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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on DyHoTl2 by Materials Project

HoDyTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ho is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Ho–Tl bond lengths are 3.28 Å. Dy is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Dy–Tl bond lengths are 3.28 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Ho and four equivalent Dy atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Tl by Materials Project

Mg3Tl is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to eight equivalent Mg and four equivalent Tl atoms to form distorted MgMg8Tl4 cuboctahedra that share corners with four equivalent MgMg8Tl4 cuboctahedra, corners with eight equivalent TlMg12 cuboctahedra, edges with twenty-four MgMg8Tl4 cuboctahedra, faces with six equivalent TlMg12 cuboctahedra, and faces with twelve MgMg8Tl4 cuboctahedra. All Mg–Mg bond lengths are 3.22 Å. All Mg–Tl bond lengths are 3.18 Å. In the second Mg site, Mg is bonded to eight Mg and four equivalent Tl atoms to form MgMg8Tl4 cuboctahedra that share corners with twelve equivalent MgMg8Tl4 cuboctahedra, edges with eight equivalent TlMg12 cuboctahedra, edges with sixteen MgMg8Tl4 cuboctahedra, faces with four equivalent TlMg12 cuboctahedra, and faces with fourteen MgMg8Tl4 cuboctahedra. All Mg–Mg bond lengths are 3.18 Å. All Mg–Tl bond lengths are 3.22 Å. Tl is bonded to twelve Mg atoms to form TlMg12 cuboctahedra that share corners with four equivalent TlMg12 cuboctahedra, corners with eight equivalent MgMg8Tl4 cuboctahedra, edges with eight equivalent TlMg12 cuboctahedra, edges with sixteen equivalent MgMg8Tl4 cuboctahedra, faces with four equivalent TlMg12 cuboctahedra, and faces with fourteen MgMg8Tl4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrHoTl2 by Materials Project

HoPrTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ho is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Ho–Tl bond lengths are 3.34 Å. Pr is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Pr–Tl bond lengths are 3.34 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Ho and four equivalent Pr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmErTl2 by Materials Project

ErPmTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Er is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Er–Tl bond lengths are 3.32 Å. Pm is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Pm–Tl bond lengths are 3.32 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Er and four equivalent Pm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeSmTl2 by Materials Project

SmCeTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Sm is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Sm–Tl bond lengths are 3.35 Å. Ce is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Ce–Tl bond lengths are 3.35 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Sm and four equivalent Ce atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl2CdBi by Materials Project

CdTl2Bi crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two CdTl2Bi ribbons oriented in the (1, 0, 0) direction. Cd is bonded in a linear geometry to two equivalent Tl atoms. Both Cd–Tl bond lengths are 2.97 Å. Tl is bonded in a linear geometry to one Cd and one Bi atom. The Tl–Bi bond length is 2.81 Å. Bi is bonded in a linear geometry to two equivalent Tl atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrEuTl2 by Materials Project

SrEuTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Sr is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Sr–Tl bond lengths are 3.53 Å. Eu is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Eu–Tl bond lengths are 3.53 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Sr and four equivalent Eu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsTlCl3 by Materials Project

CsTlCl3 is (Cubic) Perovskite structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. Cs is bonded to twelve Cl atoms to form CsCl12 cuboctahedra that share corners with twelve equivalent CsCl12 cuboctahedra, faces with six equivalent CsCl12 cuboctahedra, and faces with eight equivalent TlCl6 octahedra. There are a spread of Cs–Cl bond distances ranging from 3.89–4.00 Å. Tl is bonded to six Cl atoms to form TlCl6 octahedra that share corners with six equivalent TlCl6 octahedra and faces with eight equivalent CsCl12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–2°. All Tl–Cl bond lengths are 2.79 Å. There are three inequivalent Cl sites. In the first Cl site, Cl is bonded to four equivalent Cs and two equivalent Tl atoms to form a mixture of distorted edge, face, and corner-sharing ClCs4Tl2 octahedra. The corner-sharing octahedra tilt angles range from 1–61°. In the second Cl site, Cl is bonded to four equivalent Cs and two equivalent Tl atoms to form a mixture of distorted edge, face, and corner-sharing ClCs4Tl2 octahedra. The corner-sharing octahedra tilt angles range from 1–61°. In the third Cl site, Cl is bonded to four equivalent Cs and two equivalent Tl atoms to form a mixture of distorted edge, face, and corner-sharing ClCs4Tl2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on DyLuTl2 by Materials Project

LuDyTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Lu is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Lu–Tl bond lengths are 3.26 Å. Dy is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Dy–Tl bond lengths are 3.26 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Lu and four equivalent Dy atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaTl2Pt by Materials Project

NaPtTl2 crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two NaPtTl2 ribbons oriented in the (1, 0, 0) direction. Na is bonded in a linear geometry to two equivalent Tl atoms. Both Na–Tl bond lengths are 3.16 Å. Pt is bonded in a linear geometry to two equivalent Tl atoms. Both Pt–Tl bond lengths are 2.60 Å. Tl is bonded in a linear geometry to one Na and one Pt atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ScTiTl2 by Materials Project

