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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Electronic and magnetic properties of the RuX3 (X = Cl, Br, I) family: two siblings—and a cousin?

Abstract Motivated by reports of metallic behavior in the recently synthesized RuI 3 , in contrast to the Mott-insulating nature of the actively discussed α -RuCl 3 , as well as RuBr 3 , we present a detailed comparative analysis of the electronic and magnetic properties of this family of trihalides. Using a combination of first-principles calculations and effective-model considerations, we conclude that RuI 3 , similarly to the other two members, is most probably on the verge of a Mott insulator, but with much smaller magnetic moments and strong magnetic frustration. We predict the ideal pristine crystal of RuI 3 to have a nearly vanishing conventional nearest-neighbor Heisenberg interaction and to be a quantum spin liquid candidate of a possibly different kind than the Kitaev spin liquid. In order to understand the apparent contradiction to the reported resistivity ρ , we analyze the experimental evidence for all three compounds and propose a scenario for the observed metallicity in existing samples of RuI 3 . Furthermore, for the Mott insulator RuBr 3, we obtain a magnetic Hamiltonian of a similar form to that in the much-discussed α -RuCl 3 and show that this Hamiltonian is in agreement with experimental evidence in RuBr 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Light induced electron spin resonance properties of van der Waals CrX 3 (X = Cl, I) crystals

The research on layered van der Waals (vdW) magnets is rapidly progressing owing to exciting fundamental science and potential applications. In bulk crystal form, CrCl 3 is a vdW antiferromagnet with in-plane ferromagnetic ordering below 17 K, and CrI 3 is a vdW ferromagnet below 61 K. In this paper, we report on the electron spin resonance (ESR) properties of CrCl 3 and CrI 3 single crystals upon photo-excitation in the visible range. We noticed remarkable changes in the ESR spectra upon illumination. In the case of CrCl 3 , at 10 K, the ESR signal is shifted from g = 1.492 (dark) to 1.661 (light), the linewidth increased from 376 to 506 Oe, and the signal intensity is reduced by 1.5 times. Most interestingly, the observed change in the signal intensity is reversible when the light is cycled on/off. We observed almost no change in the ESR spectral parameters in the paramagnetic phase (>20 K) upon illumination. Upon photo-excitation of CrI 3 , the ESR signal intensity is reduced by 1.9 times; the g-value increased from 1.956 to 1.990; the linewidth increased from 1170 to 1260 Oe at 60 K. These findings are discussed by taking into account the skin depth, the slow relaxation mechanism, and the appearance of low-symmetry fields at the photo-generated Cr 2+ Jahn–Teller centers. Such an increase in the g-value as a result of photo-generated Cr 2+ ions is further supported by our many-body wavefunction calculations. This work has the potential to extend to monolayer vdWs magnets by combining ESR spectroscopy with optical excitation and detection.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Performance of alloy 600 in flowing commercial Cl salt at 600°-750°C

For the next generation of concentrating solar power (CSP) plants, K-Mg-Na chloride salts are being explored as a potential higher temperature thermal storage medium. However, there are concerns about compatibility of structural alloys with the salt. To move beyond simple static pot compatibility experiments while a pumped salt loop is being constructed, thermal convection loops were constructed from ~16wt.%Cr Ni-based alloy 600 and operated for 100-1000 h with peak temperatures of 700° and 750°C. These experiments indicated that alloy 600 was compatible up to 700°C with purified (i.e. low O2-) or dried (low H2O) industrial-sourced Mg-K-Na chloride salt with <10 µm/yr loss. Mass transfer was observed from the hot leg to the cold leg in each experiment and more surface deposits were observed with the dried salt. Post-exposure room temperature tensile tests showed minimal degradation of alloy 600 under these conditions.

