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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Structural, electronic, and magnetic properties of nearly ideal J eff = 1/2 iridium halides

Heavy transition metal magnets with J e f f = 1 2 electronic ground states have attracted recent interest due to their penchant for hosting new classes of quantum spin liquids and superconductors. Unfortunately, model systems with ideal J e f f = 1 2 states are scarce due to the importance of noncubic local distortions in most candidate materials. In this work, we identify a family of iridium halide systems [i.e., K 2 Ir Cl 6 , K 2 Ir Br 6 , ( NH 4 ) 2 Ir Cl 6 , and Na 2 Ir Cl 6 · 6 ( H 2 O ) ] with Ir 4 + electronic ground states exhibiting extremely small deviations from the ideal J e f f = 1 2 limit. We also find ordered magnetic ground states for the three anhydrous systems, with single-crystal neutron diffraction on K 2 Ir Br 6 revealing type-I antiferromagnetism. This spin configuration is consistent with expectations for significant Kitaev exchange in a face-centered-cubic magnet. This work establishes that incorporating isolated Ir X 6 octahedra in materials, where X is a halogen ion with a low electronegativity, is an effective design principle for realizing unprecedented proximity to the pure J e f f = 1 2 state. However, at the same time, we highlight undeniable deviations from this ideal state, even in clean materials with ideal Ir X 6 octahedra as inferred from the global cubic crystal structures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Design concept for a second interaction region for the Electron-Ion Collider

In addition to the day-one primary Interaction Region (IR), the design of the Electron Ion Collider (EIC) must support operation of a 2nd IR potentially added later. The 2nd IR is envisioned in an existing experimental hall at RHIC IP8, compatible with the same beam energy combinations as the 1st IR over the full center of mass energy range of ~20 GeV to ~140 GeV. The 2nd IR is designed to be complementary to the 1st IR. In particular, a secondary focus is added in the forward ion direction of the 2nd IR hadron beamline to optimize its capability in detecting particles with magnetic rigidities close to those of the ion beam. We provide the current design status of the 2nd IR in terms of parameters, magnet layout and beam dynamics.

Gamage, B. R.↗
DOE OSTI2024

STATUS OF THE SECOND INTERACTION REGION DESIGN FOR ELECTRON-ION COLLIDER

Provisions are being made in the Electron Ion Collider (EIC) design for future installation of a second Interaction Region (IR), in addition to the day-one primary IR. The envisioned location for the second IR is the existing experi- mental hall at RHIC IP8. It is designed to work with the same beam energy combinations as the first IR, covering a full range of the center-of-mass energy of ?20 GeV to ?140 GeV. The goal of the second IR is to complement the first IR, and to improve the detection of scattered particles with magnetic rigidities similar to those of the ion beam. To achieve this, the second IR hadron beamline features a secondary focus in the forward ion direction. The design of the second IR is still evolving. This paper reports the current status of its pa- rameters, magnet layout, and beam dynamics and discusses the ongoing improvements being made to ensure its optimal performance.

Gamage, B.↗
DOE OSTI2024

STATUS OF THE SECOND INTERACTION REGION DESIGN FOR ELECTRON-ION COLLIDER

Provisions are being made in the Electron Ion Collider (EIC) design for future installation of a second Interaction Region (IR), in addition to the day-one primary IR. The envisioned location for the second IR is the existing experi- mental hall at RHIC IP8. It is designed to work with the same beam energy combinations as the first IR, covering a full range of the center-of-mass energy of ?20 GeV to ?140 GeV. The goal of the second IR is to complement the first IR, and to improve the detection of scattered particles with magnetic rigidities similar to those of the ion beam. To achieve this, the second IR hadron beamline features a secondary focus in the forward ion direction. The design of the second IR is still evolving. This paper reports the current status of its pa- rameters, magnet layout, and beam dynamics and discusses the ongoing improvements being made to ensure its optimal performance.

Gamage, B.↗
DOE OSTI2020

Debris Disk Results from the Gemini Planet Imager Exoplanet Survey's Polarimetric Imaging Campaign

