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DOE OSTI2018

High energy storage properties of (Ni1/3Nb2/3)4+ complex-ion modified (Ba0.85Ca0.15)(Zr0.10Ti0.90)O3 ceramics

Highlights: • BCZT-xNN ceramics showed single phase perovskite structure without an obvious second phase after adding NN, and exhibited both good temperature (−55 to 160 °C) and frequency (10{sup 2}–10{sup 7} Hz) stability. • The highest energy storage density can reach 0.66 J/cm{sup 3} and the energy efficiency is 88.1% was achieved in x = 0.3. • The environmental friendly (lead-free) BCZT-xNN ceramics are good candidate for application in energy storage devices. • This paper also developes a new method to obtain high energy storage density and efficiency of ceramic capacitor, which aims to adjust the T{sub c} of ceramics far below room temperature. - Abstract: In this study, paraelectric ceramics, (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90}){sub 1-x}(Ni{sub 1/3}Nb{sub 2/3}){sub x}O{sub 3,} abbreviated as BCZT-xNN (with x = 0.1, 0.2, 0.3, 0.4) were prepared via a solid-state reaction method. By introducing a B-site complex-ion, (Ni{sub 1/3}Nb{sub 2/3}){sup 4+}, the Curie temperature of the ceramic could be reduced to below room temperature. The effects of this B-site (Ni{sub 1/3}Nb{sub 2/3}){sup 4+} complex-ion substitution on the phase structure, surface microstructure as well as the dielectric, ferroelectric, and energy storage properties of the ceramic were systematically investigated. After adding NN, BCZT-xNN shows a single phase perovskite structure without evidence of a second phase . In addition, we observed high stability with respect to both temperature (−55 to 160 °C) and frequency (10{sup 2}–10{sup 7} Hz). Doping with NN produces slim polarization-electric field hysteresis loops and enhanced energy storage properties, while the efficiency decreases. When x = 0.3, the highest energy storage density reached 0.66 J/cm{sup 3} for a high electric field (20 kV/mm), and the respective energy efficiency was 88.1%. These properties indicate that the environmental friendly BCZT-xNN ceramics are promising candidates for commercial energy storage devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Reinforcing cycling stability and rate capability of LiNi0.5Mn1.5O4 cathode by dual-modification of coating and doping of a fast-ion conductor

Highlights: • Li{sub 2}SiO{sub 3}-modified LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} with well-defined octahedral morphology have been controllably obtained. • The combination of the modification of fast ions conductor and solid state method will be an optional method. • The cyclic performance and rate capability of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4}-based materials have been significantly improved. - Abstract: A simple solid state method was utilized to synthesize excellent spinel Li{sub 2}SiO{sub 3}-modified LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} cathodes. Dual-modification of coating and doping of fast-ion conductor Li{sub 2}SiO{sub 3} leads to stable crystal structure and additional three-dimensional (3-D) channels for Li{sup +}-ion diffusion, and protects the electrode surface from electrolyte attack. The Li{sub 2}SiO{sub 3}-modified material possesses coexistence of ordered P4{sub 3}32 and disordered Fd-3m phases. As a result of improved structure, morphology and conductivity, the Li{sub 2}SiO{sub 3}-modified LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} shows more superior cyclic performance, rate capability and high temperature stability than the pristine: capacity retention of 95.17% at 0.1 C after 100 cycles vs. that of 79.23%; rate capability of 130–89.1 mAh g{sup −1} at 0.1–10 C vs. that of 120–57.6 mAh g{sup −1}; and high temperature capacity retention of 99.42% at 0.1 C vs. that of 79.59%. Our study provides a facile approach to stabilize crystal structure, optimize morphology and conductivity, and thus enhance electrochemical performance of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4}-based materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2014

Dead layer on silicon p-i-n diode charged-particle detectors

Abstract Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrinomass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by discussion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

Dead layer↗

DOE OSTI2016

All-optical materials design of chiral edge modes in transition-metal dichalcogenides

Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. As a result, we develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS 2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Identifying Bayesian optimal experiments for uncertain biochemical pathway models

