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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Eu(Mg4Al3)4 by Materials Project

Eu(Mg4Al3)4 crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to three equivalent Mg, one Eu, and six equivalent Al atoms. All Mg–Mg bond lengths are 3.05 Å. The Mg–Eu bond length is 3.29 Å. All Mg–Al bond lengths are 3.18 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five equivalent Al atoms. There are two shorter (3.11 Å) and four longer (3.19 Å) Mg–Mg bond lengths. There are a spread of Mg–Al bond distances ranging from 2.88–3.18 Å. Eu is bonded in a 12-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Eu–Al bond lengths are 3.24 Å. Al is bonded in a 11-coordinate geometry to seven Mg, one Eu, and three equivalent Al atoms. There are one shorter (2.70 Å) and two longer (2.82 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(In2Ag)4 by Materials Project

EuAg4In8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to eight equivalent Ag and twelve In atoms. All Eu–Ag bond lengths are 4.07 Å. There are four shorter (3.69 Å) and eight longer (3.84 Å) Eu–In bond lengths. Ag is bonded in a 12-coordinate geometry to two equivalent Eu, two equivalent Ag, and eight In atoms. Both Ag–Ag bond lengths are 3.11 Å. There are four shorter (3.11 Å) and four longer (3.25 Å) Ag–In bond lengths. There are two inequivalent In sites. In the first In site, In is bonded in a 10-coordinate geometry to one Eu, four equivalent Ag, and five In atoms. There are a spread of In–In bond distances ranging from 3.25–3.47 Å. In the second In site, In is bonded in a 12-coordinate geometry to two equivalent Eu, four equivalent Ag, and six In atoms. Both In–In bond lengths are 3.19 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Elucidating the Structure of the Eu‐EDTA Complex in Solution at Various Protonation States

Abstract Ethylenediaminetetraacetic acid (EDTA), which has two amine and four carboxylate protonation sites, forms stable complexes with lanthanide ions. This work analyzes the coordination structure, in atomic resolution, of the Eu 3+ ion complexed with EDTA in all its protonation states in aqueous solution. Eu‐EDTA complexes were modeled using classical molecular dynamics (MD) simulations using force field parameters optimized with ab initio molecular dynamics (AIMD) simulations. Structures from the MD simulations were used to predict extended X‐ray absorption fine structure (EXAFS) spectra and compared with EXAFS measurements of the Eu 3+ aqua ion and Eu‐EDTA complexes at pH 3 and 11. This work details how Eu‐EDTA complex coordination structures change with increasing protonation of the EDTA ligand in the complex, from the tightly bound unprotonated complex to the unbinding of the fully protonated EDTA ligand from the Eu 3+ ion as both become solvated by water. Agreement between predicted and measured EXAFS spectra supports the findings from simulation.

Chemistry↗
DOE OSTI2023

Combustion synthesis of Eu 2 O 3 nanomaterials with tunable phase composition and morphology

Combustion reactions in europium nitrate – acetylacetone – 2-methoxyethanol solutions and gels were investigated to produce europium (III) oxide (Eu 2 O 3 ) nanocrystalline materials and thin films. Thermal analyses of solutions indicated that the 2-methoxyethanol solvent also acts as a fuel in the absence of acetylacetone. Adding acetylacetone increases the overall heat of the reaction. Thermal analysis results revealed that the slow oxidation of unburned hydrocarbon residues follows the primary combustion reaction. Time-temperature profile measurements of the bulk combustion synthesis process in air and nitrogen atmospheres enabled the extraction of the maximum reaction temperature and the heating and cooling rates in the combustion zone. Several direct correlations exist between measured combustion parameters and the phase composition of the products. Combustion in air results in mixed-phase cubic and monoclinic nanocrystalline Eu 2 O 3 . Increasing the acetylacetone concentration in solutions increases the synthesis temperature and decreases the quantity of cubic Eu 2 O 3 . Here, the reaction of solutions in a nitrogen atmosphere or diluted with Eu 2 O 3 provides control of the product phase composition and reduces the quantity of the monoclinic phase. Transmission electron microscopy imaging shows that the Eu 2 O 3 end products are highly porous aggregates of nanocrystalline particles. Electrospraying of reactive solutions onto different substrates followed by short annealing makes the preparation of Eu 2 O 3 materials with diverse morphologies possible.

