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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ba(CuO)4 by Materials Project

Ba(CuO)4 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. All Ba–O bond lengths are 2.81 Å. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.80 Å. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.80 Å. O2- is bonded in a distorted water-like geometry to two equivalent Ba2+ and two Cu+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(YbS2)2 by Materials Project

Ba(YbS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Ba–S bond distances ranging from 3.16–3.36 Å. There are two inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded to six S2- atoms to form YbS6 octahedra that share corners with four equivalent YbS5 square pyramids and edges with four equivalent YbS6 octahedra. There are a spread of Yb–S bond distances ranging from 2.73–2.99 Å. In the second Yb3+ site, Yb3+ is bonded to five S2- atoms to form YbS5 square pyramids that share corners with four equivalent YbS6 octahedra and edges with two equivalent YbS5 square pyramids. The corner-sharing octahedra tilt angles range from 54–67°. There are a spread of Yb–S bond distances ranging from 2.64–2.97 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Yb3+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Ba2+, two equivalent Yb3+, and one S2- atom. The S–S bond length is 2.12 Å. In the third S2- site, S2- is bonded to two equivalent Ba2+ and three Yb3+ atoms to form distorted corner-sharing SBa2Yb3 trigonal bipyramids. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to two equivalent Ba2+, three equivalent Yb3+, and one S2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(YSe2)2 by Materials Project

Ba(YSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.34–3.53 Å. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing YSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Y–Se bond distances ranging from 2.85–2.94 Å. In the second Y3+ site, Y3+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing YSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Y–Se bond distances ranging from 2.83–2.91 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Ba2+ and three equivalent Y3+ atoms to form a mixture of distorted edge and corner-sharing SeBa2Y3 trigonal bipyramids. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Y3+ atoms. In the third Se2- site, Se2- is bonded to two equivalent Ba2+ and three equivalent Y3+ atoms to form a mixture of distorted edge and corner-sharing SeBa2Y3 square pyramids. In the fourth Se2- site, Se2- is bonded to two equivalent Ba2+ and three Y3+ atoms to form a mixture of distorted edge and corner-sharing SeBa2Y3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CoN)2 by Materials Project

Ba(CoN)2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. All Ba–N bond lengths are 3.23 Å. Co2+ is bonded in a distorted trigonal planar geometry to three equivalent N3- atoms. There is one shorter (1.76 Å) and two longer (1.81 Å) Co–N bond length. N3- is bonded in a 3-coordinate geometry to four equivalent Ba2+ and three equivalent Co2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(SbRu)2 by Materials Project

Ba(RuSb)2 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 Sb3- atoms. All Ba–Sb bond lengths are 3.64 Å. Ru2+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing RuSb4 tetrahedra. All Ru–Sb bond lengths are 2.60 Å. Sb3- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Ru2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AgO)2 by Materials Project

Ba(AgO)2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing BaO6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are two shorter (2.62 Å) and four longer (3.00 Å) Ba–O bond lengths. Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.10 Å. O2- is bonded to three equivalent Ba2+ and two equivalent Ag1+ atoms to form a mixture of distorted edge and corner-sharing OBa3Ag2 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(GdSe2)2 by Materials Project

Ba(GdSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.37–3.56 Å. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing GdSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–62°. There are a spread of Gd–Se bond distances ranging from 2.89–2.94 Å. In the second Gd3+ site, Gd3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing GdSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–62°. There are a spread of Gd–Se bond distances ranging from 2.88–2.95 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Gd3+ atoms. In the second Se2- site, Se2- is bonded to two equivalent Ba2+ and three equivalent Gd3+ atoms to form a mixture of distorted corner and edge-sharing SeBa2Gd3 square pyramids. In the third Se2- site, Se2- is bonded to two equivalent Ba2+ and three Gd3+ atoms to form a mixture of distorted corner and edge-sharing SeBa2Gd3 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded to two equivalent Ba2+ and three equivalent Gd3+ atoms to form a mixture of distorted corner and edge-sharing SeBa2Gd3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ErSe2)2 by Materials Project

Ba(ErSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.33–3.51 Å. There are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Er–Se bond distances ranging from 2.82–2.89 Å. In the second Er3+ site, Er3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Er–Se bond distances ranging from 2.83–2.90 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Er3+ atoms. In the second Se2- site, Se2- is bonded to two equivalent Ba2+ and three equivalent Er3+ atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 square pyramids. In the third Se2- site, Se2- is bonded to two equivalent Ba2+ and three Er3+ atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded to two equivalent Ba2+ and three equivalent Er3+ atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Machine Learning Reveals Memory of the Parent Phases in Ferroelectric Relaxors Ba(Ti$_{1-x}$,Zr x )O 3

