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NASA NTRSDate not supplied

Hierarchical screening for Li-based solid electrolytes using fast, interpretable machine-learned potentials

Li-based solid-state electrolyte materials enable safer, all-solid-state batteries but the computational search for candidates with favorable stability and Li-ion conductivity is challenging due to the size of the search space and the cost of evaluating transport properties with ab initio methods. The prohibitive cost of high-throughput screening with DFT has lead to the development of surrogate models using geometric analysis, empirical potentials, and descriptors for ionic transport. Here, I will discuss a hierarchical screening approach for identifying promising materials using a combination of density functional theory, bond-valence methods, and machine learning potentials generated with the Ultra-Fast Force Fields (UF3) framework. We show how the inexpensive bond-valence method can be used to guide the generation of training samples for machine learning, in addition to filtering candidates. Finally, we apply the hierarchical workflow to screen for ionic conductivity across a database of Li-containing compounds.

Materials discovery↗

NASA NTRSDate not supplied

Hierarchical Screening for Li-Based Solid Electrolytes Using Fast, Interpretable Machine-Learned Potentials

Materials discovery↗

DOE OSTI2015

Decay Constants $f_B$ and $f_{B_s}$ from HISQ Simulations

We give a progress report on a project aimed at a high-precision calculation of the decay constants $f_B$ and $f_{B_s}$ from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios $m_{ud}/m_s$, including approximately physical sea-quark masses. This range of parameters provides excellent control of the continuum limit and of heavy-quark discretization errors. We present a preliminary error budget with projected uncertainties of 2.2~MeV and 1.5~MeV for $f_B$ and $f_{B_s}$, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

The JLab TMD Program at 6 GeV and 11 GeV

The precise mapping of the nucleon’s transverse momentum dependent parton distributions (TMDs) in the valence quark region has emerged as one of the flagship physics programs of the recently upgraded Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab). The TMDs describe the three-dimensional, spin-correlated densities of quarks and gluons in the nucleon in momentum space, and are accessible experimentally through detailed studies of the Semi-Inclusive Deep Inelastic Scattering (SIDIS) process, N ( e ; e 0 h ) X . The already unrivaled intensity, polarization and duty factor performance of CEBAF will combine with the dramatic expansion of its kinematic reach embodied by the recent near-doubling of the maximum beam energy to enable the first fully differential precision measurements of SIDIS structure functions in the valence region. In this paper, I will review the existing and forthcoming SIDIS results from the 6 GeV era of CEBAF operations and present an overview of the planned JLab SIDIS program at 11 GeV beam energy

Puckett, Andrew J.↗

DOE OSTI2014

Update on a short-distance $D^0$-meson mixing calculation with $N_f=2+1$ flavors

We present an update on our calculation of the short-distance $D^0$-meson mixing hadronic matrix elements. The analysis is performed on the MILC collaboration's $N_f=2+1$ asqtad configurations. We use asqtad light valence quarks and the Sheikoleslami-Wohlert action with the Fermilab interpretation for the valence charm quark. SU(3), partially quenched, rooted, staggered heavy-meson chiral perturbation theory is used to extrapolate to the chiral-continuum limit. Systematic errors arising from the chiral-continuum extrapolation, heavy-quark discretization, and quark-mass uncertainties are folded into the statistical errors from the chiral-continuum fits with methods of Bayesian inference. A preliminary error budget for all five operators is presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Searching for the $X(3872)$ and $Z_c^+(3900)$ on HISQ Lattices

We present preliminary simulation results for the I = 0 charmonium state $X(3872)(1^{++})$ and the I = 1 charmonium state $Z_c^+(3900)(1^{+-})$. The study is performed on gauge field configurations with 2+1+1 flavors of highly improved staggered sea quarks (HISQ) with clover (Fermilab interpretation) charm quarks and HISQ light valence quarks. Since the $X(3872)$ lies very close to the open charm $D \bar D^*$ threshold, we use a combination of $\bar c c$ and $D \bar D^* + \bar D D^*$ interpolating operators. For the $Z_c^+(3900)$ we use a combination of $J/\psi \pi$ and $D \bar D^* + \bar D D^*$ channels. This is the first such study with HISQ sea quarks and light valence quarks. To this end, we describe a variational method for treating staggered quarks that incorporates both oscillating and non-oscillating components.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

