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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Synthesis, Crystal Structure, and Optical Properties of the Barium meta -Pertechnetate Ba[TcO 4 ] 2

High-quality single crystals of the colorless title compound Ba[ 99 TcO 4 ] 2 were prepared from radioactive, isotope-pure 99 TcO 2 by oxidation with H 2 O 2 in an aqueous ammonia solution and subsequent cation metathesis using an ion-exchange column. Single-crystal X-ray diffraction revealed Ba[TcO 4 ] 2 to crystallize isotopically to Ba[MnO 4 ] 2 in the orthorhombic space group Fddd with the lattice parameters a = 747.34(5) pm, b = 1244.08(7) pm, and c = 1511.23(9) pm for Z = 8. Its crystal structure features [BaO 12 ] 22- icosahedra surrounded by ten [TcO 4 ] - tetrahedra connected via two edges and eight corners. The optical properties of Ba[TcO 4 ] 2 investigated by UV-vis spectroscopy show the broad O 2- → Tc 7+ ligand-to-metal charge transfer (2p → 4d) process within these discrete [TcO 4 ]- anions at an absorption maximum of around 350 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

The crystal structure of methanogen McrD , a methyl‐coenzyme M reductase‐associated protein

Methyl‐coenzyme M reductase (MCR) is a multi‐subunit (α 2 β 2 γ 2 ) enzyme responsible for methane formation via its unique F 430 cofactor. The genes responsible for producing MCR ( mcrA , mcrB and mcrG ) are typically colocated with two other highly conserved genes mcrC and mcrD . We present here the high‐resolution crystal structure for McrD from a human gut methanogen Methanomassiliicoccus luminyensis strain B10. The structure reveals that McrD comprises a ferredoxin‐like domain assembled into an α + β barrel‐like dimer with conformational flexibility exhibited by a functional loop. The description of the M. luminyensis McrD crystal structure contributes to our understanding of this key conserved methanogen protein typically responsible for promoting MCR activity and the production of methane, a greenhouse gas.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Relationship among the Crystal Structure, Texture, and Macroscopic Properties of Tetragonal (Pb,La)(Zr,Ti)O 3 Ferroelectrics Investigated by In Situ High-Energy Synchrotron Diffraction

In situ diffraction investigations have played an important role in experimentally revealing the mechanism of piezoelectric and ferroelectric properties. In this study, a pure tetragonal ferroelectric ceramic of La-doped PbZr 0.5 Ti 0.5 O 3 (LaPZT50) was investigated to eliminate the complex influence of phase coexistence. The electric field evolutions of the crystal structure, domain switching, and lattice deformation of the tetragonal phase have been revealed by in situ high-energy synchrotron X-ray diffraction. Furthermore, we found that the crystal structure of LaPZT50 is quite stable, showing a negligible change in the Pb–O bond length, unit cell volume, and spontaneous polarization upon application of an in situ external electric field. Importantly, the maximum macroscopic polarization of tetragonal LaPZT50 is defined by the 111-oriented grains. As determined by the intensity difference, the switching of non-180° domains plays a more significant role in contributing to the macroscopic strain than lattice deformation. These results further imply that the phase coexistence around the morphotropic phase boundary facilitates domain wall motion in the tetragonal phase and improves the ferroelectric and piezoelectric properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Crystal structures and comparisons of huntite aluminum borates RE Al 3 (BO 3 ) 4 ( RE = Tb, Dy and Ho)

Three huntite-type aluminoborates of stoichiometry RE Al 3 (BO 3 ) 4 ( RE = Tb, Dy and Ho), namely, terbium/dysprosium/holmium trialuminium tetrakis(borate), were synthesized by slow cooling within a K 2 Mo 3 O 10 flux with spontaneous crystallization. The crystal structures were determined using single-crystal X-ray diffraction (SC-XRD) data. The synthesized borates are isostructural to the huntite [CaMg 3 (CO 3 ) 4 ] structure and crystallized within the trigonal R 32 space group. The structural parameters were compared to literature data of other huntite RE Al 3 (BO 3 ) 4 crystals within the R 32 space group. All three borates fit well into the trends calculated from the literature data. The unit-cell parameters and volumes increase linearly with larger RE cations whereas the densities decrease. All of the crystals studied were refined as inversion twins.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Crystal structure of imepitoin, C 13 H 14 ClN 3 O 2