Abstract Pharmacodynamic (PD) models are mathematical models of cellular reaction networks that include drug mechanisms of action. These models are useful for studying predictive therapeutic outcomes of novel drug therapies in silico. However, PD models are known to possess significant uncertainty with respect to constituent parameter data, leading to uncertainty in the model predictions. Furthermore, experimental data to calibrate these models is often limited or unavailable for novel pathways. In this study, we present a Bayesian optimal experimental design approach for improving PD model prediction accuracy. We then apply our method using simulated experimental data to account for uncertainty in hypothetical laboratory measurements. This leads to a probabilistic prediction of drug performance and a quantitative measure of which prospective laboratory experiment will optimally reduce prediction uncertainty in the PD model. The methods proposed here provide a way forward for uncertainty quantification and guided experimental design for models of novel biological pathways.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2023

MHD modeling of shattered pellet injection in JET

Abstract Nonlinear 3D MHD simulations of shattered-pellet injection (SPI) in JET show prototypical SPI-driven disruptions using the M3D-C1 and NIMROD extended-MHD codes. Initially, radiation-driven thermal quenches are accelerated by MHD activity as the pellet crosses rational surfaces, leading to a radiation spike, global stochasticization of the magnetic field, and a complete thermal quench. Eventually, current quenches, preceded by a current spike are seen as the Ohmic heating becomes equal to the radiative cooling. The results are qualitatively similar for both a single monolithic pellet, pencil-beam model, and a realistic shatter to represent the SPI plume. A scan in viscosity from 500 to 2000 m 2 s −1 for MHD simulations finds that reducing viscosity increases MHD activity and decreases thermal quench time slightly. A realistic cloud of fragments modeling shows that mixed-D–Ne pellet travels deeper into the plasma core before the thermal quench. At the slow pellet speeds, the pellet is found to be moving slowly enough inward that even the 5% neon in the mixed pellet is enough to effectively radiate the thermal energy available. Radiation toroidal peaking is predicted to be at levels consistent with experimental observations and reduced as the pellet travels deeper into the plasma. These simulations lay the ground work for more-sophisticated validative and predictive modeling of SPI in JET using both M3D-C1 and NIMROD.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2020

Skyrmion pinball and directed motion on obstacle arrays

Abstract We examine skyrmions interacting with a square array of obstacles under ac drives applied in one or two directions. For a single direction of ac driving, we find that the Magnus force in conjunction with the obstacle interactions can create elliptical skyrmion orbits of increasing size, leading to localized phases, chaotic phases, and translating or ratcheting orbits. Under two ac drives that are out of phase by 90° and applied in two directions, the skyrmions form localized commensurate orbits that encircle an integer number of obstacles, similar to the electron pinball effect observed for electrons in antidot lattices. As a function of ac amplitude, Magnus force strength, and obstacle size, we find that chaotic scattering regimes and directed motion can emerge even in the absence of asymmetry in the substrate. The directed motion follows different symmetry axes of the periodic substrate, and we observe a variety of reversed ratchet effects. The Magnus force in the skyrmion system produces a significantly larger number of directed motion regimes than are exhibited by overdamped systems. We discuss how these results could be used to move skyrmions in a controlled way for possible applications.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2019

Fast-rising blue optical transients and AT2018cow following electron-capture collapse of merged white dwarfs

We suggest that fast-rising blue optical transients (FBOTs) and the brightest event of the class, AT2018cow, result from an electron-capture collapse to a neutron star following the merger of a massive ONeMg white dwarf (WD) with another WD. Two distinct evolutionary channels lead to the disruption of the less-massive WD during the merger and the formation of a shell-burning non-degenerate star incorporating the ONeMg core. During the shell-burning stage, a large fraction of the envelope is lost to the wind, while mass and angular momentum are added to the core. As a result, the electron-capture collapse occurs with a small envelope mass, after ~10 2 –10 4 yr. During the formation of a neutron star, as little as |${\sim } 10^{-2} \, \mathrm{M}_\odot$| of the material is ejected at the bounce-off with mildly relativistic velocities and total energy of about a few 10 50 erg. This ejecta becomes optically thin on a time-scale of days – this is the FBOT. During the collapse, the neutron star is spun up and the magnetic field is amplified. The ensuing fast magnetically dominated relativistic wind from the newly formed neutron star shocks against the ejecta, and later against the wind. The radiation-dominated forward shock produces the long-lasting optical afterglow, while the termination shock of the relativistic wind produces the high-energy emission in a manner similar to pulsar wind nebulae. If the secondary WD was of the DA type, the wind will likely have |${\sim } 10^{-4} \, \mathrm{M}_\odot$| of hydrogen; this explains the appearance of hydrogen late in the afterglow spectrum. The model explains many of the puzzling properties of FBOTs/AT2018cow: host galaxies, a fast and light anisotropic ejecta producing a bright optical peak, afterglow high-energy emission of similar luminosity to the optical, and late infrared features.

