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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

β decay of Ba 141

The β-decay strength function of nuclides produced in fission is important as it dictates the distribution of decay energy between electrons, neutrinos, and γ rays and so is critical for calculating decay heat in reactors and for estimating the reactor antineutrino spectrum. Several experimental techniques are available to determine this strength function, including electron spectroscopy, γ-ray calorimetry (TAGS spectroscopy), and detailed, high-resolution spectroscopy with modern large high-purity germanium arrays. This work investigates the decay of the well-known and strongly produced fission fragment 141 Ba. A beam of 141 Cs was implanted at the target position of the Gammasphere and the subsequent decay of the daughter 141 Ba was studied. Extensive decay spectroscopy was possible up to the decay Q value of 3.197(7) MeV, including a significant extension of the level scheme and detailed angular correlation measurements for all levels with greater than 0.25% β feeding. The distribution of the β-decay strength was then inferred and compared to previous calorimetric studies. In conclusion, the agreement was excellent and provides a benchmark for comparing strength function methods and data for a more detailed understanding of the structure of 141 La.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Coexistence of Reflection Asymmetric and Symmetric Shapes in $^{144}\mathrm{Ba}$

Level structures in the neutron-rich $^{144}\mathrm{Ba}$ nucleus have been reinvestigated by measuring prompt gamma rays in the spontaneous fission of $^{252}\mathrm{Cf}$. The previous $s = +1$ octupole band structure with reflection asymmetric shape has been expanded, and a side quadrupole band structure based on a $3^+$ state with reflection symmetric shape is identified. Thus, the results show the coexistence of reflection asymmetric and symmetric shapes in $^{144}\mathrm{Ba}$. This is a first identification of such a shape coexistence structure in a nuclear structure. Finally, the other structural characteristics are discussed.

144Ba↗
DOE OSTI2025

Doping Dependence of 2-Spinon Excitations in the Doped 1D Cuprate Ba 2 ⁢CuO 3+δ

Recent photoemission experiments on the quasi-one-dimensional Ba-based cuprates suggest that doped holes experience an attractive potential not captured using the simple Hubbard model. This observation has garnered significant attention due to its potential relevance to Cooper pair formation in high-T c cuprate superconductors. To scrutinize this assertion, we examined signatures of such an attractive potential in doped 1D cuprates Ba 2 ⁢CuO 3+δ by measuring the dispersion of the 2-spinon excitations using Cu L 3 -edge resonant inelastic x-ray scattering (RIXS). Upon doping, the 2-spinon excitations appear to weaken, with a shift of the minimal position corresponding to the nesting vector of the Fermi points, q F . Notably, we find that the energy scale of the 2-spinons near the Brillouin zone boundary is substantially softened compared to that predicted by the Hubbard model in one dimension. Finally, such a discrepancy implies missing ingredients, which lends support for the presence of an additional attractive potential between holes.

1-dimensional spin chains↗
DOE OSTI2023

Magnetic anisotropy and two-dimensional short-range chemical ordering in Ba 1−𝑥 ⁢Na 𝑥 ⁢Fe 2 ⁢As 2

A true understanding of the properties of pnictide superconductors requires the development of high-quality materials and performing measurements designed to unravel their intrinsic properties and short-range nematic correlations which are often obscured by extrinsic effects such as poor crystallinity, inhomogeneity, domain formation, and twinning. Here, in this paper, we report the systematic growth of high-quality Na-substituted BaFe 2 As 2 single crystals and their characterization using pulsed magnetic fields x-ray diffraction and x-ray diffuse scattering. Analysis of the properties and compositions of the highest-quality crystals shows that their actual Na stoichiometry is about 50-60% of the nominal content and that the targeted production of crystals with specific compositions is accessible. We derived a reliable equation to estimate the Na stoichiometry based on the measured superconducting T c of these materials. Attempting to force spin reorientation and induce tetragonality, orthorhombic Ba 1-x Na x Fe 2 As 2 single crystals subjected to out-of-plane magnetic fields up to 31.4T are found to exhibit strong in-plane magnetic anisotropy demonstrated by the insufficiency of such high fields in manipulating the relative population of their twinned domains or in suppressing the orthorhombic order. Broad x-ray diffuse-intensity rods observed at temperatures between 30 and 300 K uncover short-range structural correlations. Local structure modeling together with 3D-Δ pair-distribution function mapping of real-space interatomic vectors show that the diffuse scattering arises from in-plane short-range chemical correlations of the Ba and Na atoms coupled with short-range atomic displacements within the same plane due to an effective size difference between the two atomic species.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Potential Lifshitz transition at optimal substitution in nematic pnictide Ba 1 x Sr x Ni 2 As 2

BaNi 2 As 2 is a structural analog of the pnictide superconductor BaFe 2 As 2 , which, like the iron-based superconductors, hosts a variety of ordered phases including charge density waves (CDWs), electronic nematicity, and superconductivity. Upon isovalent Sr substitution on the Ba site, the charge and nematic orders are suppressed, followed by a sixfold enhancement of the superconducting transition temperature (T c ). To understand the mechanisms responsible for enhancement of T c , we present high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements of the Ba 1-x Sr x Ni 2 As 2 series, which agree well with our density functional theory (DFT) calculations throughout the substitution range. Analysis of our ARPES-validated DFT results indicates a Lifshitz transition and reasonably nested electron and hole Fermi pockets near optimal substitution where T c is maximum. These nested pockets host Ni d xz /d yz orbital compositions, which we associate with the enhancement of nematic fluctuations, revealing unexpected connections to the iron-pnictide superconductors. This gives credence to a scenario in which nematic fluctuations drive an enhanced T c .