We report the results of a ∼4 yr direct imaging survey of 104 stars to resolve and characterize circumstellar debris disks in scattered light as part of the Gemini Planet Imager (GPI) Exoplanet Survey. We targeted nearby (≲150 pc), young (≲500 Myr) stars with high infrared (IR) excesses (L {sub IR}/L {sub ⋆} > 10{sup −5}), including 38 with previously resolved disks. Observations were made using the GPI high-contrast integral field spectrograph in H-band (1.6 μm) coronagraphic polarimetry mode to measure both polarized and total intensities. We resolved 26 debris disks and 3 protoplanetary/transitional disks. Seven debris disks were resolved in scattered light for the first time, including newly presented HD 117214 and HD 156623, and we quantified basic morphologies of five of them using radiative transfer models. All of our detected debris disks except HD 156623 have dust-poor inner holes, and their scattered-light radii are generally larger than corresponding radii measured from resolved thermal emission and those inferred from spectral energy distributions. To assess sensitivity, we report contrasts and consider causes of nondetections. Detections were strongly correlated with high IR excess and high inclination, although polarimetry outperformed total intensity angular differential imaging for detecting low-inclination disks (≲70°). Based on postsurvey statistics, we improved upon our presurvey target prioritization metric predicting polarimetric disk detectability. We also examined scattered-light disks in the contexts of gas, far-IR, and millimeter detections. Comparing H-band and ALMA fluxes for two disks revealed tentative evidence for differing grain properties. Finally, we found no preference for debris disks to be detected in scattered light if wide-separation substellar companions were present.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Infrared Galaxies Detected by the Atacama Cosmology Telescope

We report on 167 infrared (IR) galaxies selected by AKARI and IRAS and detected in the Atacama Cosmology Telescope (ACT) Data Release 5 (DR5) sky maps at the 98, 150, and 220 GHz frequency bands. Of these detections, 134 (80%) of the millimeter counterparts are first-time identifications with ACT. We expand the previous ACT extragalactic source catalogs, by including new 98 GHz detections and measurements from ACT DR5. We also report flux density measurements at the 98, 150, and 220 GHz frequency bands. We compute α 98-150 , α 98-220 , and α 150-220 millimeter-wave spectral indices and far-IR to millimeter-wave spectral indices between 90 μm and 98, 150, and 220 GHz. We specify the galaxy type, based on α 150-220 . We combine publicly available multiwavelength data—including ultraviolet, optical, near-IR, mid-IR, far-IR, and the millimeter measurements obtained in this work—and perform spectral energy distribution (SED) fitting with CIGALE. With the radio emission decomposition advantage of CIGALE V2022.0, we identify the origins of the millimeter emissions for 69 galaxies in our sample. Our analysis also shows that millimeter data alone indicates the need for a radio synchrotron component in the SEDs that are produced by active galactic nuclei (AGNs) and/or star formation. We present SEDs and measured physical properties of these galaxies, such as the dust luminosity, AGN luminosity, the total IR luminosity, and the ratio of the IR and radio luminosity. We quantify the relationships between the total IR luminosity and the millimeter-band luminosities, which can be used in the absence of SED analysis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Can Large Language Models Understand Intermediate Representations?

Intermediate Representations (IRs) are essential in compiler design and program analysis, yet their comprehension by Large Language Models (LLMs) remains underexplored. This paper presents a pioneering empirical study to investigate the capabilities of LLMs, including GPT-4, GPT-3, Gemma 2, LLaMA 3.1, and Code Llama, in understanding IRs. We analyze their performance across four tasks: Control Flow Graph (CFG) reconstruction, decompilation, code summarization, and execution reasoning. Our results indicate that while LLMs demonstrate competence in parsing IR syntax and recognizing high-level structures, they struggle with control flow reasoning, execution semantics, and loop handling. Specifically, they often misinterpret branching instructions, omit critical IR operations, and rely on heuristic-based reasoning, leading to errors in CFG reconstruction, IR decompilation, and execution reasoning. The study underscores the necessity for IR-specific enhancements in LLMs, recommending fine-tuning on structured IR datasets and integration of explicit control flow models to augment their comprehension and handling of IR-related tasks.

Jiang, Hailong↗
DOE OSTI2023

Impact of Flow Configurations on Response Time and Data Quality in Real-Time, In-Line Fourier Transform Infrared (FTIR) Monitoring of Viscous Flows

The real-time, in-line monitoring of continuous flow concentrations is widely conducted via infrared (IR) spectrometry by using a flow cell connected to a reactive flow stream. For protective purposes, the IR sensor tip is typically offset from the flow. This offset can cause the formation of a stagnant boundary layer above the sensor, especially when dealing with high-viscosity fluids. As a result, the IR signal response time is often controlled by the slow diffusional exchange of fluid in the boundary layer, as confirmed via 2D computational fluid dynamics (CFD) simulations. We evaluated several flow configuration modifications in a typical IR flow cell in order to identify the changes to the flow dynamics that enable improved response times with minimal changes to the cell configuration: the use of (i) vertical flow, where the standard horizontal flow over the sensor is redirected to contact vertically with the sensor, (ii) a static mixer to create radial flow momentum above the IR sensor, and (iii) horizontal or vertical nozzles to direct the flow toward the IR sensor. The vertical flow configuration did not show any significant improvement over the standard horizontal flow configuration. However, the static mixer, horizontal nozzle, and vertical nozzle configurations all resulted in markedly improved response times and signal quality, albeit at the expense of a higher pressure drop across the flow cell. These results point toward straightforward, user-accessible modifications of in-line IR flow cells that result in significant improvements in signal stability and acquisition times.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on Al9Ir2 by Materials Project