$B_s \to K \ell\nu$ Form Factors with 2+1 Flavors

Using the MILC 2+1 flavor asqtad quark action ensembles, we are calculating the form factors $f_0$ and $f_+$ for the semileptonic $B_s \rightarrow K \ell\nu$ decay. A total of six ensembles with lattice spacing from $\approx0.12$ to 0.06 fm are being used. At the coarsest and finest lattice spacings, the light quark mass $m'_l$ is one-tenth the strange quark mass $m'_s$. At the intermediate lattice spacing, the ratio $m'_l/m'_s$ ranges from 0.05 to 0.2. The valence $b$ quark is treated using the Sheikholeslami-Wohlert Wilson-clover action with the Fermilab interpretation. The other valence quarks use the asqtad action. When combined with (future) measurements from the LHCb and Belle II experiments, these calculations will provide an alternate determination of the CKM matrix element $|V_{ub}|$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2019

Stabilized scintillator

A stabilized scintillator includes a compound corresponding to formula (2) or (3), or activated derivatives thereof: A.sub.2BB'.sub.xB''.sub.yX.sub.6 (2) A.sub.2BB'X.sub.xX'.sub.y (3) wherein A and B are monovalent cations, B' is a trivalent cation, X is a halogen, x and y are molar percentages, x+y=1; B'' is an aliovalent exchange cation that has a different valence than B', X' is an aliovalent exchange anion that has a different valence than X. A method of preparing the stabilized scintillator is also disclosed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Hard x-ray standing-wave photoemission study of the interfaces in a BiFeO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ superlattice

Hybrid multiferroics such as BiFeO$_3$ (BFO) and La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO) heterostructures are highly interesting functional systems due to their complex electronic and magnetic properties. One of the key parameters influencing the emergent properties is the quality of interfaces, where varying interdiffusion lengths can give rise to different chemistry and distinctive electronic states. Here we report high-resolution depth resolved chemical and electronic investigation of BFO/LSMO superlattice using standing-wave hard X-ray photoemission spectroscopy in the first-order Bragg as well as near-total-reflection geometry. Our results show that the interfaces of BFO on top of LSMO are atomically abrupt, while the LSMO on top of BFO interfaces show an interdiffusion length of around 1.2 unit cells. The two interfaces also exhibit different chemical gradients, with the BFO/LSMO interface being Sr-terminated by a spectroscopically distinctive high binding energy component in Sr 2p core-level spectra, which is spatially contained within 1 unit cell from the interface. From the electronic point of view, unique valence band features were observed for bulk-BFO, bulk-LSMO and their interfaces. Our X-ray optical analysis revealed a unique electronic signature at the BFO/LSMO interface, which we attribute to the coupling between those respective layers. Valence band decomposition based on the Bragg-reflection standing-wave measurement also revealed the band alignment between BFO and LSMO layers. Our work demonstrates that standing-wave hard x-ray photoemission is a reliable non-destructive technique for probing depth-resolved electronic structure of buried layers and interfaces with sub-unit-cell resolution. Equivalent investigations can be successfully applied to a broad class of material such as perovskite complex oxides with emergent interfacial phenomena.

Martins, HP↗

DOE OSTI2020

Neutral Pion Electroproduction and development of a Neutral Particle Spectrometer