36 MATERIALS SCIENCE↗
DOE OSTI2025

AmeriFlux FLUXNET-1F AR-Bal Balcarce BA

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site AR-Bal Balcarce BA. This is the FLUXNET version of the carbon flux data for the site AR-Bal Balcarce BA produced by applying the standard ONEFlux (1F) software. Site Description - The study was carried out in a 19-ha rainfed soybean plot at the Unidad Integrada Balcarce, located southeast of Buenos Aires, Argentina. The site is located in an environment of gentle hills at 130 m.a.s.l. Its soil was classified as a typical Argiudoll, with a loamy clayey texture up to 0.30 m and between 0.80 to 1.10 m depth, and a clayey texture between 0.30 and 0.80 m depth. The slope was 1:50 and oriented NE to SW. A caliche layer was found at 1 to 1.2 m depth thus the water table was considered beneath that level. The soybean variety used was DM 3810, Maturity Group III with an indeterminate growing habit. It was sown on November 21, 2012, and emerged on December 1. The crop archive had a maximum height of 0.75 m.

Gassmann, Maria Isabel [Universidad de Buenos Aire↗
DOE OSTI2024

An Analytical Tool to Evaluate Defect Thermodynamics of (La,Ba)Fe1-xMxO3-δ Perovskites for Solid-Oxide Cell Applications

A modeling tool of the defect thermodynamics of (La,Ba)Fe1-xMxO3-δ perovskites which includes energetic information about oxygen vacancy formation, hydration, hydride formation, and charge disproportionation reactions has been developed1. This tool incorporates defect energies and entropies expressed as sixth order polynomial functions to allow refinements of the defect reaction equilibrium constants in the thermodynamic analysis. Calculation of (La,Ba)Fe1-xMxO3-δ Brouwer diagrams as a function of pO2/pH2O and pH2/H2O in a range of temperatures of interest is facilitated by this modeling tool. The results obtained can provide direct guidance how the electronic and ionic defect concentrations of the triple conducting perovskite materials can be used to optimize performance of solid oxide cells for energy applications. The impact of magnetic and electronic structures of the perovskites on the defect reaction energies and entropies as obtained from density function theory modeling and the role played by hydride defect species will also be discussed.

Lee, Yueh-Lin↗
DOE OSTI2024

Migration of 60 Co, 133 Ba, 137 Cs, and 152 Eu from cementitious wasteforms in field lysimeter experiments

Safe and effective storage of radioactive waste is essential to protect environmental health. Due to the potential for accidental releases and the severity of the associated risks, it is imperative to further understand radionuclide transport should an accident occur. This work analyzed the vadose zone migration of radionuclides from cementitious wasteforms at the Savannah River Site after ten years. The observed radionuclides are prominent constituents of radioactive waste or analogs for other groups or series of radionuclides. Lysimeters were first analyzed in 2016 using a collimated high-purity germanium gamma-ray spectrometer to non-destructively measure the concentration of each radionuclide in the sediment column as a function of depth. Following these measurements, the lysimeters were redeployed in the field for another 4 years. All radionuclides in all lysimeters were observed to transport further during the redeployment period; however, the extent of migration varied with the material used for introduction. Except for 137 Cs, migration through the sediment control system increased with decreasing ionic potential (ionic charge/radius); migration order: 152 Eu< 137 Cs< 60 Co< 133 Ba. Overall, the cementitious wasteforms were observed to decrease radionuclide migration extent relative to the filter paper. In both cementitious wasteforms, the migration extent increased in the order 152 Eu< 133 Ba< 60 Co< 137 Cs. However, less migration was measured when the radionuclides were incorporated into a reducing grout wasteform. The novelty of this paper is the demonstration of a technique capable of creating non-destructive measurements over decade time scales. Ultimately, this work provides insight into the long-term migration of alkali, alkali earth, divalent transition metal, and trivalent actinide element isotopes.