Al9Ir2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ir is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Ir–Al bond distances ranging from 2.47–2.61 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a linear geometry to two equivalent Ir atoms. In the second Al site, Al is bonded in a 2-coordinate geometry to two equivalent Ir atoms. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Ir atoms. In the fourth Al site, Al is bonded in a distorted bent 120 degrees geometry to two equivalent Ir atoms. In the fifth Al site, Al is bonded in a distorted bent 150 degrees geometry to two equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba3NaIr2O9 by Materials Project

Ba3NaIr2O9 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na is bonded to six O atoms to form NaO6 octahedra that share corners with six equivalent IrO6 octahedra and faces with six equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 9–13°. There are two shorter (2.25 Å) and four longer (2.28 Å) Na–O bond lengths. There are two inequivalent Ba sites. In the first Ba site, Ba is bonded to twelve O atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent BaO12 cuboctahedra, corners with three equivalent IrO6 octahedra, faces with four equivalent BaO12 cuboctahedra, faces with three equivalent NaO6 octahedra, and faces with four equivalent IrO6 octahedra. The corner-sharing octahedra tilt angles range from 4–16°. There are a spread of Ba–O bond distances ranging from 2.82–3.31 Å. In the second Ba site, Ba is bonded in a 12-coordinate geometry to twelve O atoms. There are a spread of Ba–O bond distances ranging from 2.80–3.33 Å. Ir is bonded to six O atoms to form IrO6 octahedra that share corners with three equivalent BaO12 cuboctahedra, corners with three equivalent NaO6 octahedra, faces with four equivalent BaO12 cuboctahedra, and a faceface with one IrO6 octahedra. The corner-sharing octahedra tilt angles range from 9–13°. There are a spread of Ir–O bond distances ranging from 1.91–2.07 Å. There are five inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to one Na, four Ba, and one Ir atom. In the second O site, O is bonded in a 2-coordinate geometry to four Ba and two equivalent Ir atoms. In the third O site, O is bonded to four Ba and two equivalent Ir atoms to form distorted corner-sharing OBa4Ir2 octahedra. The corner-sharing octahedral tilt angles are 8°. In the fourth O site, O is bonded in a 2-coordinate geometry to one Na, four Ba, and one Ir atom. In the fifth O site, O is bonded in a 2-coordinate geometry to one Na, four Ba, and one Ir atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaIn4Ir by Materials Project

CaIrIn4 crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. Ca is bonded in a 1-coordinate geometry to one Ir and twelve In atoms. The Ca–Ir bond length is 3.06 Å. There are a spread of Ca–In bond distances ranging from 3.33–3.76 Å. Ir is bonded in a 9-coordinate geometry to one Ca and eight In atoms. There are a spread of Ir–In bond distances ranging from 2.65–2.93 Å. There are three inequivalent In sites. In the first In site, In is bonded in a linear geometry to two equivalent Ca and two equivalent Ir atoms. In the second In site, In is bonded in a 2-coordinate geometry to four equivalent Ca and two equivalent Ir atoms. In the third In site, In is bonded in a distorted square co-planar geometry to two equivalent Ca and two equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrIn4Ir by Materials Project

SrIrIn4 crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. Sr is bonded in a 1-coordinate geometry to one Ir and twelve In atoms. The Sr–Ir bond length is 3.23 Å. There are a spread of Sr–In bond distances ranging from 3.43–3.77 Å. Ir is bonded in a 9-coordinate geometry to one Sr and eight In atoms. There are a spread of Ir–In bond distances ranging from 2.63–2.92 Å. There are three inequivalent In sites. In the first In site, In is bonded in a 2-coordinate geometry to four equivalent Sr, two equivalent Ir, and six In atoms. There are a spread of In–In bond distances ranging from 3.20–3.40 Å. In the second In site, In is bonded in a distorted rectangular see-saw-like geometry to two equivalent Sr, two equivalent Ir, and four equivalent In atoms. In the third In site, In is bonded in a linear geometry to two equivalent Sr, two equivalent Ir, and four equivalent In atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y3IrI3 by Materials Project

Y3IrI3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three inequivalent Y sites. In the first Y site, Y is bonded to three equivalent Ir and three I atoms to form distorted edge-sharing YIr3I3 octahedra. There are two shorter (2.79 Å) and one longer (2.92 Å) Y–Ir bond lengths. There are one shorter (3.26 Å) and two longer (3.33 Å) Y–I bond lengths. In the second Y site, Y is bonded in a 6-coordinate geometry to one Ir and five I atoms. The Y–Ir bond length is 2.76 Å. There are a spread of Y–I bond distances ranging from 3.13–3.58 Å. In the third Y site, Y is bonded in a 6-coordinate geometry to two equivalent Ir and four I atoms. Both Y–Ir bond lengths are 2.79 Å. There are a spread of Y–I bond distances ranging from 3.30–3.59 Å. Ir is bonded in a 6-coordinate geometry to six Y atoms. There are three inequivalent I sites. In the first I site, I is bonded in a 5-coordinate geometry to five Y atoms. In the second I site, I is bonded in a distorted T-shaped geometry to three Y atoms. In the third I site, I is bonded in a 4-coordinate geometry to four Y atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y6IrI10 by Materials Project