The crystal structure of imepitoin has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Imepitoin crystallizes in space group Pbca (#61) with a = 12.35541(2), b = 28.43308(8), c = 7.340917(7) Å, V = 2578.882(7) Å 3 , and Z = 8. The roughly planar molecules stack along the c-axis. There are no traditional hydrogen bonds in the structure, but several intramolecular and intermolecular C–H∙∙∙O, C–H∙∙∙N, and C–H∙∙∙Cl hydrogen bonds contribute to the crystal energy. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mycobacterial DNA polymerase I: activities and crystal structures of the POL domain as apoenzyme and in complex with a DNA primer-template and of the full-length FEN/EXO–POL enzyme

Mycobacterial Pol1 is a bifunctional enzyme composed of an N-terminal DNA flap endonuclease/5' exonuclease domain (FEN/EXO) and a C-terminal DNA polymerase domain (POL). Here we document additional functions of Pol1: FEN activity on the flap RNA strand of an RNA:DNA hybrid and reverse transcriptase activity on a DNA-primed RNA template. We report crystal structures of the POL domain, as apoenzyme and as ternary complex with 3'-dideoxy-terminated DNA primer-template and dNTP. The thumb, palm, and fingers subdomains of POL form an extensive interface with the primer-template and the triphosphate of the incoming dNTP. Progression from an open conformation of the apoenzyme to a nearly closed conformation of the ternary complex entails a disordered-to-ordered transition of several segments of the thumb and fingers modules and an inward motion of the fingers subdomain—especially the O helix—to engage the primer-template and dNTP triphosphate. Distinctive structural features of mycobacterial Pol1 POL include a manganese binding site in the vestigial 3' exonuclease subdomain and a non-catalytic water-bridged magnesium complex at the protein-DNA interface. We report a crystal structure of the bifunctional FEN/EXO–POL apoenzyme that reveals the positions of two active site metals in the FEN/EXO domain.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

The crystal structure of Grindelia robusta 7,13-copalyl diphosphate synthase reveals active site features controlling catalytic specificity

Diterpenoid natural products serve critical functions in plant development and ecological adaptation and many diterpenoids have economic value as bioproducts. The family of class II diterpene synthases catalyzes the committed reactions in diterpenoid biosynthesis, converting a common geranylgeranyl diphosphate precursor into different bicyclic prenyl diphosphate scaffolds. Enzymatic rearrangement and modification of these precursors generate the diversity of bioactive diterpenoids. We report the crystal structure of Grindelia robusta 7,13-copalyl diphosphate synthase, GrTPS2, at 2.1 Å of resolution. GrTPS2 catalyzes the committed reaction in the biosynthesis of grindelic acid, which represents the signature metabolite in species of gumweed (Grindelia spp., Asteraceae). Grindelic acid has been explored as a potential source for drug leads and biofuel production. The GrTPS2 crystal structure adopts the conserved three-domain fold of class II diterpene synthases featuring a functional active site in the γβ-domain and a vestigial α-domain. Substrate docking into the active site of the GrTPS2 apo protein structure predicted catalytic amino acids. Biochemical characterization of protein variants identified residues with impact on enzyme activity and catalytic specificity. Specifically, mutagenesis of Y457 provided mechanistic insight into the position-specific deprotonation of the intermediary carbocation to form the characteristic 7,13 double bond of 7,13-copalyl diphosphate.

