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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Device Performance of Emerging Photovoltaic Materials (Version 3)

Abstract Following the 2nd release of the “Emerging PV reports,” the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer‐reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open‐circuit voltage, short‐circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the “Emerging PV reports” extends the scope toward triple junction solar cells.

14 SOLAR ENERGY↗
DOE OSTI2023

Spin-orbital order and excitons in magnetoresistive HoBi

The magnetism of the rocksalt fcc rare-earth monopnictide HoBi, a candidate topological material with extreme magnetoresistance, is investigated. From the Ho 3+ non-Kramers J=8 spin-orbital multiplet, the cubic crystal electric field yields six nearly degenerate low-energy levels. These constitute an anisotropic magnetic moment with a Jahn-Teller-like coupling to the lattice. In the cubic phase for T>T N =5.72(1)K, the paramagnetic neutron scattering is centered at k=($\frac{1}{2}$$\frac{1}{2}$$\frac{1}{2}$) and was fit to dominant antiferromagnetic interactions between Ho spins separated by {100} and ferromagnetic interactions between spins displaced by {$\frac{1}{2}$ $\frac{1}{2}$ 0}. For T < T N , a type-II AFM long-range order with k=($\frac{1}{2}$$\frac{1}{2}$$\frac{1}{2}$) develops along with a tetragonal lattice distortion. While neutron diffraction from a multidomain sample cannot unambiguously determine the spin orientation within a domain, the bulk magnetization, structural distortion, and our measurements of the magnetic excitations all show the easy axis coincides with the tetragonal axis. Finally, the weakly dispersive excitons for T < T N can be accounted for by a spin Hamiltonian that includes the crystal electric field and exchange interactions within the random phase approximation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

BCG alignment with the locations of cluster members and the large-scale structure out to 10 R 200

Using a sample of >200 clusters, each with typically 100–200 spectroscopically confirmed cluster members, we search for a signal of alignment between the position angle (PA) of the Brightest Cluster Galaxy (BCG) and the distribution of cluster members on the sky about the cluster centre out to projected distances of 3 R 200 . The deep spectroscopy, combined with corrections for spectroscopic incompleteness, makes our sample ideal to determine alignment signal strengths. We also use an SDSS based skeleton of the filamentary large-scale structure (LSS), and measure BCG alignment with the location of the LSS skeleton segments on the sky out to projected distances of 10 R 200 . The alignment signal is measured using three separate statistical measures; Rao’s spacing test (U), Kuiper’s V parameter (V), and the Binomial probability test (P). The significance of the BCG alignment signal with both cluster members and LSS segments is extremely high (1 in a million chance or less to be drawn randomly from a uniform distribution). We investigate a wide set of parameters that may influence the strength of the alignment signal. Clusters with more elliptical-shaped BCGs show stronger alignment with both their cluster members and LSS segments. Also, selecting clusters with closely connected filaments, or using a luminosity-weighted LSS skeleton, increases the alignment signal significantly. Alignment strength decreases with increasing projected distance. Combined, these results provide strong evidence for the growth of clusters and their BCGs by preferential feeding along the direction of the filaments in which they are embedded.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Comprehensive Synthesis and Structural Trends in Tetramethyl Diglycolamide (TMDGA) Nitrate Complexes with Lanthanides and Americium

Complexes of N,N,N',N'-tetramethyl diglycolamide (TMDGA), a hydrophilic diglycolamide (DGA) proposed as an aqueous phase holdback reagent, have been crystallized for the majority of the lanthanide series (excluding promethium), yttrium, and americium to deepen our structural understanding of trivalent metal ion (M 3+ ) DGA coordination compounds in the presence of nitrate counter-anions. The presented collection of 16 complexes with accompanying single-crystal structures, taking formulas [M(TMDGA) 3 ][M(NO 3 ) 6 ] (M = La, Ce, Pr, Nd, Sm, Am), [M(TMDGA) 3 ][M(NO 3 ) 5 (H 2 O)] 1–x [M(NO 3 ) 4 (H 2 O) 2 ] x (NO 3 ) 1+x (M = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), [M(TMDGA) 3 ] 2 [M(NO 3 ) 4 (H 2 O) 2 ] 0.75 [M(NO 3 ) 5 (H 2 O)] 1.25 (NO 3 ) 2.75 ·H 2 O (M = Lu), and [M(TMDGA) 3 ][M(NO 3 ) 5 (H 2 O)](NO 3 )·CH 3 OH (M = Y) were all synthesized via solvent diffusion of reaction mixtures containing the metal nitrate M(NO 3 ) 3 ·nH 2 O and TMDGA. Single-crystal X-ray diffraction analyses of these new structures show that each TMDGA complex comprises of three TMDGA ligands coordinating the metal ion via carbonyl and etheric oxygen atoms forming [M(TMDGA) 3 ] 3+ cations. Spectroscopy measurements under high pressure displayed notable differences in the f → f transition shifting between that of Nd(III) and Am(III). Shifting of transitions by 2.0 nm were observed in Nd up to 8.50 ± 0.09 GPa, while Am saw shifting between 11.0 to 13.5 nm at pressures up to 20.06 ± 1.90 GPa. The local geometry in these complexes is a distorted spherical capped square antiprism (CSAPR-9) except for of the yttrium complex, which exhibits a distorted spherical tricapped trigonal prismatic (TCTPR-9) geometry. Further, the anions that form concomitantly with the TMDGA complexes are composed of hexanitrato species for the early lanthanide ions (lanthanum to samarium); whereas the remaining smaller lanthanides did not possess sufficiently large ionic radii to coordinate six bidentate nitrate anions, instead, one or two nitrate anions are situated in the outer sphere. The systematic progression of changes in the anionic environments of these complexes outlines the changing coordination habits afforded by the lanthanide contraction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ho4Zr3O12 by Materials Project