Astronomy & Astrophysics↗

DOE OSTI2022

Generalized Lapse Rate Formulas for Use in Entraining CAPE Calculations

Abstract Common assumptions in temperature lapse rate formulas for lifted air parcels include neglecting mixing, hydrostatic balance, the removal of all condensate once it forms (pseudoadiabatic), and/or the retention of all condensate within the parcel (adiabatic). These formulas are commonly derived from the conservation of entropy, which leads to errors when nonequilibrium mixed-phase condensate is present. To evaluate these assumptions, a new general lapse rate formula is derived from an expression for energy conservation, rather than entropy conservation. This new formula incorporates mixing of the parcel with its surroundings, relaxes the hydrostatic assumption, allows for nonequilibrium mixed-phase condensate, and can be formulated for pseudoadiabatic or adiabatic ascent. The new formula is shown to exactly conserve entropy for reversible ascent. Predictions by the new formula are compared to that of older and less general formulas. The errors in previous formulas arise from the assumption of hydrostatic balance, which results in considerable warm biases due to the neglect of the energy sink from buoyancy. Predictions of ascent with entrainment using the new formula are then compared to parcel properties along trajectories in large eddy simulations. Simulated parcel properties are better predicted by the formula using a diluted analogy to adiabatic ascent, wherein condensate is diluted at the same rate as other parcel properties, than by the diluted analogy to pseudoadiabatic ascent, wherein all condensate is removed. These results suggest that CAPE should be computed with adiabatic, rather than pseudoadiabatic, parcel ascent.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2025

Exascale workflow applications and middleware: An ExaWorks retrospective

Exascale computers offer transformative capabilities to combine data-driven and learning-based approaches with traditional simulation applications to accelerate scientific discovery and insight. However, these software combinations and integrations are difficult to achieve due to the challenges of coordinating and deploying heterogeneous software components on diverse and massive platforms. Here, we present the ExaWorks project, which addresses many of these challenges. We developed a workflow Software Development Toolkit (SDK), a curated collection of workflow technologies that can be composed and interoperated through a common interface, engineered following current best practices, and specifically designed to work on HPC platforms. ExaWorks also developed PSI/J, a job management abstraction API, to simplify the construction of portable software components and applications that can be used over various HPC schedulers. The PSI/J API is a minimal interface for submitting and monitoring jobs and their execution state across multiple and commonly used HPC schedulers. We also describe several leading and innovative workflow examples of ExaWorks tools used on DOE leadership platforms. Furthermore, we discuss how our project is working with the workflow community, large computing facilities, and HPC platform vendors to address the requirements of workflows sustainably at the exascale.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2018

Decreased Electron Transfer between Cr(VI) and AH 2 DS in the Presence of Goethite

9,10‐Anthraquinone‐2,6‐disulfonic acid (AQDS) is commonly used as a model species to examine the influence of quinones on different biogeochemical cycles. The reduced form of this quinone, AH 2 DS, can donate electrons to the toxic metal species Cr(VI), leading to the precipitation of less soluble Cr(III) phases. Due to the environmental abundance of Fe(III) (oxyhydr)oxides, such as goethite (α‐FeOOH), it is important to study the role of these mineral phases on the electron transfer reaction between AH 2 DS and Cr(VI). In this study, this electron transfer reaction is examined in the presence and absence of goethite at three different ratios of AH 2 DS/Cr(VI). Ultraviolet‐visible spectroscopy is used to qualitatively assess the oxidation state of AQDS during reactions with goethite. Iron K‐edge and Cr K‐edge X‐ray absorption spectroscopy are used to examine the role of goethite in electron transfer and identify Cr(III) phases that form. Goethite inhibits the extent of Cr(VI) reduction to Cr(III), most notably at the highest ratio of AH 2 DS/Cr(VI) investigated. Production of semiquinone radical species may limit electron transfer and decrease the yields of Fe(II) and Cr(III), both in the presence and absence of goethite. Understanding abiotic electron transfer reactions that occur in systems with multiple redox active species is important to determine the contribution of abiotic redox reactions to Fe biogeochemical cycling in natural soils. Core Ideas Goethite inhibits the reduction of Cr(VI) to Cr(III) in the presence of AH 2 DS. Semiquinone radical production probably leads to a decrease in reducing equivalents. X‐ray absorption spectroscopy shows no Fe x Cr x (OH) 3 phases form in Cr(VI) reduction.