Protons and neutrons, i.e. nucleons, are the basic building blocks of the matter in the visible universe. The strong force binds the nucleons to form nuclei. The electromagnetic force forms the atoms by binding the electrons with the nuclei. The electromagnetic interaction is well understood by Quantum Electrodynamics (QED), which shows the most precise predictability amongst all the theories in physics. In QED, charges interact with each other by exchanging photons. The Quantum Chromodynamics (QCD) describes the strong interaction. Its degrees of freedom are quarks and gluons, the fundamental constituents of the nucleons. The quarks interact with each other by exchanging gluons. However, unlike QED, the gluons interact amongst themselves. This feature of self bindings of the gluons confines the quarks and gluons in the nucleons/hadrons, never to be seen as free. In order to study some of the features of QCD, such as confinement or the structure of the nucleon, one usually needs to rely on experiments. Electromagnetic probes, governed by the well-understood QED, are excellent tools to probe the nucleon. In general, different scales, e.g. electron beam energies, probe different regions of the nucleon. At low energy, of the order of a few GeV, the electron probes the nucleon in the valence quark region. As its energy increases, the electron probes the sea quark and gluon regions. The study of the nucleon structure in all these regions is needed to fully understand QCD. Form factors and parton distribution functions measured from elastic scattering and deep inelastic scattering of leptons off nucleons have provided a partial view of the internal structure of the nucleon. In the mid-1990s, Generalized Parton Distributions (GPDs) were developed. These new objects are a generalization of the form factors and parton distribution functions, but contain richer information on the nucleon internal structure. GPDs are accessible experimentally by deep exclusive reactions. Deeply virtual Compton scattering (DVCS) and deeply virtual meson production (DVMP) are some examples. The first dedicated DVCS/DVMP experiment took place in 2004 in Hall A at The Thomas Jefferson National Accelerator Facility, i.e. Jefferson Lab, in Virginia, U.S.A. A new DVCS/DVMP experiment, after the beam energy upgrade of Jefferson Lab, was carried out in Hall A in a wider kinematic range. Its data were taken from 2014 to 2016. In Hall C at Jefferson Lab, the next DVCS/DVMP experiment will take place. The Hall C experiment will further exploit the kinematic range with higher precision. A Neutral Particle Spectrometer (NPS) is in development to measure DVCS/DVMP events under high background conditions. Jefferson Lab will provide the highest precision data in the valence quark region for various exclusive reactions. The Electron-Ion Collider (EIC) is a future experimental facility currently planned to start operations around 2030 in the U.S.A. Its high energy and high luminosity will probe the sea quark and gluon regions providing answers to the outstanding questions of QCD, in particular in the region where matter is dominated by gluons. First of all, this document describes the data analysis and results of the Hall A neutral pion electroproduction off the proton, from the data taken in 2014-2016. Later, some of the developments towards the construction of the electromagnetic calorimeter of the NPS for the upcoming DVCS/DVMP experiment in Hall C are presented. Finally, one of the candidate materials for the EIC calorimeter, a glass scintillator, will be briefly introduced. I have participated to all these projects, in collaboration with many colleagues. I present in this thesis my contributions to each of these projects. My contributions to the neutral pion data analysis were focused on background subtractions on the calorimeter, acceptance calculations, and the estimation of the systematic uncertainty associated to the event selection cuts. Some necessary information on calibrations of the detectors and data analysis methods are also described. In the NPS project, I performed background dose calculations and energy and position resolution studies of the calorimeter, all using Monte Carlo simulations, with realistic geometries of the experimental apparatus. Characterization of the crystals of the calorimeter was also done. Additionally, I measured the radiation hardness of some glass scintillator in its early stage of development. In order to have a future reference when the glass calorimeter prototype will be tested, I simulated the energy resolution of the prototype.

Ko, Ho-San↗

DOE OSTI2013

Probing sea quarks and gluons: the Electron-Ion Collider project

The 21st century holds great promise for reaching a new era for unlocking the mysteries of the structure of the atomic nucleus and the nucleons inside it governed by the theory of strong interactions (QCD). In particular, much remains to be learned about the dynamical basis of the structure of hadrons and nuclei in terms of the fundamental quarks and gluons. One of the main goals of existing and nearly completed facilities is to map out the spin flavor structure of the nucleons in the valence region. A future Electron-Ion Collider (EIC) would be the world's first polarized electron-proton collider, and the world's first e-A collider, and would seek the QCD foundation of nucleons and nuclei in terms of the sea quarks and gluons, matching to these valence quark studies. The EIC will provide a versatile range of kinematics and beam polarization, as well as beam species, to allow for mapping the spin and spatial structure of the quark sea and gluons, to discover the collective effects of gluons in atomic nuclei, and to understand the emergence of hadronic matter from color charge. I will summarize the physics goals and present an overview of the proposed EIC.

Horn, Tanja↗

DOE OSTI2018

Depleted Uranium Discrimination Using Spectral Ratios from Data-Starved Spectra - 18619