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

Crystal structure of oxibendazole, C 12 H 15 N 3 O 3

The crystal structure of oxibendazole has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Oxibendazole crystallizes in space group C2/c (#15) with a = 23.18673(22), b = 5.35136(5), c = 19.88932(13) Å, β = 97.0876(9)°, V = 2449.018(17) Å 3 , and Z = 8. The structure consists of hydrogen-bonded layers of planar molecules parallel to the bc-plane. Strong N–H∙∙∙N hydrogen bonds link the molecules into dimers, with a graph set R2,2(8). N–H∙∙∙O hydrogen bonds further link these dimers into layers parallel to the bc-plane. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

36 MATERIALS SCIENCE↗
DOE OSTI2022

Crystal structure of haloxon, C 14 H 14 C l3 O 6 P

The crystal structure of haloxon has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Haloxon crystallizes in space group P2 1 /n (#14) with a = 19.60382(6), b = 10.05473(3), c = 8.73591(2) Å, β = 92.6617(2)°, V = 1720.088(11) Å 3 , and Z = 4. The structure consists of discrete molecules. The mean planes of the fused ring systems are approximately 0–11 and 011. The rings form staggered stacks perpendicular to these planes. There are no traditional hydrogen bonds in the structure, but several C–H∙∙∙O and C–H∙∙∙Cl hydrogen bonds contribute to the crystal energy. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

36 MATERIALS SCIENCE↗
DOE OSTI2022

Exploring the use of the pentaphenylcyclopentadienyl ligand in uranium chemistry: the crystal structure of (C

The reaction of UI3 with NaC5Ph5 in THF generated (η5-C5Ph5)UI2(THF)2 which was characterized by X-ray crystallography. The complex has a four-legged piano stool structure with a 2.539 Å U– (C5Ph5 ring centroid) distance that is slightly longer than the 2.504 Å distance in (η5-C5Me5)UI2(THF)3 which has a larger formal coordination number. Although the synthesis of the mono-cyclopentadienyl complex was facile, no bis-cyclopentadienyl complexes were isolated from reactions using two equivalents of the pentaphenylcyclopentadienyl ligand per uranium. In one UI3/2NaC5Ph5 synthesis, the X-ray crystal structure of (THF)3Na(η5-C5Ph5) was obtained. Attempts to reduce (η5-C5Ph5)UI2(THF)2 did not give evidence for a UII product. KC8 reductions of the in situ reaction of NdI3 and NaC5Ph5, analogous to the synthesis of (η5-C5Ph5)UI2(THF)2, yielded an X-ray crystal structure of a solvent-separated ion pair (SSIP), [K(18-crown-6)(THF)2][C5Ph5].

Chemistry↗
DOE OSTI2025

Crystal structure of Cu2Zn(GexSi1−x)Se4 solid solution: the kesterite to wurtz–kesterite structural phase transition

Developing low-cost, sustainable, and environmentally friendly top absorber layers for tandem solar cells is essential to advancing photovoltaic technologies and accelerating the transition to renewable energy. In this work, we explore the potential of tetravalent (Cu2Zn(GexSi1−x)Se4) cation mutations in chalcogenide compound semiconductors with the aim of finding a material with increased band gap and reduced structural disorder. A combination of high-resolution synchrotron powder diffraction and neutron powder diffraction was used to determine the atomic positions and monoclinic angles in monoclinic wurtz–kesterite type Cu2Zn(GexSi1−x)Se4 mixed crystals as well as to determine the cation distribution in the crystal structure of Ge-rich kesterite-type and Si-rich wurtz–kesterite type mixed crystals. These investigations enabled us to deduce the structural transition scenario within the Cu2Zn(GexSi1−x)Se4 series. The transition occurs via a region where two phases with different crystal structures, tetragonal and monoclinic and thus a different distortion of the coordination tetrahedra, but the same cation distribution within the element specific cation sites co-exist. Thus, the structural transition between the kesterite and the wurtz–kesterite structure within the Cu2Zn(GexSi1−x)Se4 series is a distortion driven transition. The study identifies cation mutation in quaternary chalcogenides as a promising strategy beyond chalcopyrites and kesterites for low cost and environmentally friendly top absorbers in tandem solar cells.