Ho4Zr3O12 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.20–2.69 Å. In the second Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.24–2.61 Å. In the third Ho3+ site, Ho3+ is bonded to seven O2- atoms to form distorted HoO7 pentagonal bipyramids that share a cornercorner with one ZrO6 octahedra and an edgeedge with one ZrO6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of Ho–O bond distances ranging from 2.19–2.51 Å. In the fourth Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.22–2.62 Å. There are three inequivalent Zr4+ sites. In the first Zr4+ site, Zr4+ is bonded to six O2- atoms to form ZrO6 octahedra that share a cornercorner with one HoO7 pentagonal bipyramid and an edgeedge with one HoO7 pentagonal bipyramid. There are a spread of Zr–O bond distances ranging from 2.10–2.17 Å. In the second Zr4+ site, Zr4+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Zr–O bond distances ranging from 2.10–2.62 Å. In the third Zr4+ site, Zr4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Zr–O bond distances ranging from 2.08–2.23 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Ho3+ and two Zr4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ho3+ and two Zr4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two Ho3+ and two Zr4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Zr4+ atoms. In the fifth O2- site, O2- is bonded to three Ho3+ and one Zr4+ atom to form distorted OHo3Zr tetrahedra that share corners with six OHo2Zr2 tetrahedra and edges with three OHo3Zr tetrahedra. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Ho3+ and two Zr4+ atoms. In the seventh O2- site, O2- is bonded to two Ho3+ and two equivalent Zr4+ atoms to form a mixture of distorted edge and corner-sharing OHo2Zr2 tetrahedra. In the eighth O2- site, O2- is bonded to two Ho3+ and two equivalent Zr4+ atoms to form distorted OHo2Zr2 tetrahedra that share corners with six OHo3Zr tetrahedra and edges with three OHo2Zr2 tetrahedra. In the ninth O2- site, O2- is bonded to three Ho3+ and one Zr4+ atom to form a mixture of edge and corner-sharing OHo3Zr tetrahedra. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to three Ho3+ and one Zr4+ atom. In the eleventh O2- site, O2- is bonded to three Ho3+ and one Zr4+ atom to form a mixture of edge and corner-sharing OHo3Zr tetrahedra. In the twelfth O2- site, O2- is bonded to three Ho3+ and one Zr4+ atom to form distorted OHo3Zr tetrahedra that share corners with six OHo3Zr tetrahedra and edges with three OHo2Zr2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Controlling quantum many-body dynamics in driven Rydberg atom arrays

Dynamic stabilization of an array Large-scale systems comprising one-dimensional chains and two-dimensional arrays of excited atoms held in a programmable optical lattice are a powerful platform with which to simulate emergent phenomena. Bluvstein et al. built an array of up to 200 Rydberg atoms and subjected the system to periodic excitation. Under such driven excitation, they found that the array of atoms stabilized, freezing periodically into what looked like time crystals. Understanding and controlling the dynamic interactions in quantum many-body systems lies at the heart of contemporary condensed matter physics and the exotic phenomena that can occur. Science , this issue p. 1355

Science & Technology - Other Topics↗
DOE OSTI2024

Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of the 6⁢ H perovskite Ba 3 ⁢Ho⁢Ru 2⁢ O 9