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

TlSr 2 I 5 :Eu 2+ - A new high density scintillator for gamma-ray detection

In this paper we report on the scintillation properties of TlSr 2 I 5 doped with Eu 2+ , a novel thallium-containing high-resolution scintillator for gamma-ray spectroscopy. Here, small diameter, good quality crystals of TlSr 2 I 5 :Eu (TSI) with different Eu 2+ concentrations were grown by the vertical Bridgman method. X-ray diffraction measurements show that single crystals of TSI belong to the monoclinic system with space group P2 1 /c. TlSr 2 I 5 has a density of 5.32 g/cm 3 and effective Z of 60. The X-ray excited emission of Eu 2+ doped TlSr 2 I 5 features a broad emission band peaking between 460–470 nm. The light yield of TlSr 2 I 5 crystal doped with 1% Eu 2+ is measured to be ~72,000 ph/MeV with an energy resolution of 2.8% at 662 keV. The scintillation decay time which is characteristic of Eu 2+ shows two components, with 90% of the light in a ~500 ns component and the rest in a longer component of ~3 μs.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Continuous Evolution of Eu 2+ /Eu 3+ Mixed Valency Driven by Pressure and Temperature

Continuous mixed valency involving Eu 2+ and Eu 3+ in Eu 4 Bi 6 Se 13 can be induced under applied pressure or at reduced temperatures. The monoclinic structure of Eu 4 Bi 6 Se 13 , crystallizing in the P2 1 /m space group (No. 11), features linear chains of Eu atoms aligned along the b-axis. Magnetic susceptibility measurements, conducted both parallel and perpendicular to the b-axis and analyzed using Curie–Weiss theory, alongside high-pressure partial fluorescence yield (PFY) data from X-ray absorption spectroscopy (XAS), indicate the material’s propensity to adopt a mixed-valent state. Within this state, the trivalent Eu 3+ configuration becomes increasingly favored as the pressure rises or the temperature decreases.

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

Magnetic phase transitions in Eu(Co 1-x Nix) 2-y As 2 single crystals

The effects of Ni doping in Eu(Co 1-x Ni x ) 2-y As 2 single crystals with x = 0 to 1 grown out of self flux are investigated via crystallographic, electronic transport, magnetic, and thermal measurements. All compositions adopt the body-centered-tetragonal ThCr 2 Si 2 structure with space group I 4= mmm . Here, we also find 3-4% of randomly-distributed vacancies on the Co/Ni site. Anisotropic magnetic susceptibility $\chi$α (α = ab; c) data versus temperature T show clear signatures of an antiferromagnetic (AFM) c-axis helix structure associated with the Eu +2 spins-7/2 for x = 0 and x = 1 as previously reported. The $\chi$α (T) data for x = 0.03 and 0.10 suggest an anomalous 2 q magnetic structure containing two helix axes along the c axis and in the ab plane, respectively, whereas for x = 0.75, 0.82, and 1 a c-axis helix is inferred as previously found for x = 1. At intermediate compositions x = 0:2, 0.32, 0.42, 0.54, and 0.65 a magnetic structure with a large ferromagnetic (FM) c-axis component is found from magnetization versus fi eld isotherms, suggested to be an incommensurate FM cone structure associated with the Eu spins, which consists of both AFM and FM components. In addition, the $\chi$ (T) and heat capacity C p (T) data for x = 0.2-0.65 indicate the occurrence of itinerant FM order associated with the Co/Ni atoms with Curie temperatures from 60 K to 25 K, respectively. Electrical resistivity ρ(T) measurements indicate metallic character for all compositions with abrupt increases in slope on cooling below the Eu AFM transition temperatures. In addition to this panoply of magnetic transitions, 151 Eu Mössbauer measurements indicate that ordering of the Eu moments proceeds via an incommensurate sine amplitude-modulated structure with additional transition temperatures associated with this effect.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Eu(III) and Cm(III) Complexation by the Aminocarboxylates NTA, EDTA, and EGTA Studied with NMR, TRLFS, and ITC—An Improved Approach to More Robust Thermodynamics

