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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ba(AgS)2 by Materials Project

Ba(AgS)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent S2- atoms to form BaS6 octahedra that share corners with twelve equivalent AgS4 tetrahedra, edges with six equivalent BaS6 octahedra, and edges with six equivalent AgS4 tetrahedra. All Ba–S bond lengths are 3.16 Å. Ag1+ is bonded to four equivalent S2- atoms to form AgS4 tetrahedra that share corners with six equivalent BaS6 octahedra, corners with six equivalent AgS4 tetrahedra, edges with three equivalent BaS6 octahedra, and edges with three equivalent AgS4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–54°. There are one shorter (2.69 Å) and three longer (2.70 Å) Ag–S bond lengths. S2- is bonded to three equivalent Ba2+ and four equivalent Ag1+ atoms to form a mixture of distorted corner and edge-sharing SBa3Ag4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ag Alloying in Cu 2– y Ag y Ba(Ge,Sn)Se 4 Films and Photovoltaic Devices

Trigonal Cu 2 BaGe 1–x Sn x Se 4 (CBGTSe) has recently gained interest as a potential photovoltaic absorber to target mitigation of antisite defect formation in Cu 2 ZnSn(S,Se) 4 . This study examines partial substitution of Cu by Ag as a potential approach to tune the properties of Ag-incorporated CBGTSe in the following aspects: 1) phase stability and crystal structure as a function of Ag content; 2) film morphology and grain structure; 3) charge carrier properties; 4) band positions; and 5) charge carrier kinetics and recombination. Up to 20% of Cu can be substituted by Ag in CBGTSe, while above 20% a phase mixture appears. Increasing Ag content induces larger average grain size and reduced hole carrier densities. In contrast, photoelectron spectroscopy and photoluminescence measurements reveal negligible impact of Ag substitution on ionization potential (≈5.4 eV) and electron affinity (≈3.7 eV). Also, Ag content offers negligible impact on carrier lifetimes (few ns). Consistent with these fundamental properties, solar cells based on two different Ag/(Ag + Cu) ratios (≈0% and ≈20%) show comparable power conversion efficiencies (≈2.7–2.8%). Finally, these results indicate that CBGTSe films and solar cells may be less sensitive to Ag substitution compared to Cu 2 ZnSn(S,Se) 4 , at least at the current level of absorber and device optimization.

14 SOLAR ENERGY↗
DOE OSTI2021

Impact of Stabilizing Cations on Lithium Intercalation in Tunneled Manganese Oxide Cathodes

Stabilizing cations such as K + , Ba 2+ , and Ag + are known to provide charge neutrality and enhance structural stability in low-cost tunneled manganese dioxide (MnO 2 ) cathodes for Li ion batteries. However, a fundamental understanding of the role of these cations in the electrochemical performance of tunneled MnO 2 cathodes remains unclear, especially at low stabilizing cation concentrations. Here, we employ density functional theory (DFT + U) calculations to reveal the impact of stabilizing potassium cation (K + ) concentration on the structural stability, electronic properties, and kinetics of lithium transport in 2 x 2 tunneled manganese oxide (α-K y Mn 8 O 16 , at y = 0, 1, and 2) battery cathodes during lithium intercalation. Specifically, we provide insights into the effect of K + ions on several critical factors governing the electrochemical storage performance of tunneled MnO2 cathodes, including (a) energetically favorable Li+ host sites, (ii) Li + and electron transport capabilities, (iii) optimal intercalation pathways, crystal distortion, microstructural stability, and tunneled-to-layer phase transformation as a function of lithium content, and (iv) cell output voltage profile. Interestingly, we find that low K + concentrations (y ≤ 1) yield partially cation-deficient tunnels in the MnO 2 cathode. Such unique tunnel structures in the cathode enable (a) low kinetic barriers for Li transport, (b) excellent thermodynamic stability of the tunneled structure even at a high Li + loading (up to ~ 0.625 Li/Mn), and (c) good electronic conductivity facilitated by Jahn-Teller distortions; all of which are critical for achieving high capacity batteries with enhanced rate capability. Additionally, these results provide perspectives to design low-cost transition metal oxide cathodes for high-performance Li-ion batteries with excellent cycle life.

