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DOE OSTI2020

Materials Data on CaLa(GeIr)4 by Materials Project

CaLa(IrGe)4 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All Ca–Ir bond lengths are 3.38 Å. All Ca–Ge bond lengths are 3.25 Å. La is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All La–Ir bond lengths are 3.38 Å. All La–Ge bond lengths are 3.27 Å. Ir is bonded to two equivalent Ca, two equivalent La, and four Ge atoms to form a mixture of distorted edge, corner, and face-sharing IrCa2La2Ge4 tetrahedra. There are two shorter (2.48 Å) and two longer (2.50 Å) Ir–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.60 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent La, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.68 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CaLa by Materials Project

CaLa is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ca is bonded to six equivalent Ca and six equivalent La atoms to form CaCa6La6 cuboctahedra that share corners with eighteen equivalent CaCa6La6 cuboctahedra, edges with six equivalent CaCa6La6 cuboctahedra, edges with twelve equivalent LaCa6La6 cuboctahedra, faces with eight equivalent CaCa6La6 cuboctahedra, and faces with twelve equivalent LaCa6La6 cuboctahedra. All Ca–Ca bond lengths are 3.78 Å. All Ca–La bond lengths are 3.83 Å. La is bonded to six equivalent Ca and six equivalent La atoms to form LaCa6La6 cuboctahedra that share corners with eighteen equivalent LaCa6La6 cuboctahedra, edges with six equivalent LaCa6La6 cuboctahedra, edges with twelve equivalent CaCa6La6 cuboctahedra, faces with eight equivalent LaCa6La6 cuboctahedra, and faces with twelve equivalent CaCa6La6 cuboctahedra. All La–La bond lengths are 3.78 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CaLa(CoO3)2 by Materials Project

CaLa(CoO3)2 is (Cubic) Perovskite-derived structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ca2+ is bonded to twelve equivalent O2- atoms to form CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent LaO12 cuboctahedra, and faces with eight equivalent CoO6 octahedra. All Ca–O bond lengths are 2.69 Å. La3+ is bonded to twelve equivalent O2- atoms to form LaO12 cuboctahedra that share corners with twelve equivalent LaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent CoO6 octahedra. All La–O bond lengths are 2.69 Å. Co+3.50+ is bonded to six equivalent O2- atoms to form CoO6 octahedra that share corners with six equivalent CoO6 octahedra, faces with four equivalent CaO12 cuboctahedra, and faces with four equivalent LaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Co–O bond lengths are 1.90 Å. O2- is bonded in a distorted linear geometry to two equivalent Ca2+, two equivalent La3+, and two equivalent Co+3.50+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Spin fluctuations in the 112-type iron-based superconductor Ca 0.82 La 0.18 Fe 0.96 Ni 0.04 As 2

Abstract We report time-of-flight inelastic neutron scattering (INS) investigations on the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC) Ca 0.82 La 0.18 Fe 0.96 Ni 0.04 As 2 (CaLa-112). In comparison to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure (space group I 4 / m m m ) at room temperature and an in-plane stripe-type antiferromagnetic (AF) order at low temperature, the 112 system has a noncentrosymmetric structure (space group P 2 1 ) with additional zigzag arsenic chains between Ca/La layers and a magnetic ground state with similar wavevector Q A F but different orientations of ordered moments in the parent compounds. Our INS study clearly reveals that the in-plane dispersions and the bandwidth of spin excitations in the superconducting CaLa-112 closely resemble to those in 122 systems. While the total fluctuating moments ⟨ m 2 ⟩ ≈ 4.6 ± 0.2 μ B 2 /Fe are larger than 122 system, the dynamic correlation lengths are similar ( ξ ≈ 10 Å). These results suggest that superconductivity in iron arsenides may have a common magnetic origin under similar magnetic exchange couplings with a dual nature from local moments and itinerant electrons, despite their different magnetic patterns and lattice symmetries.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2025

Flux-Assisted Boron Chalcogen Mixture (BCM) Method for Synthesizing Mixed Chalcogenide Semiconductors (AkRE 2 Si 2 Se x S 8– x and CaRE 2 Si 2 Se 8 ) ( Ak = Ca and Sr; RE = La, Ce, Pr, Nd, and Sm): Investigation of Their Magnetic and Optical Properties

We report a detailed structural analysis of a series of ten quaternary rare-earth-containing seleno-thiosilicates AkRE 2 Si 2 Se x S 8-x and selenosilicates, CaRE 2 Si 2 Se 8 (Ak = Ca and Sr; RE = La, Ce, Pr, Nd, and Sm). Single crystals were obtained by using the flux-assisted boron chalcogen mixture (BCM) method and single crystal X-ray diffraction was used to determine their structures. All members of the AkRE 2 Si 2 Se x S 8-x and CaRE 2 Si 2 Se 8 series crystallize in the space group R$\bar{3}$c (space group number 167) of the trigonal crystal system. The single-crystal X-ray diffraction analysis revealed a strong preference for Se/S atoms to occupy one vs. the other of the two available sites. Polycrystalline samples were used for magnetic susceptibility and UV–visible diffuse reflectance measurements. Magnetic measurements show that CaCe₂Si₂Se₁.₇₃S₆.₂₇ and CaNd₂Si₂Se₂.₅S₅.₅ are paramagnetic with negative Weiss constants (θ = –60.1 and –26.2). Diffuse reflectance analysis gives optical band gaps of 2.7(1) eV (CaLa₂Si₂Se₂.₃₈S₅.₆₂), 2.2(1) eV (CaCe₂Si₂Se₁.₇₃S₆.₂₇), 2.5(1) eV (CaNd₂Si₂Se₂.₅S₅.₅), and 2.0(1) eV (CaCe₂Si₂Se₈), consistent with density functional theory calculations. By partially or fully replacing S sites with Se it was possible to achieve band gap tuning. Photoluminescence behavior was also investigated for CaCe 2 Si 2 Se 1.73 S 6.27 via irradiation with 375 nm ultraviolet light.