The complex formation of Eu(III) and Cm(III) was studied via tetradentate, hexadentate, and octadentate coordinating ligands of the aminopolycarboxylate family, viz., nitrilotriacetate (NTA 3- ), ethylenediaminetetraacetate (EDTA 4- ), and ethylene glycol-bis(2-aminoethyl ether)-N,N,N',N'-tetraacetate (EGTA 4- ), respectively. Based on the complexones’ pK a values obtained from 1 H nuclear magnetic resonance (NMR) spectroscopic pH titration, complex formation constants were determined by means of the parallel-factor-analysis-assisted evaluation of Eu(III) and Cm(III) time-resolved laser-induced fluorescence spectroscopy (TRLFS). This was complemented by isothermal titration calorimetry (ITC), providing the enthalpy and entropy of the complex formation. This allowed us to obtain genuine species along with their molecular structures and corresponding reliable thermodynamic data. The three investigated complexones formed 1:1 complexes with both Eu(III) and Cm(III). Besides the established Eu(III)–NTA 1:1 and 1:2 complexes, we observed, for the first time, the existence of a Eu(III)–NTA 2:2 complex of millimolar metal and ligand concentrations. Demonstrated for thermodynamic studies on Eu(III) and Cm(III) interaction with complexones, the utilized approach is commonly applicable to many other metal–ligand systems, even to high-affinity ligands.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2019

Exposure of the EU-28 Food Imports to Extreme Weather Disasters in Exporting Countries

EU-28 relies on a diversified foreign market, even for crops for which it has a high self-sufficiency.This study contributes to the discussion on the vulnerability of agri-food supply to the impacts of extreme weather disasters (EWD). We focus on the largest import commodities of the EU-28 and we aim to (1) map external dependencies of EU-28 agri-food sector, (2) estimate the impact of EWD on crop production in countries from which the EU-28 receives their imports, and (3) assess the exposure of EU-28 agri-food imports to such impacts. Crop and trade data areacquired through EUROSTAT and FAOSTAT, EWD records from EM-DAT, all between 1961 and 2016. A superposed epoch analysis is used to estimate the impact of EWD on the average national production, yield and harvested area of selected crops in exporting countries. The EU-28 imports between 35-100% of its consumption of soybeans, banana, tropical fruits, coffee and cocoa. Our study reveals a substantial impact of EWD, especially due to droughts andheat waves, on the production of soybeans, tropical fruits, and cocoa, with import weighted impacts of 3, 8, and 7%, respectively. Floods cause weighted impacts of 7% (soybeans) and 8% (tropical fruits). Coffee production shows gains during cold waves, but the inter-annual variability offsets these effects.

Teresa Armada Bras↗
DOE OSTI2020

Materials Data on Eu(ZnGe)2 by Materials Project

EuZn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Zn and eight equivalent Ge atoms. All Eu–Zn bond lengths are 3.45 Å. All Eu–Ge bond lengths are 3.32 Å. Zn is bonded to four equivalent Eu and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing ZnEu4Ge4 tetrahedra. All Zn–Ge bond lengths are 2.59 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Zn, and one Ge atom. The Ge–Ge bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(AlGa)2 by Materials Project

EuAl2Ga2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Ga and eight equivalent Al atoms. All Eu–Ga bond lengths are 3.31 Å. All Eu–Al bond lengths are 3.50 Å. Ga is bonded in a 9-coordinate geometry to four equivalent Eu, one Ga, and four equivalent Al atoms. The Ga–Ga bond length is 2.51 Å. All Ga–Al bond lengths are 2.63 Å. Al is bonded to four equivalent Eu and four equivalent Ga atoms to form a mixture of distorted corner, edge, and face-sharing AlEu4Ga4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(ZnSi)2 by Materials Project