25 ENERGY STORAGE↗
DOE OSTI2024

Uncovering fast solid-acid proton conductors based on dynamics of polyanion groups and proton bonding strength

Achieving high proton conductivity in inorganic solids is key for advancing many electrochemical technologies, including low-energy nano-electronics and energy-efficient fuel cells and electrolyzers. A quantitative understanding of the physical traits of a material that regulate proton diffusion is necessary for accelerating the discovery of fast proton conductors. In this work, we have mapped the structural, chemical and dynamic properties of solid acids to the elementary steps of the Grotthuss mechanism of proton diffusion. Our approach combines ab initio molecular dynamics simulations, analysis of phonon spectra and atomic structure calculations. We have identified the donor–hydrogen bond lengths and the acidity of polyanion groups as key descriptors of local proton transfer and the vibrational frequencies of the cation framework as the key descriptor of lattice flexibility. The latter facilitates rotations of polyanion groups and long-range proton migration in solid acid proton conductors. The calculated lattice flexibility also correlates with the experimentally reported superprotonic transition temperatures. Using these descriptors, we have screened the Materials Project database and identified potential solid acid proton conductors with monovalent, divalent and trivalent cations, including Ag + , Sr 2+ , Ba 2+ and Er 3+ cations, which go beyond the traditionally considered monovalent alkali cations (Cs + , Rb + , K + , and NH 4 + ) in solid acids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Synthesis, Structures, and Transport Properties of Quaternary Ba–Ag– Tr –As Materials ( Tr = Ga, In)

The synthesis, structures, and properties of two quaternary barium–arsenide materials are presented. The first, Ba 4 Ag 2.3 In 1.7 As 8 , is a novel material with the monoclinic unit cell ( P 2 1 / m space group). The layered crystal structure of Ba 4 Ag 2.3 In 1.7 As 8 may be considered a lower‐symmetry, distorted analog of the LaCuSb 2 structure. The structure features a rare As fragment, cis‐trans As chains along the [010] direction. Large crystals of Ba 4 Ag 2.3 In 1.7 As 8 can be grown from Bi flux and are used for subsequent transport property measurements. Electrical resistivity and heat capacity properties are reported, establishing Ba 4 Ag 2.3 In 1.7 As 8 as a metallic phase. The second material, Ba 4 AgGa 5 As 8 , is a 3D material that crystallizes in the orthorhombic unit cell (noncentrosymmetric and polar Iba 2 space group). Expanding upon its original discovery, the optimized synthetic profile for single‐phase polycrystalline samples as well as transport properties relevant to thermoelectric applications are presented. Ba 4 AgGa 5 As 8 exhibits a high Seebeck coefficient of 290 μV K −1 at room temperature, indicative of lower carrier concentrations typical for nonmetallic phases. Electrical resistivity measurements also affirm conventional semiconducting behavior for Ba 4 AgGa 5 As 8 .

Kyveryga, Victoria [Department of Chemistry Iowa S↗
DOE OSTI2020

Materials Data on Ba2(AlAg)5 by Materials Project

Ba2(AgAl)5 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 7-coordinate geometry to two equivalent Ba, nine Ag, and six Al atoms. Both Ba–Ba bond lengths are 4.11 Å. There are a spread of Ba–Ag bond distances ranging from 3.44–4.08 Å. There are two shorter (3.58 Å) and four longer (3.84 Å) Ba–Al bond lengths. In the second Ba site, Ba is bonded in a 9-coordinate geometry to two equivalent Ba, ten Ag, and nine Al atoms. There are a spread of Ba–Ag bond distances ranging from 3.55–4.13 Å. There are a spread of Ba–Al bond distances ranging from 3.54–3.90 Å. There are three inequivalent Ag sites. In the first Ag site, Ag is bonded in a 11-coordinate geometry to four Ba, three Ag, and four equivalent Al atoms. There are one shorter (2.93 Å) and two longer (3.08 Å) Ag–Ag bond lengths. There are two shorter (2.66 Å) and two longer (2.79 Å) Ag–Al bond lengths. In the second Ag site, Ag is bonded in a 11-coordinate geometry to four Ba, two equivalent Ag, and five Al atoms. There are a spread of Ag–Al bond distances ranging from 2.67–2.82 Å. In the third Ag site, Ag is bonded in a 11-coordinate geometry to three Ba, two equivalent Ag, and six Al atoms. There are four shorter (2.72 Å) and two longer (3.03 Å) Ag–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 5-coordinate geometry to three Ba, five Ag, and one Al atom. The Al–Al bond length is 2.77 Å. In the second Al site, Al is bonded in a 2-coordinate geometry to three Ba, four Ag, and four equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Superconductivity with T c ≈ 7 K under pressure for Cu- and Au-doped BaFe 2 As 2