Y6IrI10 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Y sites. In the first Y site, Y is bonded to one Ir and five I atoms to form a mixture of corner and edge-sharing YIrI5 octahedra. The corner-sharing octahedra tilt angles range from 0–10°. The Y–Ir bond length is 2.75 Å. There are a spread of Y–I bond distances ranging from 3.12–3.33 Å. In the second Y site, Y is bonded to one Ir and five I atoms to form a mixture of distorted corner and edge-sharing YIrI5 octahedra. The corner-sharing octahedra tilt angles range from 0–10°. The Y–Ir bond length is 2.67 Å. There are a spread of Y–I bond distances ranging from 3.06–3.38 Å. In the third Y site, Y is bonded to one Ir and five I atoms to form a mixture of corner and edge-sharing YIrI5 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. The Y–Ir bond length is 2.77 Å. There are a spread of Y–I bond distances ranging from 3.02–3.31 Å. Ir is bonded in an octahedral geometry to six Y atoms. There are five inequivalent I sites. In the first I site, I is bonded in a distorted L-shaped geometry to two Y atoms. In the second I site, I is bonded in a distorted T-shaped geometry to three Y atoms. In the third I site, I is bonded in a distorted T-shaped geometry to three Y atoms. In the fourth I site, I is bonded in a distorted see-saw-like geometry to four Y atoms. In the fifth I site, I is bonded in a 3-coordinate geometry to three Y atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sn5(BIr3)2 by Materials Project

Sn5(Ir3B)2 crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Ir is bonded in a 7-coordinate geometry to two B and five Sn atoms. There are one shorter (2.19 Å) and one longer (2.22 Å) Ir–B bond lengths. There are a spread of Ir–Sn bond distances ranging from 2.72–2.91 Å. There are two inequivalent B sites. In the first B site, B is bonded in a distorted pentagonal pyramidal geometry to six equivalent Ir atoms. In the second B site, B is bonded in a 6-coordinate geometry to six equivalent Ir and three equivalent Sn atoms. All B–Sn bond lengths are 2.71 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to six equivalent Ir atoms. In the second Sn site, Sn is bonded in a 7-coordinate geometry to six equivalent Ir and one B atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiIr3 by Materials Project

LiIr3 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. Li is bonded in a 12-coordinate geometry to ten Ir atoms. There are a spread of Li–Ir bond distances ranging from 2.61–2.78 Å. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 12-coordinate geometry to three equivalent Li atoms. In the second Ir site, Ir is bonded in a 12-coordinate geometry to four equivalent Li atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr3Ir by Materials Project

Zr3Ir crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. there are three inequivalent Zr sites. In the first Zr site, Zr is bonded in a water-like geometry to two equivalent Ir atoms. Both Zr–Ir bond lengths are 2.80 Å. In the second Zr site, Zr is bonded in a distorted water-like geometry to two equivalent Ir atoms. Both Zr–Ir bond lengths are 2.80 Å. In the third Zr site, Zr is bonded in a 4-coordinate geometry to four equivalent Ir atoms. There are two shorter (2.75 Å) and two longer (2.94 Å) Zr–Ir bond lengths. Ir is bonded in a 8-coordinate geometry to eight Zr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2GaIr by Materials Project

Li2IrGa crystallizes in the cubic F-43m space group. The structure is three-dimensional. there are two inequivalent Li sites. In the first Li site, Li is bonded to six equivalent Ir and four equivalent Ga atoms to form distorted LiGa4Ir6 tetrahedra that share corners with eighteen LiIr4 tetrahedra and faces with sixteen LiGa4Ir6 tetrahedra. All Li–Ir bond lengths are 3.00 Å. All Li–Ga bond lengths are 2.60 Å. In the second Li site, Li is bonded to four equivalent Ir atoms to form distorted LiIr4 tetrahedra that share corners with twenty-four LiIr4 tetrahedra and faces with four equivalent LiGa4Ir6 tetrahedra. All Li–Ir bond lengths are 2.60 Å. Ir is bonded in a distorted body-centered cubic geometry to ten Li and four equivalent Ga atoms. All Ir–Ga bond lengths are 2.60 Å. Ga is bonded in a distorted body-centered cubic geometry to four equivalent Li and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