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

Ba₁₋ₓSrₓFeO₃₋ᵧ as an Improved Oxygen Carrier for Chemical Looping Air Separation: A Computational and Experimental Study

Chemical looping air separation (CLAS) is a promising method to generate pure carbon-dioxide from fuel combustion with a pure oxygen stream, which is produced through the capture, and targeted release, of oxygen from the atmosphere using a solid oxide carrier. The performance of this process depends on the redox characteristics of the oxide carrier. Using experimental oxygen-temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA), the study shows that Ba₀․₇₅Sr₀․₂₅FeO₃ has improved oxygen storage capacity (OSC), oxidation, and reduction kinetics over pristine SrFeO₃ at temperatures ranging from 300-500 °C. The redox energetics computed by using first-principles density functional theory (DFT) calculations also depict the measured trend establishing it as an important descriptor of the measured performance. The Ba₁₋ₓSrₓFeO₃₋ᵧ depicts a Sr-substitution and oxygen stoichiometry induced structural phase transition from hexagonal at low temperatures to pseudo-cubic phase with higher OSC up to T=400 °C. Also, the mechanism leading to this structural phase transition is identified by performing electronic and vibrational structural calculations. This presentation was given on March 8, 2024 at the APS March Meeting in Minneapolis, MN.

Acharya, Shree Ram↗
DOE OSTI2020

Materials Data on Ba(CuSe)2 by Materials Project

BaCu2Se2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a body-centered cubic geometry to eight equivalent Se2- atoms. All Ba–Se bond lengths are 3.40 Å. Cu1+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.52 Å. Se2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AlSi)2 by Materials Project

BaAl2Si2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a body-centered cubic geometry to eight equivalent Si4- atoms. All Ba–Si bond lengths are 3.47 Å. Al3+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing AlSi4 tetrahedra. All Al–Si bond lengths are 2.56 Å. Si4- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ZnSb)2 by Materials Project

BaZn2Sb2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 7-coordinate geometry to seven Sb3- atoms. There are a spread of Ba–Sb bond distances ranging from 3.53–3.78 Å. There are two inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four Sb3- atoms to form a mixture of edge and corner-sharing ZnSb4 tetrahedra. There are a spread of Zn–Sb bond distances ranging from 2.71–2.80 Å. In the second Zn2+ site, Zn2+ is bonded to four Sb3- atoms to form a mixture of edge and corner-sharing ZnSb4 tetrahedra. There are a spread of Zn–Sb bond distances ranging from 2.69–2.85 Å. There are two inequivalent Sb3- sites. In the first Sb3- site, Sb3- is bonded in a 7-coordinate geometry to three equivalent Ba2+ and four Zn2+ atoms. In the second Sb3- site, Sb3- is bonded in a 4-coordinate geometry to four equivalent Ba2+ and four Zn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MnAs)2 by Materials Project

BaMn2As2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Ba–As bond lengths are 3.39 Å. Mn2+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing MnAs4 tetrahedra. All Mn–As bond lengths are 2.42 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ScTe2)2 by Materials Project

BaSc2Te4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.52–3.65 Å. There are two inequivalent Sc3+ sites. In the first Sc3+ site, Sc3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing ScTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Sc–Te bond distances ranging from 2.91–2.99 Å. In the second Sc3+ site, Sc3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing ScTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Sc–Te bond distances ranging from 2.93–3.03 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Sc3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sc3 trigonal bipyramids. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Sc3+ atoms. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Sc3+ atoms. In the fourth Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Sc3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sc3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(SmTe2)2 by Materials Project

BaSm2Te4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.58–3.79 Å. There are two inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing SmTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–62°. There are a spread of Sm–Te bond distances ranging from 3.11–3.19 Å. In the second Sm3+ site, Sm3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing SmTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–62°. There are a spread of Sm–Te bond distances ranging from 3.12–3.18 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Sm3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sm3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Sm3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sm3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Sm3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Sm3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(YTe2)2 by Materials Project

BaY2Te4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.57–3.76 Å. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing YTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Y–Te bond distances ranging from 3.07–3.13 Å. In the second Y3+ site, Y3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing YTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Y–Te bond distances ranging from 3.07–3.15 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Y3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Y3 trigonal bipyramids. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Y3+ atoms. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Y3+ atoms. In the fourth Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Y3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Y3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AgTe)2 by Materials Project

BaAg2Te2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 7-coordinate geometry to seven Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.50–3.78 Å. There are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 6-coordinate geometry to two equivalent Ag1+ and four Te2- atoms. Both Ag–Ag bond lengths are 2.94 Å. There are a spread of Ag–Te bond distances ranging from 2.87–2.95 Å. In the second Ag1+ site, Ag1+ is bonded to four Te2- atoms to form a mixture of corner and edge-sharing AgTe4 tetrahedra. There are a spread of Ag–Te bond distances ranging from 2.82–2.96 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Ba2+ and four Ag1+ atoms to form a mixture of distorted corner and edge-sharing TeBa3Ag4 pentagonal bipyramids. In the second Te2- site, Te2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(FeO2)2 by Materials Project

BaFe2O4 crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. Ba2+ is bonded in a distorted q6 geometry to nine O2- atoms. There are six shorter (2.93 Å) and three longer (3.18 Å) Ba–O bond lengths. Fe3+ is bonded to four O2- atoms to form corner-sharing FeO4 tetrahedra. There is one shorter (1.87 Å) and three longer (1.90 Å) Fe–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to three equivalent Ba2+ and two equivalent Fe3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+ and two equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