It is noteworthy that chemical substitution of BaFe 2 As 2 (122) with the noble elements Cu and Au gives superconductivity with a maximum T c ≈ 3 K, while Ag substitution (Ag-122) stays antiferromagnetic. For Ba(Fe 1–x TM x ) 2 As 2 , TM = Cu, Au, or Ag, and by doping an amount of x = 0.04, a-lattice parameter slightly increases (0.4%) for all TM dopants, while c-lattice decreases (–0.2%) for TM = Cu, barely moves (0.05%) for Au, and increases (0.2%) for Ag. Despite the naive expectation that the noble elements of group 11 should affect the quantum properties of 122 similarly, they produce significant differences extending to the character of the ground state. For the Ag-122 crystal, evidence of only a filamentary superconductivity is noted with pressure. However, for Au and Cu doping (x ≈ 0.03) we find a substantial improvement in the superconductivity, with T c increasing to 7 K and 7.5 K, respectively, under 20 kbar of pressure. As with the ambient pressure results, the identity of the dopant therefore has a substantial impact on the ground state properties. Further, density functional theory calculations corroborate these results and find evidence of strong electronic scattering for Au and Ag dopants, while Cu is comparatively less disruptive to the 122 electronic structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Ba(AgGe)2 by Materials Project

Ba(AgGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Ag and eight equivalent Ge atoms. All Ba–Ag bond lengths are 3.59 Å. All Ba–Ge bond lengths are 3.54 Å. Ag is bonded in a 12-coordinate geometry to four equivalent Ba and four equivalent Ge atoms. All Ag–Ge bond lengths are 2.75 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Ag, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AgSn)2 by Materials Project

Ba(AgSn)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Ag and eight equivalent Sn atoms. All Ba–Ag bond lengths are 3.79 Å. All Ba–Sn bond lengths are 3.77 Å. Ag is bonded in a 12-coordinate geometry to four equivalent Ba and four equivalent Sn atoms. All Ag–Sn bond lengths are 2.84 Å. Sn is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Ag, and one Sn atom. The Sn–Sn bond length is 2.92 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Ag3O2)2 by Materials Project

Ba(Ag3O2)2 crystallizes in the orthorhombic Pnna space group. The structure is three-dimensional. Ba2+ is bonded to six O2- atoms to form edge-sharing BaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.65–2.93 Å. There are four inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a linear geometry to two O2- atoms. There are one shorter (2.12 Å) and one longer (2.14 Å) Ag–O bond lengths. In the second Ag1+ site, Ag1+ is bonded in a linear geometry to two O2- atoms. There are one shorter (2.10 Å) and one longer (2.11 Å) Ag–O bond lengths. In the third Ag1+ site, Ag1+ is bonded in a 2-coordinate geometry to four O2- atoms. There are two shorter (2.38 Å) and two longer (3.00 Å) Ag–O bond lengths. In the fourth Ag1+ site, Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.12 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ba2+ and three Ag1+ atoms to form a mixture of corner and edge-sharing OBa2Ag3 trigonal bipyramids. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and four Ag1+ atoms.