The compound Ba 3 HoRu 2 O 9 magnetically orders at 50 K (T N1 ), followed by another complex magnetic ordering at 10.2 K (T N2 ). The second magnetic phase transition was characterized by the coexistence of two competing magnetic ground states associated with two different magnetic wave vectors (K 1 = 0.5 0 0 and K 2 = 0.25 0.25 0). The multiferroicity and magnetoelectric coupling were predicted below T N2 in these 4d-based materials. Here, in this work, we have discussed the origin of spin-driven ferroelectricity, which is not known yet, and the nature of magnetoelectric domains. We have investigated the compound through time-of-flight neutron diffraction, synchrotron x-ray diffraction (XRD), ac susceptibility, frequency-dependent complex dielectric spectroscopy, and dc magnetization under external pressure. We have demonstrated that the noncollinear structure involving two different magnetic ions, Ru (4d) and Ho (4f), breaks the spatial inversion symmetry via inverse Dzyaloshinskii-Moriya (DM) interaction through strong 4d-4f magnetic correlation, which shifts the oxygen atoms and results in nonzero polarization. Such an observation of inverse DM interaction from two different magnetic ions which cause ferroelectricity is rarely observed. The stronger spin-orbit coupling of 4d orbital might play a major role in creating DM interaction of noncollinear spins. We have systematically studied the spin and dipolar dynamics, which exhibit intriguing behavior with shorter coherence lengths of second magnetic phase associated with the k 2 wave vector. The results manifest the development of finite-size magnetoelectric domains instead of true long-range ordering, which justifies the experimentally obtained low value of ferroelectric polarization. The lattice parameters and volume show a sharp anomaly at T N2 obtained by analyzing the temperature-dependence XRD, which is consistent with the ferroelectric transition, predicting a noncentrosymmetric space group, $P\bar{6}2c$, for this compound. Furthermore, we have investigated the effect of external pressure on this complex magnetism. The result reveals an enhancement of ordering temperature by the application of external pressure (~1.6 K/GPa). The external pressure might favor stabilizing the magnetic ground state associated with second magnetic phase. Our study shows an unconventional mechanism of spin-driven ferroelectricity involving inverse DM interaction between Ru (4d) and Ho (4f) magnetic ions due to strong 4d-4f cross coupling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1994

OSSE observations of the Crab pulsar

We present results of the Compton Gamma-Ray Observatory (CGRO) Oriented Scintillation Spectrometer Experiment (OSSE) observations of the Crab pulsar, made during MJD 48373-48406 (1991 April 27 - 1991 May 30) and MJD 48798-48804 (1992 June 25 - 1992 July 1). Pulsar light curves and spectra over the approximately 0.05 to 10 MeV range are presented. The arrival time of the gamma-ray peak and the radio peak agree to within 30 microsec which is better than the approximately 300 microsec accuracy of the measurements. The overall pulse phase averaged spectrum in the 0.1 - 10 MeV range is well-fit by a power law of the form 0.05 x (E/0.13 MeV)exp(-(1.99 +/- 0.03)) photons/sq cm/s. The outer-gap model (with gap parameter equal to 0.46) provided to us by Ho agrees with the data to better than 20%. The spectra of the bridge and second peak are slightly harder than the first peak as measured by the hardness ratio (approximately 110 - 220 keV)/(approximately 50 - 105 keV): P1 = 0.54 +/- 0.01, P2 = 0.63 +/- 0.01, bridge = 0.68 +/- 0.03. The phase of the two peaks in the light curve is constant over the 50 - 550 keV range to within the accuracy of the measurements (better than 0.02 in phase). No evidence was found for variability of the light curve on timescales from 2 minutes (less than a factor of 1.8) to 1 year (less than a factor of 1.06), where these are 3 sigma upper limits. However, when we examine the historical database, we find, in agreement with Nolan et al. (1993), that there is evidence for a 13 year variation in the ratio of the intensity of peak 2 to peak 1. We show that if this is interpreted as being due to precession (which changes the relative view of the intrinsic gamma-ray pulse as seen on earth), the variation is consistent with models of neutron star structure. The optical data may be in conflict with the interpretation however. We found no statistically significant lines in the 50 - 550 keV range in the spectrum. The average 3 sigma upper limits in 10(exp -3) photons/sq cm/s for lines at 0.073, 0.078, 0.4, 0.44, 0.511, and 0.545 MeV are 0.3, 0.5, 0.6, 0.5, and 0.1.