Tomaszewski, Elizabeth J.↗

DOE OSTI2024

Mercury’s Chaotic Secular Evolution as a Subdiffusive Process

Abstract Mercury’s orbit can destabilize, generally resulting in a collision with either Venus or the Sun. Chaotic evolution can causeg 1 to decrease to the approximately constant value ofg 5 and create a resonance. Previous work has approximated the variation ing 1 as stochastic diffusion, which leads to a phenomological model that can reproduce the Mercury instability statistics of secular andN-body models on timescales longer than 10 Gyr. Here we show that the diffusive model significantly underpredicts the Mercury instability probability on timescales less than 5 Gyr, the remaining lifespan of the solar system. This is becauseg 1 exhibits larger variations on short timescales than the diffusive model would suggest. To better model the variations on short timescales, we build a new subdiffusive phenomological model forg 1 . Subdiffusion is similar to diffusion but exhibits larger displacements on short timescales and smaller displacements on long timescales. We choose model parameters based on the behavior of theg 1 trajectories in theN-body simulations, leading to a tuned model that can reproduce Mercury instability statistics from 1–40 Gyr. This work motivates fundamental questions in solar system dynamics: why does subdiffusion better approximate the variation ing 1 than standard diffusion? Why is there an upper bound ong 1 , but not a lower bound that would prevent it from reachingg 5 ?

Astronomy & Astrophysics↗

DOE OSTI2018

Influence of temperature on the lattice misfit and elastic moduli of a Ni based single crystal superalloy with high volume fraction of γ′ phase

Highlights: • The variation of the lattice misfit with temperature in a Ni based single-crystal superalloy with high volume fraction of γ' phase was determined by high-temperature X-ray diffraction (HT-XRD) technique at temperatures between 25 °C and 1200 °C. • When the temperature was higher than 1100 °C, the γ' phase obviously dissolved, leading to a lower content of Mo and Re in the γ phase, and then resulted in a smaller absolute value of the lattice misfit. • The contribution of dissolution of γ′ phase to the reduction of the misfit increased with rising temperature and reached 29.5% at 1200 °C. • When the temperature exceeded 1100 °C, the difference of elastic moduli of γ and γ′ phases increased with rising temperature was attributed to the elastic modulus of γ phase decreased significantly. - Abstract: The variation of the lattice parameter with temperature in a Ni based single-crystal superalloy with high volume fraction of γ′ phase IC32 was determined by high-temperature X-ray diffraction (HT-XRD) technique at temperatures between 25 °C and 1200 °C. The effects of the temperature, especially the ultra-high temperature (beyond 1100 °C), on lattice misfit, elastic moduli, γ′ volume fraction and composition of γ, γ′ phases were investigated in this study. The results show that the absolute value of lattice misfit first increased and then decreased with increasing temperature and reached the maximum of 0.53% at 1100 °C. When the temperature was higher than 1100 °C, the γ′ precipitate obviously dissolved, leading to a lower content of Mo and Re in the γ phase, and then resulted in a smaller absolute value of lattice misfit. The contribution of dissolution of γ′ phase to the reduction of the misfit increased with rising temperature and reached 29.5% at 1200 °C. Moreover, when the temperature was above 1100 °C, the elastic moduli of the γ phase and alloy decreased significantly, while this phenomenon was not observed in the γ′ phase.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Tetrahedral Tilting and Lithium‐Ion Transport in Halide Argyrodites Prepared by Rapid, Microwave‐Assisted Synthesis