Machine learning has been establishing its potential in multiple areas of condensed matter physics and materials science. Here, in this work, an unsupervised machine learning workflow is developed and used within a framework of first-principles-based atomistic simulations to investigate phases, phase transitions, and their structural origins in ferroelectric relaxors, Ba(Ti 1-x ,Zr x )O 3 . The applicability of the workflow is first demonstrated to identify phases and phase transitions in the parent compound, a prototypical ferroelectric BaTiO 3 . Then the workflow is applied for Ba(Ti 1-x ,Zrx)O 3 with x ≤ 0.25 to reveal i) that some of the compounds bear a subtle memory of BaTiO 3 phases beyond the point of the pinched phase transition, which could contribute to their enhanced electromechanical response; ii) the existence of peculiar phases with delocalized precursors of nanodomains—likely candidates for the controversial polar nanoregions; and iii) nanodomain phases for the largest concentrations of x.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Precise half-life determination of 131 Ba and 125 Xe

Barium-131 and Xenon-125 are valuable radioisotopes with numerous scientific and medical applications. Here, we produced both isotopes via proton irradiation of a cesium iodide (CsI) target at the Brookhaven Tandem Van de Graaff accelerator (BTVG). Following irradiation, we conducted systematic γ-ray spectroscopy measurements at the National Nuclear Data Center (NNDC) decay station using a calibrated High-Purity Germanium (HPGe) detector, collecting data over a 2-month period (spanning approximately 4.5 half-lives for 131 Ba). Through careful analysis of the characteristic γ-ray emissions from both isotopes, we determined the half-life of 131 Ba to be 11.55(6) days, which agrees with the previously evaluated value. For 125 Xe, we measured a half-life of 16.56(8) hours, slightly lower than the evaluated value.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Magnetic oxygen in transition metal oxides: A case study of Ba 2 CoO 4

Transition metal oxides (TMOs) exhibit exotic magnetic properties in both naturally formed and artificially structured materials, often difficult to understand in conventional wisdom. Magnetic insulator Ba 2 CoO 4 has mystified the community, because the CoO 4 tetrahedron is completely isolated with the nearest Co atoms far apart (~5 Å), making it impossible to account for long-range magnetic ordering seen experimentally using only Co. By theoretically investigating magnetism and relating our findings to experimental observations in bulk Ba 2 CoO 4 , we illustrate for the first time that the magnetic moment on oxygen atoms are the origin of the unexpected long-range magnetic ordering and low magnetic dimensionality. We find that the magnetic moment is not only localized on Co atoms, as assumed in all conventional data analysis, but also distributed on its tetrahedrally-coordinated O atoms. The total magnetic moment of the CoO 4 building block is 4.63μ B with the magnetic moment on Co being only 3.08μ B . Therefore, the magnetic building block is CoO 4 not Co. Furthermore, our first principles calculations are capable of explaining the origin of the unique magnetic response, including the presence of long-range magnetic ordering with two-dimensional character, and a one-dimensional magnetoelastic behavior. Having oxygen contribute to the magnetic moment will undoubtedly be identified as a universal property of magnetic TMOs, which will require a fresh look at conventional models of magnetism in TMOs.

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

London penetration depth of electron-irradiated Ba 0 . 47 K 0 . 53 Fe 2 As 2

We have characterized an electron-irradiated Ba 1-x K x Fe 2 As 2 (x = 0.53) single-crystal using two different experimental techniques: magneto-optic measurements and microwave measurements. The crystal has been measured before as well as after the 2.5 MeV electron irradiation process. After irradiation it was annealed in a number of steps, between 90 °C and 180 °C, and measured after each annealing step. Most microwave measurements were performed by means of a copper cavity, taking advantage of the TE 011 and TM 110 modes, allowing for the determination of the London penetration depths changes δλ ab (T) and δλ c (T), ie perpendicular and parallel to the sample c-axis. Appropriate equations, based on perturbation theory, were derived to calculate the penetration depths changes δλ ab and δλ c for a rectangular prism geometry. The sample showed a full recovery of its T c , however the observed behavior of δλ c and δλ ab was not monotonic vs annealing temperature, displaying a minimum of δλ c and δλ ab at 120 °C. In conclusion, this finding was confirmed by magneto-optic measurements, where besides verifying the sample uniformity and the absence of visible defects, the lower critical field H c1 of the Ba 1-x K x Fe 2 As 2 single-crystal was obtained and the London penetration depth λab(0) was calculated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Air separation via a two-step solar thermochemical cycle based on (Ba,La) x Sr 1-x FeO 3-δ : Thermodynamic analysis