The Institute for Clean Energy Technology (ICET) has developed mobile surveying platforms for the retrieval of fired depleted uranium (DU) munitions. ICET surveying platforms are fitted with differential global positioning system (GPS), scintillation detectors, and central processing units (CPUs). The surveying technology has historically been used to assist facilities where DU contamination is a concern to locate, retrieve, and remediate DU-contaminated areas. Residence times over DU sources for mobile systems normally do not produce enough data to use gamma ray spectroscopy to verify the source type. Discussed is a potential method used to discriminate DU signatures in data-starved gamma ray spectral data collected during field surveys. Laboratory tests have shown that data-starved gamma ray spectra for zero-valence, oxide, and uranium ores can be distinguished from each other and from background by spectral ratioing. Zero-valence DU and DU oxide gamma ray signatures differ due to the attenuation of low-energy gammas emitted from U-238 daughters. DU signatures can be differentiated from naturally occurring uranium spectra due to the presence of daughters below U-234, primarily bismuth (Bi)-214, in the uranium decay series. Three primary regions of interest (ROI) within the analyzed test spectra are used to roughly characterize the shape of each test spectrum and compare them to background. The three ROIs are focused around the gamma-emitting daughters of U-238: thorium (Th)-234, protactinium (Pa)-234 metastable (m), and Bi-214. One of the three regions is considered the base region. This region is used to estimate what the counts in the other two regions should be by multiplying the counts in the ROIs by a ratio of background counts from an area previously found to be impacted. Using this spectral ratioing technique, a non-zero difference in spectral ratio values indicates a shift in the test spectra away from background. Calculating ratios between the base region and the other two regions allows for a graphical representation of the data in a two-dimensional spectral ratioing space, which is used to differentiate between the types of uranium sources previously mentioned. Surveying processes that are based on gross counts from scintillation counters can result in a large number of false positives as a result of shifting background signals or the presence of naturally occurring uranium. Application of the spectral ratioing technique can further assist in site characterization by analyzing all of the data-starved survey spectra to identify false positives or the need for additional data collection. Accurate surveys of DU testing and training ranges reduces the costs associated with range clean-up by discriminating clean areas from those requiring remediation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

High-spin Fe 2+ and Fe 3+ in single-crystal aluminous bridgmanite in the lower mantle

In this work, spin and valence states of iron in single-crystal bridgmanite (Mg 0.89 Fe 0.12 Al 0.11 Si 0.89 O 3 ) are investigated using X-ray emission and Mössbauer spectroscopies with laser annealing up to 115 GPa. The results show that Fe predominantly substitutes for Mg 2+ in the pseudo-dodecahedral A site, in which 80% of the iron is Fe 3+ that enters the lattice via the charge-coupled substitution with Al 3+ in the octahedral B site. The total spin momentum and hyperfine parameters indicate that these ions remain in the high-spin state with Fe 2+ having extremely high quadrupole splitting due to lattice distortion. (Al,Fe)-bearing bridgmanite is expected to contain mostly high-spin, A-site Fe 3+ , together with a smaller amount of A-site Fe 2+ , that remains stable throughout the region. Even though the spin transition of B-site Fe 3+ in bridgmanite was reported to cause changes in its elasticity at high pressures, (Fe,Al)-bearing bridgmanite with predominantly A-site Fe will not exhibit elastic anomalies associated with the spin transition.

58 GEOSCIENCES↗

DOE OSTI2021

Zero-Valent Palladium Single-Atoms Catalysts Confined in Black Phosphorus for Efficient Semi-Hydrogenation

Single-atom catalysts (SACs) represent a new frontier in heterogeneous catalysis due to their remarkable catalytic properties and maximized atomic utilization. However, single atoms often bond to the support with polarized electron density and thus exhibit a high valence state, limiting their catalytic scopes in many chemical transformations. In this study, it is demonstrated that 2D black phosphorus (BP) acts as giant phosphorus (P) ligand to confine a high density of single atoms (e.g., Pd 1 , Pt 1 ) via atomic layer deposition. Unlike other 2D materials, BP with relatively low electronegativity and buckled structure favors the strong confinement of robust zero-valent palladium SACs in the vacancy site. Metallic Pd 1 /BP SAC shows a highly selective semi-hydrogenation of phenylacetylene toward styrene, distinct from metallic Pd nanoparticles that facilitate the formation of fully hydrogenated products. Density functional theory calculations reveal that Pd atom forms covalent-like bonding with adjacent P atoms, wherein H atoms tend to adsorb, aiding the dissociative adsorption of H 2 . Zero-valent Pd in the confined space favors a larger energy gain for the synthesis of partially hydrogenated product over the fully hydrogenated one. This work provides a new route toward the synthesis of zero-valent SACs on BP for organic transformations.