Pint, Bruce↗
DOE OSTI2020

Association of Cl with C 2 H 2 by unified variable-reaction-coordinate and reaction-path variational transition-state theory

Significance A key issue in chemical kinetics is advancing the theoretical framework to handle reactions beyond the domain of textbook transition-state theory by including––for example––anharmonicity, barrierless transition states, transition states in series, and the effect of conformational flexibility on equilibrium constants. Other key issues are validating affordable electronic structure methods for direct dynamics and the direct calculation of high-pressure limiting rate constants, which are often obtainable experimentally only by extrapolation. The present article addresses all these issues for a prototype radical–molecule association reaction and thereby demonstrates how to combine improved theoretical methods to provide rate constants in cases where experimental data are uncertain or missing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Fabrication of Low-Cost Large-Volume Ceramic A 2 HfX 6 (A= Cs or Tl, X = Cl, Br, or I) Scintillators for Gamma Ray Detection (SBIR Phase I Final Technical Report)

Scintillator crystals play an important role in the radiation detection field. Widespread use of scintillators as gamma-ray detectors is largely generated by their extensive availability and tunable properties, such high light output, high stopping power (Z eff ), fast decay time, and good proportionality. Additionally, the cost for manufacturing a scintillation detector like NaI:Tl is usually considerably lower than the cost for manufacturing a semiconductor detector like CdZnTe. Because there is no such thing as an ideal scintillation material, an application requiring certain detection characteristics may incorporate a scintillator tailored to its specific properties. The vast variety of applications and requirements necessitates more research into new scintillation materials and/or better methods of producing existing materials.The goal of this project was to grow low cost and environmentally stable inorganic transparent ceramic scintillators with excellent gamma ray resolution, excellent energy proportionality, excellent detection efficiency due to high density (>5 g/cm 3 ) and very high Z eff (55-80), and good light yields (>40,000 ph/MeV). In Phase I Xtallized Intelligence, Inc. (XI, Inc) developed a novel ceramic fabrication technique to produce low cost and environmentally stable highly efficient inorganic transparent ceramic scintillators of various dimensions. XI, Inc., collaborating with Fisk University (Fisk), investigated the scintillation properties of these new ceramic scintillators and compared them to in their single crystal counterparts. The results of this Phase I project show that successful production of high-quality inorganic halide ceramic scintillators Cs 2 HfCl 6 (CHC) and Tl 2 HfCl 6 (THC). Both ceramic CHC and THC scintillators have achieved good performance close to the performance of their single crystal counterparts. Fabricating these inorganic ceramic scintillators mitigate many issues encountered during conventional bulk crystal growth by melt methods. Additional benefits of the ceramic fabrication technique include high production yield, low production cost, fast production time, and no material waste Inorganic transparent ceramic scintillators produced in this project will enhance cost effectiveness at the instrument level based on low projected cost of the proposed compounds, as much smaller crystal sizes would be required to achieve similar efficiency as current radioisotope identification devices (RIID’s) used in homeland security applications as well as spectrometers in high energy physics applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Longitudinal Solid P Longitudinal Solid Polarized Target for CL get for CLAS12 and Study of Spin AS12 and Study of Spin Structure of Nucleons

A suite of experiments measuring target-spin observables in electron-nucleon scattering (dubbed Run Group C) was conducted at Jefferson Lab's Hall B in Newport News, VA with a new polarized nuclear target known as 'APOLLO' (Ammonia POLarized LOngitudinally). This innovative target is engineered to seamlessly integrate with the advanced 12GeV CEBAF (Continuous Electron Beam Accelerator Facility) accelerator and the Hall B CLAS12 (12 GeV CEBAF Large Acceptance Spectrometer) detector array. The 'APOLLO' target harnesses the power of Dynamic Nuclear Polarization (DNP) to achieve longitudinal polarization of solid ammonia, thereby creating a net polarization in both protons (NH3) and deuterons (ND3). These samples are subjected to a 5 Tesla magnetic field produced by the CLAS12 spectrometer central solenoid, cooled to 1 K using helium evaporation, and subsequently exposed to microwave radiation at a frequency of 140 GHz. This project was made possible through a collaborative partnership between the Jefferson Lab Target Group, Old Dominion University, University of Virginia, Christopher Newport University, and the CLAS Collaboration. Integrating the APOLLO target into CLAS12 presented unique challenges because of its specific spatial and dimensional constraints. This dissertation will highlight the innovative solutions developed to address these challenges, including the creation of a new target material transport system, the incorporation of superconducting magnetic correction coils, and the development of a customized Nuclear Magnetic Resonance (NMR) system. In addition to a detailed description of the development and operation of APOLLO, and an overview of RGC, this document also describes the global data fitting of proton asymmetries in the Deep Inelastic scattering (DIS) and the Resonance regions, and it offers insights into the comprehensive analysis of target polarization data.