A two-step solar thermochemical cycle was considered for air separation to produce N2 based on (Ba,La) x Sr 1-x FeO 3-δ perovskite reduction/oxidation (redox) reactions for A-site fractions of 0 ≤ x ≤ 0.2. The cycle steps encompassed (1) thermal reduction and O 2 release via concentrated solar input and (2) re-oxidation with air to uptake O 2 and produce high-purity N 2 . Thermogravimetry at temperatures between 400 and 1100 °C in atmospheres of 0.005 to 90% O 2 /Ar at 1 bar was performed to measure equilibrium nonstoichiometries. The compound energy formalism was applied to model redox thermodynamics for both Ba 2+ and La 3+ substitution. Non-linear regression was used to determine the empirical parameters based on the thermogravimetric measurements. The model was used to define partial molar reaction enthalpies and entropies and predicted equilibrium oxygen nonstoichiometry as functions of oxide stoichiometry, site fraction, temperature, and O 2 partial pressure. The thermodynamic analysis showed the materials are appealing for air separation at temperatures below 800 °C.

42 ENGINEERING↗
DOE OSTI2023

Uptake of Pb and the Formation of Mixed (Ba,Pb)SO 4 Monolayers on Barite During Cyclic Exposure to Lead-Containing Sulfuric Acid

Barite (BaSO 4 ) is a common additive in lead-acid batteries, where it acts as a nucleating agent to promote the reversible formation and dissolution of PbSO 4 during battery cycling. However, little is known about the molecular-scale mechanisms the nucleation and cyclic evolution of PbSO 4 over a battery’s lifetime. In this study, we explore the responses of a barite (001) surface to cycles of high and low lead concentrations in the presence of 100 mM sulfuric acid using in-situ atomic force microscopy and high-resolution X-ray reflectivity. Here we find that PbSO 4 epitaxial films readily nucleate on the barite surface, even from solutions that are undersaturated relative to bulk PbSO 4 . Despite this, barite (001) proves to be an ineffective nucleator of bulk PbSO 4 , as multilayer growth is suppressed even in highly supersaturated solutions. Instead, we find evidence that Pb 2+ ions can directly exchange with Ba 2+ to create mixed (Ba,Pb)SO 4 surfaces. These chemically mixed surfaces do not host PbSO4 monolayers as readily as pristine barite, and the original reactivity is not regained until a fresh surface is reestablished by aggressive etching. Our results can be partly explained by traditional models of Stranski-Krastanov (S-K) growth, in which monolayer films are stabilized by a reduction in surface energy, but multilayer growth is inhibited by epitaxial strain. Complementary density functional theory calculations confirmed the basic energetic-terms of traditional S-K models, but also showed evidence form more complex, thickness-dependent, energetics than would be predicted from the S-K models. The experimental results can be better understood by extending the S-K model to consider the formation of mixed surfaces and films, which can have reduced strain and interfacial energies relative to pure films, while also being stabilized by entropy of mixing. These insights into non-stoichiometric heteroepitaxy will enable better predictions of how barite affects PbSO 4 nucleation in battery environments.

25 ENERGY STORAGE↗
DOE OSTI2026

Ternary Phosphides Ba M 2 P 2 : Tailoring Crystal and Electronic Structures Enables Highly Efficient HER Electrocatalysis

Binary transition metal phosphides and their solid solutions have emerged as promising hydrogen evolution reaction (HER) catalysts. Although many research endeavors have adopted strategies to vary compositions to optimize catalytic performance, they mainly focus on binary structures, which represent only a small fraction of the abundant phase space of structure types among transition metal phosphides. Here, the largely unexplored class of ternary and multinary ordered phosphides in catalysis comprises two or more metals with quite different chemical nature, concealing the structure–property relationships essential for advancing catalyst design. Here, we explored phosphides crystallizing in one of the most abundant ordered intermetallic structure types, —the ThCr 2 Si 2 type, —where square nets of 3d transition metal M and P atoms are separated by layers of electropositive Ba cations. Four ternary BaM 2 P 2 (M = Fe, Fe/Cu, Fe/Ni, Ni) catalysts were synthesized and characterized. BaNi 2 P 2 showed high HER activity in acidic electrolyte, which required an overpotential, η 10 , of only 62 mV to drive current density j = –10 mA/cm 2 and high stability with a potential drop rate of 0.25 mV/h. BaNi 2 P 2 outperformed other Ni-based catalysts, such as Ni 2 P and Ni 5 P 4 . Notably, at current densities above –170 mA/cm 2 , BaNi 2 P 2 outperformed the standard Pt electrode measured under identical conditions. Electronic structure analysis revealed a volcano-type activity trend among the four BaM 2 P 2 catalysts based on their d-band center positions, highlighting the role of electropositive Ba cations in shifting the Ni-3d orbitals into an optimal position.