Gurieva, Galina [Helmholtz Center Berlin for Mater↗
DOE OSTI2024

The crystal structure of bacteriophage λ RexA provides novel insights into the DNA binding properties of Rex-like phage exclusion proteins

Abstract RexA and RexB function as an exclusion system that prevents bacteriophage T4rII mutants from growing on Escherichia coli λ phage lysogens. Recent data established that RexA is a non-specific DNA binding protein that can act independently of RexB to bias the λ bistable switch toward the lytic state, preventing conversion back to lysogeny. The molecular interactions underlying these activities are unknown, owing in part to a dearth of structural information. Here, we present the 2.05-Å crystal structure of the λ RexA dimer, which reveals a two-domain architecture with unexpected structural homology to the recombination-associated protein RdgC. Modelling suggests that our structure adopts a closed conformation and would require significant domain rearrangements to facilitate DNA binding. Mutagenesis coupled with electromobility shift assays, limited proteolysis, and double electron–electron spin resonance spectroscopy support a DNA-dependent conformational change. In vivo phenotypes of RexA mutants suggest that DNA binding is not a strict requirement for phage exclusion but may directly contribute to modulation of the bistable switch. We further demonstrate that RexA homologs from other temperate phages also dimerize and bind DNA in vitro. Collectively, these findings advance our mechanistic understanding of Rex functions and provide new evolutionary insights into different aspects of phage biology.

Biochemistry & Molecular Biology↗
DOE OSTI2021

Crystal Structure and Preparation of Li7La3Zr2O12 (LLZO) Solid-State Electrolyte and Doping Impacts on the Conductivity: An Overview

As an essential part of solid-state lithium-ion batteries, solid electrolytes are receiving increasing interest. Among all solid electrolytes, garnet-type Li7La3Zr2O12 (LLZO) has proven to be one of the most promising electrolytes because of its high ionic conductivity at room temperature, low activation energy, good chemical and electrochemical stability, and wide potential window. Since the first report of LLZO, extensive research has been done in both experimental investigations and theoretical simulations aiming to improve its performance and make LLZO a feasible solid electrolyte. These include developing different methods for the synthesis of LLZO, using different crucibles and different sintering temperatures to stabilize the crystal structure, and adopting different methods of cation doping to achieve more stable LLZO with a higher ionic conductivity and lower activation energy. It also includes intensive efforts made to reveal the mechanism of Li ion movement and understand its determination of the ionic conductivity of the material through molecular dynamic simulations. Nonetheless, more insightful study is expected in order to obtain LLZO with a higher ionic conductivity at room temperature and further improve chemical and electrochemical stability, while optimal multiple doping is thought to be a feasible and promising route. This review summarizes recent progress in the investigations of crystal structure and preparation of LLZO, and the impacts of doping on the lithium ionic conductivity of LLZO.

Raju, Md Mozammal (ORCID:0000000319040523)↗
DOE OSTI2021

Explorations of the nonheme high-valent iron-oxo landscape: crystal structure of a synthetic complex with an [Fe IV 2 (μ-O) 2 ] diamond core relevant to the chemistry of sMMOH

Methanotrophic bacteria utilize methane monooxygenase (MMO) to carry out the first step in metabolizing methane. The soluble enzymes employ a hydroxylase component (sMMOH) with a nonheme diiron active site that activates O 2 and generates a powerful oxidant capable of converting methane to methanol. It is proposed that the diiron(II) center in the reduced enzyme reacts with O 2 to generate a diferric-peroxo intermediate called P that then undergoes O–O cleavage to convert into a diiron(IV) derivative called Q, which carries out methane hydroxylation. Most (but not all) of the spectroscopic data of Q accumulated by various groups to date favor the presence of an Fe IV 2 (μ-O) 2 unit with a diamond core. The Que lab has had a long-term interest in making synthetic analogs of iron enzyme intermediates. To this end, the first crystal structure of a complex with a Fe III Fe IV (μ-O) 2 diamond core was reported in 1999, which exhibited an Fe∙∙∙Fe distance of 2.683(1) Å. Now more than 20 years later, a complex with an Fe IV 2 (μ-O) 2 diamond core has been synthesized in sufficient purity to allow diffraction-quality crystals to be grown. Finally, its crystal structure has been solved, revealing an Fe∙∙∙Fe distance of 2.711(4) Å for comparison with structural data for related complexes with lower iron oxidation states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