BCM method↗

DOE OSTI2022

Spectroscopic investigation of historical uranium glasses

Here, we present spectroscopic investigations of uranium in two historical glasses. A 1920's-1930's Art Deco (Bagley Carnival) green soda-lime-silica uranium glass bowl and a 1930's-1940's (Thomas Webb) yellow full lead crystal uranium glass vase were studied using optical absorption spectroscopy, XRF and SEM-EDX, X-band EPR and High- Energy Resolution Fluorescence-Detected (HERFD)-XANES. Uranium speciation may be different in the two glasses. Uranium occurs as uranyl groups (UO 2 2+ ) with minority reduced uranium species, mostly as U(V), more important in the Webb glass than in the Bagley glass. The differences between the two glasses arise from the fining procedure and result from the presence of other multivalent elements and differences in base glass composition. Electron Paramagnetic Resonance (EPR) spectra show the presence of an incipient signal close to g~2, partially annealed by heating to 550 °C, which we assign to a small concentration of radiation-induced defects caused by uranium decay. The presence of multivalent glass components in addition to U (As + Cu + Fe in the Bagley glass and Sb + Fe in the Webb glass) can trap the electron-hole pairs generated by the presence of uranium. This may explain the weakness of this signal in these glasses that anyway received a limited radiation dose since their fabrication. The low activity of these glasses, close to the background radiation, confirms that there is no danger to exhibiting them in museums.

36 MATERIALS SCIENCE↗

DOE OSTI2022

The Melampsora americana Population on Salix purpurea in the Great Lakes Region Is Highly Diverse with a Contributory Influence of Clonality

Shrub willows (Salix spp.) are emerging as a viable lignocellulosic, second-generation bioenergy crop with many growth characteristics favorable for marginal lands in New York State and surrounding areas. Willow rust, caused by members of the genus Melampsora, is the most limiting disease of shrub willow in this region and remains extremely understudied. In this study, genetic diversity, genetic structure, and pathogen clonality were examined in Melampsora americana over two growing seasons via genotyping-by-sequencing to identify single-nucleotide polymorphism markers. In conjunction with this project, a reference genome of rust isolate R15-033-03 was generated to aid in variant discovery. Sampling between years allowed regional and site-specific investigation into population dynamics, in the context of both wild and cultivated hosts within high-density plantings. This work revealed that this pathogen is largely panmictic over the sampled areas, with few sites showing moderate genetic differentiation. These data support the hypothesis of sexual recombination between growing seasons because no genotype persisted across the two years of sampling. Additionally, clonality was determined as a driver of pathogen populations within cultivated fields and single shrubs; however, there is also evidence of high genetic diversity of rust isolates in all settings. This work provides a framework for M. americana population structure in the Great Lakes region, providing crucial information that can aid in future resistance breeding efforts.

Plant Sciences↗

DOE OSTI2022

Informing Nature-based Climate Solutions for the United States with the best-available science

Nature-based Climate Solutions (NbCS) are managed alterations to ecosystems designed to increase carbon sequestration or reduce greenhouse gas emissions. While they have growing public and private support, the realizable benefits and unintended consequences of NbCS are not well understood. At regional scales where policy decisions are often made, NbCS benefits are estimated from soil and tree survey data that can miss important carbon sources and sinks within an ecosystem, and do not reveal the biophysical impacts of NbCS for local water and energy cycles. The only direct observations of ecosystem-scale carbon fluxes, for example, by eddy covariance flux towers, have not yet been systematically assessed for what they can tell us about NbCS potentials, and state-of-the-art remote sensing products and land-surface models are not yet being widely used to inform NbCS policymaking or implementation. As a result, there is a critical mismatch between the point- and tree-scale data most often used to assess NbCS benefits and impacts, the ecosystem and landscape scales where NbCS projects are implemented, and the regional to continental scales most relevant to policymaking. Here, we propose a research agenda to confront these gaps using data and tools that have long been used to understand the mechanisms driving ecosystem carbon and energy cycling, but have not yet been widely applied to NbCS. Furthermore, we outline steps for creating robust NbCS assessments at both local to regional scales that are informed by ecosystem-scale observations, and which consider concurrent biophysical impacts, future climate feedbacks, and the need for equitable and inclusive NbCS implementation strategies. We contend that these research goals can largely be accomplished by shifting the scales at which pre-existing tools are applied and blended together, although we also highlight some opportunities for more radical shifts in approach.

54 ENVIRONMENTAL SCIENCES↗