36 MATERIALS SCIENCE↗

DOE OSTI2018

First-Principles Investigation of Equiatomic Quaternary Heusler Alloys NbVMnAl and NbFeCrAl and a Discussion of the Generalized Electron-Filling Rule

Plane-wave pseudo-potential methods based on density functional theory are used to study the electronic structures, magnetic, and half-metallic properties of the equiatomic quaternary Heusler alloys NbVMnAl and NbFeCrAl. Calculated results reveal that NbVMnAl and NbFeCrAl alloys are newly designed half-metallic ferrimagnets with a total magnetic moment (M{sub t}) of 2 μ{sub B}. We found that the Slater-Pauling rule, i.e., the relationship between the M{sub t} and the total number of valence electrons (Z{sub t}) of these two alloys was different. For NbVMnAl alloy, it obeys the M{sub t} = |Z{sub t} − 18| rule. For NbFeCrAl, it satisfies the M{sub t} = |Z{sub t} − 24| rule. Also, we observed that the half-metallic band gap (HM-BG) of these two alloys was different. Namely, for one material (NbFeCrAl), it is located in the spin-up channel, and in the other (NbVMnAl), it is located in the spin-down channel. To explain these phenomena, in this work, the generalized electron-filling rule was investigated, and the origin of the HM-BG of NbVMnAl and NbFeCrAl was studied. We hope that our work may provide theoretical guidance in searching for Nb-based equiatomic quaternary Heusler half-metals in the future.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Synthesis and Magnetic Properties of Nanocrystalline FeTiO{sub 3} Materials

Ilmenite (FeTiO{sub 3}) nanoparticles with different size distributions were prepared through a sol-gel auto-ignition method. As-prepared powder is annealed at moderate temperatures to get nanocrystalline FeTiO{sub 3}, and structural, micro-structural, and magnetization characterizations are carried out. Magnetization vs temperature shows antiferromagnetic ordering around 52 K and below 15 K a weak ferromagnetic order develops. The Curie-Weiss law is well obeyed above the Néel temperature (T{sub N}) for all samples. Hysteresis curves show finite coercivity below the peak temperature and none at room temperature. M-H curves for all the samples cooled with a bias magnetic field show exchange bias below T{sub N} which is interpreted due to the finite size and surface effects. The exchange bias is attributed to weak ferromagnetism due to surface spin disorder (Dzyaloshinskii-Moriya interaction) and ferromagnetic interaction (double exchange) due to mixed valence states of Fe ions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

New Quaternary Half-Metallic Materials of the Z{sub t} − 28 Rule in LiMgPdSn-Type Heusler Alloys

This paper presents first-principles calculations with the full-potential linearized augmented plane-wave method to study a series of LiMgPdSn-type Heusler alloys. The chemical formula is XX{sup ′}YZ, where X = Fe, Co, or Ni; X{sup ′} = Mn; Y = Cu or Zn; and Z = Si, Al, Ga, or Ge. Eight compounds are found to be half-metallic magnets and obey the Slater–Pauling rule with the total number of valence electrons (Z{sub t}) of 28. The half-metallic band gap in CoMnZnSi compounds reaches its maximum of 0.66 eV. CoMnCuGe and CoMnZnGa can be transformed from a quasi-half-metallic alloy to a half-metallic alloy by employing sufficient compression stress.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Proximity Effect of Magnesium Diboride on Single-Walled Carbon Nanotube: an Ab Initio Study

Magnesium diboride (MgB{sub 2}) superconductor with excellent physical properties continues to attract the attention of researchers since its discovery. It derives its versatility from the absence of weak links, large coherence length, and small anisotropy. On the other hand, reports of superconductivity in small-diameter single-walled carbon nanotubes (SWCNTs) suspended between superconducting contacts and proximity induced supercurrents in Ta/SWNTs/Au junctions have also aroused great interest in the scientific community. Proximity induced superconductivity in SWCNTs has opened up new frontiers of research which will lead to many novel discoveries. This paper reports ab initio investigations on the proximity effect of MgB{sub 2} on the electronic structure of a SWCNT. Condensation of electronic states is observed in the electronic band structure of the pristine SWCNT when MgB{sub 2} is held in proximity. An additional band gap is generated below the lowest energy state of the valence band of the pristine CNT which we suggest, is due to Cooper pair formation. This leads to the prediction that SWCNTs will show superconducting properties in proximity of MgB{sub 2}. We envision MgB{sub 2}-coated SWCNTs as a novel nanomaterial that has a combination of proximity induced superconductivity and inherently unique mechanical and optical properties of SWCNTs.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