre (IDC) of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO PrepCom) could reduce uncertainties and improve confidence in analyses. Specifically, temporally-separated images can reduce uncertainty by identifying areas where change has occurred (e.g., building construction or demolition, road or facilities improvements). The primary goal of this project was to develop an automated geospatial processing script for imagery change detection to better reflect needs of the technical community (including the IDC) and to make the use of such a tool accessible in a variety of settings across platforms. Technical experts at Los Alamos National Laboratory successfully built GAIA: the Geospatial Automated Imagery Analysis tool, to fill this need. GAIA combines five tool components to produce orthorectified time separated imagery and imagery change detection maps. Our toolkit (1) reduces error by providing a standardized workflow for image analyses and (2) significantly reduces processing time from between 7 and 24+ hours to approximately 5 minutes. Technical experts at Sandia National Laboratories supported GAIA via beta-testing and by introducing a web-based system approach for increased applicability. To test the function, performance, broad application, and ease-of-use of GAIA, we applied it to four separate test cases. The results of this preliminary investigation show promise in reducing uncertainty in seismic event locations: if satellite imagery can show regions where operations that produce seismic activity likely occurred, then pursuing imagery to locate epicenters of seismic nuclear events could reduce the time needed to find the true epicenter location.

58 GEOSCIENCES↗

Imagery Applications for Advanced Event Analytics (WBS 24.3.1.3.3-IDC FY2020 Final Project Report)

Accurate event locations and replicability of location analyses are essential for assessing the nature of an event, its context, ambient site conditions, and proximity to relevant facilities and infrastructure. Additionally, accurate event locations provide valuable information that reduce uncertainties, improve confidence in event analyses, and inform in-field verification activities. However, event location/relocation and replicability are difficult due to a number of factors, including spatially-sparse network coverage in some areas of the globe and variability in seismic data processing. This team proposed that the incorporation of high-fidelity imagery as a data backbone to the analytical assessment of a suspected underground explosion and/or an advanced seismic event bulletin produced by the International Data Centre (IDC) of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO PrepCom) could reduce uncertainties and improve confidence in analyses. Specifically, temporally-separated images can reduce uncertainty by identifying areas where change has occurred (e.g., building construction or demolition, road or facilities improvements). The primary goal of this project was to develop an automated geospatial processing script for imagery change detection to better reflect needs of the technical community (including the IDC) and to make the use of such a tool accessible in a variety of settings across platforms. Technical experts at Los Alamos National Laboratory successfully built GAIA: the Geospatial Automated Imagery Analysis tool, to fill this need. GAIA combines five tool components to produce orthorectified time-separated imagery and imagery change detection maps. Our toolkit (1) reduces error by providing a standardized workflow for image analyses and (2) significantly reduces processing time from between 7 and 24+ hours to approximately 5 minutes. Technical experts at Sandia National Laboratories supported GAIA via beta-testing and by introducing a web-based system approach for increased applicability. To test the function, performance, broad application, and ease-of-use of GAIA, we applied it to four separate test cases. The results of this preliminary investigation show promise in reducing uncertainty in seismic event locations: if satellite imagery can show regions where operations that produce seismic activity likely occurred, then pursuing imagery to locate epicenters of seismic nuclear events could reduce the time needed to find the true epicenter location.

58 GEOSCIENCES↗

Monitoring the methanol conversion process in H-ZSM-5 using synchrotron X-ray powder diffraction-mass spectrometry

By monitoring the catalytic conversion of methanol using operando synchrotron powder X-ray diffraction (SXRD) and structure refinement, in combination with theoretical calculations, we demonstrate for the first time, that the concerted associative mechanism is responsible for dimethyl ether production via an activated protonated methanol intermediate species over H-ZSM-5 in an early stage of reaction at 200 °C. The minor contribution from the dissociative mechanism of the adsorbed methoxy intermediate species at Brønsted acid sites, renders their accumulation during the late stage of reaction, which leads to a build-up of the ‘hydrocarbon pool’ and eventually to ‘carbon’ through the formation of C-C bonds.

Lo, Benedict T W.↗

Networks and interfaces as catalysts for polymer materials innovation

Autonomous experimental systems offer a compelling glimpse into a future where closed-loop, iterative cycles—performed by machines and guided by artificial intelligence (AI) and machine learning (ML)—play a foundational role in materials research and development. This perspective draws attention to the roles of networks and interfaces—of and between humans and machines—for the purpose of generating knowledge and accelerating innovation. Polymers, a class of materials with massive global impact, present a unique opportunity for the application of informatics and automation to pressing societal challenges. To develop these networks and interfaces in polymer science, the Community Resource for Innovation in Polymer Technology (CRIPT)—a polymer data ecosystem based on novel polymer data model, representation, search, and visualization technologies—is introduced. The ongoing co-design efforts engage stakeholders in industry, academia, and government to uncover rapidly actionable, high-impact opportunities to build networks, bridge interfaces, and catalyze innovation in polymer technology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Smallest fullerene-like silicon cage stabilized by a V{sub 2} unit

We conducted a combined anion photoelectron spectroscopy and density functional theory study on V{sub 2}Si{sub 20} cluster. Our results show that the V{sub 2}Si{sub 20} cluster has an elongated dodecahedron cage structure with a V{sub 2} unit encapsulated inside the cage. It is the smallest fullerene-like silicon cage and can be used as building block to make cluster-assembled materials, such as pearl-chain style nanowires.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