Pandey, Pushpa↗
DOE OSTI2021

Observation of a New Polyhalide Phase in Ag-Cl 2 System at High Pressure

In this short contribution, we examine Raman spectroscopic data from high-pressure and high-temperature experiments with an Ag-Cl2 system, and find that they are in good agreement with previously observed and calculated spectra of polychloride species. Our results imply the formation of a hitherto unknown AgClx compound, which warrants further study.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaP5Cl18O17 by Materials Project

LaP5O17Cl18 crystallizes in the monoclinic P2_1 space group. The structure is zero-dimensional and consists of two LaP5O17Cl18 clusters. La is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of La–O bond distances ranging from 2.51–2.71 Å. There are five inequivalent P sites. In the first P site, P is bonded in a tetrahedral geometry to one O and three Cl atoms. The P–O bond length is 1.48 Å. All P–Cl bond lengths are 1.99 Å. In the second P site, P is bonded in a tetrahedral geometry to one O and three Cl atoms. The P–O bond length is 1.48 Å. All P–Cl bond lengths are 1.99 Å. In the third P site, P is bonded in a tetrahedral geometry to one O and three Cl atoms. The P–O bond length is 1.48 Å. There is two shorter (1.99 Å) and one longer (2.00 Å) P–Cl bond length. In the fourth P site, P is bonded in a tetrahedral geometry to one O and three Cl atoms. The P–O bond length is 1.48 Å. There is two shorter (1.99 Å) and one longer (2.00 Å) P–Cl bond length. In the fifth P site, P is bonded in a tetrahedral geometry to one O and three Cl atoms. The P–O bond length is 1.48 Å. There is two shorter (1.99 Å) and one longer (2.00 Å) P–Cl bond length. There are seventeen inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one La and one P atom. In the second O site, O is bonded in a distorted linear geometry to one La and one P atom. In the third O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.44 Å. In the fourth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.45 Å. In the fifth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.45 Å. In the sixth O site, O is bonded in a distorted single-bond geometry to one La and one P atom. In the seventh O site, O is bonded in a bent 120 degrees geometry to one La and one Cl atom. The O–Cl bond length is 1.51 Å. In the eighth O site, O is bonded in a water-like geometry to one La and one Cl atom. The O–Cl bond length is 1.50 Å. In the ninth O site, O is bonded in a distorted linear geometry to one La and one P atom. In the tenth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.44 Å. In the eleventh O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.45 Å. In the twelfth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.45 Å. In the thirteenth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.46 Å. In the fourteenth O site, O is bonded in a distorted water-like geometry to one La and one Cl atom. The O–Cl bond length is 1.49 Å. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to one La and one Cl atom. The O–Cl bond length is 1.49 Å. In the sixteenth O site, O is bonded in a distorted single-bond geometry to one La and one P atom. In the seventeenth O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.45 Å. There are eighteen inequivalent Cl sites. In the first Cl site, Cl is bonded in a single-bond geometry to one P atom. In the second Cl site, Cl is bonded in a single-bond geometry to one P atom. In the third Cl site, Cl is bonded in a single-bond geometry to one P atom. In the fourth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the fifth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the sixth Cl site, Cl is bonded in a tetrahedral geometry to four O atoms. In the seventh Cl site, Cl is bonded in a single-bond geometry to one P atom. In the eighth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the ninth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the tenth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the eleventh Cl site, Cl is bonded in a single-bond geometry to one P atom. In the twelfth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the thirteenth Cl site, Cl is bonded in a tetrahedral geometry to four O atoms. In the fourteenth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the fifteenth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the sixteenth Cl site, Cl is bonded in a single-bond geometry to one P atom. In the seventeenth Cl site, Cl is bonded in a tetrahedral geometry to four O atoms. In the eighteenth Cl site, Cl is bonded in a single-bond geometry to one P atom.

36 MATERIALS SCIENCE↗