ScTiTl2 crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two ScTiTl2 ribbons oriented in the (1, 0, 0) direction. Sc is bonded in a linear geometry to two equivalent Tl atoms. Both Sc–Tl bond lengths are 2.90 Å. Ti is bonded in a linear geometry to two equivalent Tl atoms. Both Ti–Tl bond lengths are 2.82 Å. Tl is bonded in a linear geometry to one Sc and one Ti atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Spin‐Orbit Effects in a Thallium Borohydride Stabilized by Coordination to Bis(diisopropylamino)Cyclopropenylidene (BAC)

The reaction of Tl(OTf) with 2 equiv of bis(diisopropylamino)cyclopropenylidene (BAC) in THF results in formation of [Tl(BAC) 2 (OTf)] (1) in moderate yields. Subsequent reaction of 1 with [K][H 2 -9-BBN] ([H 2 -9-BBN] − = dihydrido 9-boratabicyclo[3.3.1]nonane) in THF results in formation of [Tl(BAC)(μ-H 2 -9-BBN)] 2 (3), also in moderate yield. Complex 3 is the first reported thallium borohydride. We attribute its thermal stability to the strong donor ability of the BAC co-ligand. Both 1 and 3 exhibit trigonal pyramidal geometries about Tl + in the solid-state, indicative of the presence of stereochemically active lone pairs. The hydride environment in 3 is calculated to exhibit a 3.9 ppm downfield shift attributed to spin-orbit effects from the adjacent Tl center.

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

Cross-functional transferability in foundation machine learning interatomic potentials

The rapid development of foundation potentials (FPs) in machine learning interatomic potentials demonstrates the possibility for generalizable learning of the universal potential energy surface. The accuracy of FPs can be further improved by bridging the model from lower-fidelity datasets to high-fidelity ones. In this work, we analyze the challenge of this transfer learning (TL) problem within the CHGNet framework. We show that significant energy scale shifts and poor correlations between GGA and r 2 SCAN hinder cross-functional transferability. By benchmarking different TL approaches on the MP-r 2 SCAN dataset, we demonstrate the importance of elemental energy referencing in the TL of FPs. By comparing the scaling law with and without the pre-training on a low-fidelity dataset, we show that significant data efficiency can still be achieved through TL, even with a target dataset of sub-million structures. We highlight the importance of proper TL and multi-fidelity learning in creating next-generation FPs on high-fidelity data.

Huang, Xu [University of California, Berkeley, CA ↗
DOE OSTI2024

ITER ECH Transmission Line System Design and Status

The electron cyclotron (EC) heating & current drive (H&CD) system on ITER provides plasma heating by generating, transmitting, and launching high-intensity, high-frequency (170 GHz) electromagnetic wave energy steerable across the plasma cross-section. The transmission line (TL) subsystem connects the Matching Optics Unit (MOU) on each of the 24 gyrotrons to the 32 feed points in the four upper launchers and the 24 feed points in the equatorial launcher. Each TL must be able to operate at up to 1.2 MW of input power for up to 1 hour pulse lengths. The TL system contains 50 mm water-cooled corrugated waveguide, 90o miter bends, 140o miter bends, polarizer miter bend pairs, switches, expansion units, pumpouts, DC breaks, MOU-TL adapters, Radio Frequency (RF) loads, and isolation shutter valves. A detailed finite element analysis has been used to verify the thermo-mechanical performance of each component. The microwave performance has been analyzed using a 2-D electromagnetic code combined with a Monte Carlo code. This approach allows the impact of manufacturing and installation tolerances to be assessed and optimized to provide a high probability of achieving the system performance requirements. Prototypes of the waveguide and TL components have been fabricated and tested at high-power. Production contracts are now being issued for fabrication and delivery of the waveguide and components to ITER.

Hanson, Gregory↗
DOE OSTI2022

First-Principles Calculations of Thermoelectric Transport Properties of Quaternary and Ternary Bulk Chalcogenide Crystals

Chalcogenide crystals have a wide range of applications, especially as thermoelectric materials for energy conversion. Thermoelectric materials can be used to generate an electric current from a temperature gradient based on the Seebeck effect and based on the Peltier effect, and they can be used in cooling applications. Using first-principles calculations and semiclassical Boltzmann theory, we have computed the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, power factor, and figure of merit of 30 chalcogenide crystals. A Quantum Espresso package is used to calculate the electronic properties and locate the Fermi level. The transport properties are then calculated using the BoltzTraP code. The 30 crystals are divided into two groups. The first group has four crystals with quaternary composition (A 2 BCQ 4 ) (A = Tl; B = Cd, Hg; C = Si, Ge, Sn; Q = S, Se, Te). The second group contains 26 crystals with the ternary composition (A’B’Q 2 ) (A’ = Ag, Cu, Au, Na; B’ = B, Al, Ga, In; Q = S, Se, Te). Among these 30 chalcogenide crystals, the results for 11 crystals: Tl 2 CdGeSe 4 , Tl 2 CdSnSe 4 , Tl 2 HgSiSe 4 , Tl 2 HgSnS 4 , AuBSe 2 , AuBTe 2 , AuAlTe 2 , AuGaTe 2 , AuInTe 2 , AgAlSe 2 , and AgAlTe 2 are revealed for the first time. In addition, temperature-dependent transport properties of pure and doped AgSbSe 2 and AgSbTe 2 crystals with dopant compositions of AgSb 0.94 Cd 0.06 Te 2 and AgSbTe 1.85 Se 0.15 were explored. These results provide an excellent database for bulk chalcogenides crucial for a wide range of potential applications in renewable energy fields.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Development of the tangent linear and adjoint models of the global online chemical transport model MPAS-CO 2 v7.3