Abstract This study demonstrates a rapid, dry, microwave‐assisted (MW) synthesis method that enables preparation of halide argyrodites ( , , ) in less than 20 min. The structures and ion transport properties of the resulting materials are compared with those synthesized by conventional solid‐state synthesis methods. The microwave‐assisted method leads to increased site disorder and elevated Arrhenius prefactors (), which lead to an order of magnitude improvement in the 30 ionic conductivity of MW‐. X‐ray pair distribution function analysis (XPDF) reveals significant rotational disorder of the units, which is impacted by the synthesis method, choice of halide, and presence of / site disorder. These rotational displacements are strongly correlated with ion transport, specifically and entropy of migration (). Overall, this study demonstrates a rapid synthesis route for preparing high‐quality halide argyrodite solid‐state electrolytes in less than 20 min, and further unravels atomistic insights into the interplay of structural disorder, rotational dynamics, and ion transport mechanisms.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Enhanced Stability of Li Metal Anodes by Synergetic Control of Nucleation and the Solid Electrolyte Interphase

Use of a protective coating on a lithium (Li) metal anode (LMA) is an effective approach to enhance its coulombic efficiency and cycling stability. Here we report a facile approach to produce uniform silver (Ag) nanoparticle-decorated LMAs for high-performance Li metal batteries (LMBs). This effective treatment can lead to well controlled nucleation and the formation of a stable solid electrolyte interphase (SEI). Ag nanoparticles embedded in the surface of Li anodes induced uniform Li plating/stripping morphologies with reduced overpotential. More importantly, cross-linked lithium fluoride (LiF) networks formed during Ag+ reduction enabled a highly stable SEI layer. Based on the Ag-LiF decorated anodes, LMBs with LiNi1/3Mn1/3Co1/3O2 cathode (~1.8 mAh cm-2) can retain >80% capacity over 500 cycles. The similar results were also obtained when the same approach was applied to the design of stable sodium (Na) anodes. These results indicate that synergetic control of the nucleation and SEI is an efficient approach to stabilize rechargeable metal batteries.

anode↗

DOE OSTI2022

Near‐Room‐Temperature Magnetoelectric Coupling via Spin Crossover in an Iron(II) Complex

Abstract Magnetoelectric coupling is achieved near room temperature in a spin crossover Fe II molecule‐based compound, [Fe(1bpp) 2 ](BF 4 ) 2 . Large atomic displacements resulting from Jahn–Teller distortions induce a change in the molecule dipole moment when switching between high‐spin and low‐spin states leading to a step‐wise change in the electric polarization and dielectric constant. For temperatures in the region of bistability, the changes in magnetic and electrical properties are induced with a remarkably low magnetic field of 3 T. This result represents a successful expansion of magnetoelectric spin crossovers towards ambient conditions. Moreover, the observed 0.3–0.4 mC m −2 changes in the H ‐induced electric polarization suggest that the high strength of the coupling obtained via this route is accessible not just at cryogenic temperatures but also near room temperature, a feature that is especially appealing in the light of practical applications.

Owczarek, Magdalena↗

DOE OSTI2022

Near‐Room‐Temperature Magnetoelectric Coupling via Spin Crossover in an Iron(II) Complex

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Identification of robust microsatellite markers for wild pig fecal DNA

ABSTRACT Collection of fecal samples for use in a genetic capture‐mark‐recapture framework has become popular as a noninvasive method of monitoring wildlife populations. A major caveat to this process, however, is that fecal samples often yield low quality DNA that is prone to genotyping errors, potentially leading to biases in population parameter estimation. Therefore, considerable care is required to identify robust genetic markers, especially in hot or humid conditions that may accelerate DNA degradation. We identified microsatellite loci in wild pig ( Sus scrofa ) fecal samples that were robust and informative within warm, humid ecosystems. To examine how degradation affected genotyping success, we sampled pig feces across 5 days and calculated how the number of quantitative polymerase chain reaction (qPCR) cycles required to reach the fluorescent threshold ( C t ) changed over time. We identified 17 microsatellite loci that had high polymorphism and amplification success and low genotyping error rates (0–0.050 per locus). In the degradation experiment, C t increased over the 5 days, but in the absence of rain, the majority of samples produced accurate genotypes after 5 days (2,211/2,550 genotypes). Based on the high amplification success and low error rates, even after 5 days of exposure to warm, humid conditions, these loci are useful for estimating population parameters in pig fecal samples. © 2016 The Wildlife Society.

Kierepka, Elizabeth M.↗