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(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 BaCu2(AgO2)2 by Materials Project

BaCu2(AgO2)2 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 2.78 Å. Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.07 Å. Cu2+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.79 Å. O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ag1+, and one Cu2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaAg2(HgO2)2 by Materials Project

BaAg2(HgO2)2 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. Ba2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. All Ba–O bond lengths are 2.92 Å. Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.12 Å. Hg2+ is bonded in a distorted linear geometry to four equivalent O2- atoms. There are two shorter (2.05 Å) and two longer (2.90 Å) Hg–O bond lengths. O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ag1+, and two equivalent Hg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Exploration, Prediction, and Experimental Verification of Structure and Optoelectronic Properties in I 2 -Eu-IV-X 4 (I = Li, Cu, Ag; IV = Si, Ge, Sn; X = S, Se) Chalcogenide Semiconductors

Recently, there has been extensive research into photovoltaic, thermoelectric, and nonlinear optical applications of chalcogenide semiconductors within the large set of defect-resistant I 2 -II-IV-X4 (I = Li, Cu, Ag; II = Ba, Sr, Eu, Pb; IV = Si, Ge, Sn; X = S, Se) compounds. Five Eu-including compounds have previously been reported within this family, but a comparative study of possible structures and electronic properties of all 18 Eu-based combinations is still absent. Herein, we use hybrid density functional theory to study rare-earth-including I 2 -II-IV-X 4 semiconductors with Eu on the II site, in order to further understand this family and test the geometric tolerance factor approach (reported in our previous work) as a tool for predicting potential stable structures. We investigate how the exchange mixing parameter of the HSE06 density functional, α, affects the energetic positions of electronic levels, especially of the localized f-electron orbitals near the band edges of the extended semiconductor structures, using literature photoemission and band gap data of EuS for comparison. Lowest-energy quaternary structure candidates, energy band structures, and densities of states are computationally predicted for all 18 materials. Based on its predicted photovoltaics-relevant band gap, the previously unknown compound Cu 2 EuSnSe 4 was selected and synthesized. Furthermore, the experimental structure, lattice parameters, and band gap of Cu 2 EuSnSe 4 are consistent with the computational predictions, confirming a 1.55 eV band gap.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

Multi-Line Gamma-Ray Spectrometer Performance of a Si(Li) Detector Stack

Experimental data is presented which for the first time displays multi-line spectrometer performance of a Si(Li) detector stack at elevated temperature. The stack consists of four elements, each with a 2 cm diameter active area. Ba-133 and Ag-110m spectra are obtained using various techniques to enhance the peak-to-background ratio. Spectral data are shown as a function of temperature (94 K less than or equal to T less than or equal to 230 K) using optimized peak shaping.

Hubbard, G. Scott↗
NASA NTRS1995

Multi-Line Gamma-Ray Spectrometer Performance of a Si(Li) Detector Stack

Experimental data is presented which for the first time displays multi-line spectrometer performance of a Si(Li) detector stack at elevated temperature. The stack consists of four elements, each with a 2 cm diameter active area. Ba-133 and Ag-110m spectra are obtained using various techniques to enhance the peak-to-background ratio. Spectral data are shown as a function of temperature (94 K less than or = T less than or = 230 K) using optimized peak shaping.

Hubbard, G. Scott↗
DOE OSTI2024

Discovery of Stable Surfaces with Extreme Work Functions by High‐Throughput Density Functional Theory and Machine Learning

Abstract The work function is the key surface property that determines the energy required to extract an electron from the surface of a material. This property is crucial for thermionic energy conversion, band alignment in heterostructures, and electron emission devices. This work presents a high‐throughput workflow using density functional theory (DFT) to calculate the work function and cleavage energy of 33,631 slabs (58,332 work functions) that are created from 3,716 bulk materials. The number of calculated surface properties surpasses the previously largest database by a factor of ≈27. Several surfaces with an ultra‐low (<2 eV) and ultra‐high (>7 eV) work function are identified. Specifically, the (100)‐Ba‐O surface of BaMoO 3 and the (001)‐F surface of Ag 2 F have record‐low (1.25 eV) and record‐high (9.06 eV) steady‐state work functions. Based on this database a physics‐based approach to featurize surfaces is utilized to predict the work function. The random forest model achieves a test mean absolute error (MAE) of 0.09 eV, comparable to the accuracy of DFT. This surrogate model enables rapid predictions of the work function (≈ 10 5 faster than DFT) across a vast chemical space and facilitates the discovery of material surfaces with extreme work functions for energy conversion and electronic device applications.

97 MATHEMATICS AND COMPUTING↗