BaNi2P2↗
DOE OSTI2021

Double-Site Substitution of Ce into (Ba, Sr)MnO 3 Perovskites for Solar Thermochemical Hydrogen Production

Solar thermochemical hydrogen production (STCH) is a renewable alternative to hydrogen production using fossil fuels. While serial bulk experimental methods can accurately measure STCH performance, screening chemically complex materials systems for new promising candidates is more challenging. Here we identify double-site Ce-substituted (Ba,Sr)MnO 3 oxide perovskites as promising STCH candidates using a combination of bulk synthesis and high-throughput thin-film experiments. The Ce substitution on the B-site in 10H-BaMnO 3 and on the A-site in -SrMnO 3 leads to 2–3 times higher hydrogen production compared to CeO 2 , but these bulk single-site substituted perovskites suffer from incomplete reoxidation. Double-site Ce substitution on both A- and B-sites in (Ba,Sr)MnO 3 thin films increases Ce solubility and extends the stability of 10H and 3C structures, which is promising for their thermochemical reversibility. This study demonstrates a high-throughput experimental method for screening complex oxide materials for STCH applications.

08 HYDROGEN↗
DOE OSTI2026

Mixed Nd 4+/3+ and Cluster Magnetism in Hexagonal Perovskite 12R-Ba 4 NdMn 3 O 12−γ

Hexagonal perovskite oxides with 12R stacking host well-separated face-sharing octahedral metal trimers with short metal–metal distances, leading in some cases to large degrees of magnetic frustration and cluster magnetism. Introducing magnetic ions in proximity to these trimers can influence the degree of frustration and cluster magnetism, but the extent to which the magnetism can be tuned by varying neighboring metal cations remains an open question. In this work, we test the impacts of using Nd in proximity to Mn trimers in the hexagonal perovskite 12R-Ba 4 NdMn 3 O 12−γ . Given this stoichiometry, Nd should assume the 4+ oxidation state with a spin state of S = 1, which would be the first realization of Nd 4+ in an oxide environment. Through detailed bulk magnetic, X-ray absorption spectroscopic, and powder neutron diffraction (PND) measurements, we find that Nd 4+ is realized in this material, but there is also partial reduction to Nd 3+ , which is charge-balanced by O vacancies. Magnetometry measurements indicate an antiferromagnetic ordering temperature T N ≈ 16 K, and PND measurements reveal a surprising collinear antiferromagnetic structure with magnetic space group Pc2/m (no. 10.49 in BNS notation), which has not previously been seen in this class of materials. Our results represent a comprehensive analysis of the structural, electronic, and magnetic properties of 12R-Ba 4 NdMn 3 O 12−γ , showing the first observation of partial Nd 4+ in an oxide, and demonstrating that this structural class can host a broad range of magnetic structures which are not easily predicted based on compositional trends.

14 SOLAR ENERGY↗
DOE OSTI2020

Forensic tracers of exposure to produced water in freshwater mussels: a preliminary assessment of Ba, Sr, and cyclic hydrocarbons

Hydraulic fracturing is often criticized due in part to the potential degradation of ground and surface water quality by high-salinity produced water generated during well stimulation and production. This preliminary study evaluated the response of the freshwater mussel, Elliptio complanata, after exposure to produced water. A limited number of adult mussels were grown over an 8-week period in tanks dosed with produced water collected from a hydraulically fractured well. The fatty tissue and carbonate shells were assessed for accumulation of both inorganic and organic pollutants. Ba, Sr, and cyclic hydrocarbons indicated the potential to accumulate in the soft tissue of freshwater mussels following exposure to diluted oil and gas produced water. Exposed mussels showed accumulation of Ba in the soft tissue several hundred times above background water concentrations and increased concentrations of Sr. Cyclic hydrocarbons were detected in dosed mussels and principle component analysis of gas chromatograph time-of-flight mass spectrometer results could be a novel tool to help identify areas where aquatic organisms are impacted by oil and gas produced water, but larger studies with greater replication are necessary to confirm these results.

54 ENVIRONMENTAL SCIENCES↗