We describe the development of the tangent linear (TL) and adjoint models of the Model for Prediction Across Scales (MPAS)-CO 2 transport model, which is a global online chemical transport model developed upon the non-hydrostatic Model for Prediction Across Scales – Atmosphere (MPAS-A). The primary goal is to make the model system a valuable research tool for investigating atmospheric carbon transport and inverse modeling. First, we develop the TL code, encompassing all CO 2 transport processes within the MPAS-CO 2 forward model. Then, we construct the adjoint model using a combined strategy involving re-calculation and storage of the essential meteorological variables needed for CO 2 transport. This strategy allows the adjoint model to undertake a long-period integration with moderate memory demands. To ensure accuracy, the TL and adjoint models undergo vigorous verifications through a series of standard tests. The adjoint model, through backward-in-time integration, calculates the sensitivity of atmospheric CO 2 observations to surface CO 2 fluxes and the initial atmospheric CO 2 mixing ratio. To demonstrate the utility of the newly developed adjoint model, we conduct simulations for two types of atmospheric CO 2 observations, namely the tower-based in situ CO 2 mixing ratio and satellite-derived column-averaged CO 2 mixing ratio (X CO 2 ). A comparison between the sensitivity to surface flux calculated by the MPAS-CO 2 adjoint model with its counterpart from CarbonTracker–Lagrange (CT-L) reveals a spatial agreement but notable magnitude differences. These differences, particularly evident for X CO 2 , might be attributed to the two model systems' differences in the simulation configuration, spatial resolution, and treatment of vertical mixing processes. Moreover, this comparison highlights the substantial loss of information in the atmospheric CO 2 observations due to CT-L's spatial domain limitation. Furthermore, the adjoint sensitivity analysis demonstrates that the sensitivities to both surface flux and initial CO 2 conditions spread out throughout the entire Northern Hemisphere within a month. MPAS-CO 2 forward, TL, and adjoint models stand out for their calculation efficiency and variable-resolution capability, making them competitive in computational cost. In conclusion, the successful development of the MPAS-CO 2 TL and adjoint models, and their integration into the MPAS-CO 2 system, establish the possibility of using MPAS's unique features in atmospheric CO 2 transport sensitivity studies and in inverse modeling with advanced methods such as variational data assimilation.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

Solar flare proton spectrum averaged over the last 5000 years

The solar flare differential energy spectrum and integral proton flux above 10 MeV averaged over the last several thousand years are derived from thermoluminescence (TL) data. The dose-rate depth profile is obtained using a new TL equilibrium technique which is independent of the TL decay kinetics. The dose-rate depth profile produced by solar flare protons with a differential energy spectrum of the form dJ/dE = KE to the minus gamma power is calculated for arbitrary gamma. The best fit to the TL data in rock 14310 is obtained for gamma = 2.3 plus or minus 0.2 and an omnidirectional (4 pi) integral flux above 10 MeV of 40 to 80 prot/sq cm/sec. The TL half-life is determined to be 2000 yr. These results are compared to those for Na-22 (half-life of. 2.6 yr) and Al-26 (half-life of 740,000 yr) obtained by Wahlen et al. (1972) and Rancitelli et al. (1972), and it is concluded that the spectral shape and flux of protons in the interval from 25 to 100 MeV is the same within experimental errors when averaged over these three very different time periods.

Hoyt, H. P., Jr.↗
NASA NTRS1976

Effect of air flow, panel curvature, and internal pressurization on field-incidence transmission loss

In the context of sound transmission through aircraft fuselage panels, equations for the field-incidence transmission loss (TL) of a single-walled panel are derived that include the effects of external air flow, panel curvature, and internal fuselage pressurization. Flow is shown to provide a modest increase in TL that is uniform with frequency up to the critical frequency. The increase is about 2 dB at Mach number M = 0.5, and about 3.5 dB at M = 1. Above the critical frequency where TL is damping controlled, the increase can be slightly larger at certain frequencies. Curvature is found to stiffen the panel, thereby increasing the TL at low frequencies, but also to introduce a dip at the 'ring frequency' of a full cylinder having the same radius as the panel. Pressurization appears to produce a slight decrease in TL throughout the frequency range, and also slightly shifts the dips at the critical frequency and at the ring frequency.

Koval, L. R.↗