EuZn2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Zn and eight equivalent Si atoms. All Eu–Zn bond lengths are 3.33 Å. All Eu–Si bond lengths are 3.24 Å. Zn is bonded to four equivalent Eu and four equivalent Si atoms to form a mixture of distorted edge, face, and corner-sharing ZnEu4Si4 tetrahedra. All Zn–Si bond lengths are 2.54 Å. Si is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Zn, and one Si atom. The Si–Si bond length is 2.37 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(NiGe)2 by Materials Project

EuNi2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Eu–Ni bond lengths are 3.26 Å. All Eu–Ge bond lengths are 3.22 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.38 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(CuGe)2 by Materials Project

EuCu2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Eu–Cu bond lengths are 3.32 Å. All Eu–Ge bond lengths are 3.23 Å. Cu is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Ge atoms. All Cu–Ge bond lengths are 2.47 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(MgGe)3 by Materials Project

Eu(MgGe)3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent Mg sites. In the first Mg site, Mg is bonded to four Ge atoms to form a mixture of corner and edge-sharing MgGe4 tetrahedra. There are two shorter (2.73 Å) and two longer (2.80 Å) Mg–Ge bond lengths. In the second Mg site, Mg is bonded to four Ge atoms to form a mixture of corner and edge-sharing MgGe4 tetrahedra. There are two shorter (2.76 Å) and two longer (2.78 Å) Mg–Ge bond lengths. In the third Mg site, Mg is bonded to four equivalent Ge atoms to form a mixture of corner and edge-sharing MgGe4 tetrahedra. There are two shorter (2.74 Å) and two longer (2.80 Å) Mg–Ge bond lengths. Eu is bonded in a 2-coordinate geometry to ten Ge atoms. There are a spread of Eu–Ge bond distances ranging from 3.17–3.46 Å. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six equivalent Eu and three Ge atoms. There are one shorter (2.50 Å) and two longer (2.52 Å) Ge–Ge bond lengths. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four Mg, four equivalent Eu, and one Ge atom. In the third Ge site, Ge is bonded in a body-centered cubic geometry to eight Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(ClO4)3 by Materials Project

Eu(ClO4)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Eu is bonded in a 9-coordinate geometry to nine O atoms. There are six shorter (2.55 Å) and three longer (2.62 Å) Eu–O bond lengths. There are three inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.43 Å. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Eu and one Cl atom. The O–Cl bond length is 1.46 Å. In the third O site, O is bonded in a bent 150 degrees geometry to one Eu and one Cl atom. The O–Cl bond length is 1.47 Å. Cl is bonded in a tetrahedral geometry to four O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(MnGe)2 by Materials Project

EuMn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Mn and eight equivalent Ge atoms. All Eu–Mn bond lengths are 3.21 Å. All Eu–Ge bond lengths are 3.05 Å. Mn is bonded to four equivalent Eu and four equivalent Ge atoms to form a mixture of edge, face, and corner-sharing MnEu4Ge4 tetrahedra. All Mn–Ge bond lengths are 2.33 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(CuSn)2 by Materials Project

EuCu2Sn2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Eu is bonded in a 10-coordinate geometry to six equivalent Cu and four equivalent Sn atoms. There are two shorter (3.19 Å) and four longer (3.33 Å) Eu–Cu bond lengths. All Eu–Sn bond lengths are 3.47 Å. Cu is bonded in a 9-coordinate geometry to three equivalent Eu, two equivalent Cu, and four equivalent Sn atoms. Both Cu–Cu bond lengths are 2.60 Å. There are a spread of Cu–Sn bond distances ranging from 2.61–2.68 Å. Sn is bonded in a 9-coordinate geometry to two equivalent Eu, four equivalent Cu, and one Sn atom. The Sn–Sn bond length is 3.05 Å.

36 MATERIALS SCIENCE↗