Ulmer, M. P.↗
DOE OSTI2021

First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon

Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density n_e of order 10^4-7 cm-3, magnetic field strength B of order 1-30 G, and electron temperature Te of order (1-12) x 10^10 K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3-20) x 10^-4 Msun yr-1.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

CPAP Ventilators Needed for Rapid Response to COVID-19 by Modification of CPAP Equipment

Early on in the COVID-19 pandemic, potential ventilator shortages were a critical issue identified by national health care providers. Capacity modeling at the time suggested patient demand may exceed ventilator supply. Thus, the challenge became finding an urgent interim solution to meet health care needs. Our initial hypothesis was that CPAP technology could be modified to provide similar functionality to a ventilator, relieving demand and allowing physicians to decide which patients need high end machines, ultimately saving lives. In conjunction with medical experts and pulmonologists, we were able to identify three key thrusts associated with this research problem: (1) modification of CPAP technology to allow for 02 input that would be capable of providing ventilation; (2) development of an alarming function that would provide real-time audible alarms to alert medical personnel to critical conditions, which would be used inline with CPAP technology; and (3) a method of sterilizing expiratory air from such a system in order to protect medical personnel from biohazard, since CPAPs vent to the atmosphere. We were unable to realize results for thrust 1 (CPAP modification for 02); we identified potential safety issues associated with utilizing medical grade oxygen with a common CPAP device. In order to characterize and mitigate these issues, we would need to partner closely with a device manufacturer; such a partnership could not be achieved in the timeframe needed for this rapid response work. However, we determined that some medical grade BiPAP devices do not need this modification and that the significant progress on thrusts 2 and 3 would be sufficient to buy down risk of a massive ventilator shortage. Our team built a prototype alarm system that can be utilized with any assistive respiratory device to alert on all key conditions identified by medical personnel (high pressure, low pressure, apnea, loss of power, low battery). Finally, our team made significant progress in the rapid prototyping and demonstration of an inline UV air purifier device. The device is cost efficient and can be manufactured at scale with both commercially available and additively manufactured parts. Initial tests with SARS-CoV-2 analog bacteriophage MS2 show 99% efficacy at reducing bioburden. Following a successful demonstration of the prototype device with medical personnel, we were able to obtain follow-on (non-LDRD) funding to provide additional device characterization, validation, and production in order to respond to an immediate regional need.

42 ENGINEERING↗
DOE OSTI2022

Pressure-induced shift of effective Ce valence, Fermi energy and phase boundaries in CeOs 4 Sb 12

Abstract CeOs 4 Sb 12 , a member of the skutterudite family, has an unusual semimetallic low-temperature L -phase that inhabits a wedge-like area of the field H —temperature T phase diagram. We have conducted measurements of electrical transport and megahertz conductivity on CeOs 4 Sb 12 single crystals under pressures of up to 3 GPa and in high magnetic fields of up to 41 T to investigate the influence of pressure on the different H – T phase boundaries. While the high-temperature valence transition between the metallic H -phase and the L -phase is shifted to higher T by pressures of the order of 1 GPa, we observed only a marginal suppression of the S -phase that is found below 1 K for pressures of up to 1.91 GPa. High-field quantum oscillations have been observed for pressures up to 3.0 GPa and the Fermi surface of the high-field side of the H -phase is found to show a surprising decrease in size with increasing pressure, implying a change in electronic structure rather than a mere contraction of lattice parameters. We evaluate the field-dependence of the effective masses for different pressures and also reflect on the sample dependence of some of the properties of CeOs 4 Sb 12 which appears to be limited to the low-field region.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

The Kinetic Consequences of Water on Catalytic Methane Pyrolysis

Hydrogen production from biomass and natural gas has emerged as a prominent research area in response to the growing demand for energy from alternative sources that minimize CO 2 emissions. In this study, we investigate the impact of water, which is present in and generated from biomass-derived streams, on carbon nanotube (CNT) growth and hydrogen production during methane decomposition using Ni–Mo/MgO as a catalyst. We reveal here that the role of water on CNT growth is highly complex; its effect depends on the stage of growth at which the water is incorporated. When water is introduced at the beginning of methane decomposition ( t = 0 h), methane conversion rates are negatively impacted. We hypothesize that water inhibits the significant phase changes the Ni–Mo/MgO catalyst undergoes during catalyst carburization. In contrast, the incorporation of a small percentage of water after a stabilization period ( t = 3 h) results in methane conversion rate enhancements that scale with the introduced water partial pressure as water selectively reacts with amorphous carbon deposits that lead to catalyst deactivation, thus prolonging the lifetime of some of the most active sites. Moreover, water incorporation after stabilization significantly reduces the apparent activation energy. Density Functional Theory (DFT) calculations reveal that water preferentially interacts with carbon fragments on the catalyst surface to remove carbon deposits with a barrier lower than that required for methane activation, further supporting its role in cleaning active sites on the catalyst surface. Characterization of the resulting carbon nanotubes reveals the formation of more graphitic materials produced in the presence of water, highlighting the impact of water on nanotube properties. These results provide clarity toward the many ways in which water, or cofeeding of biomass-derived materials, may impact catalytic methane pyrolysis rates.

carbon nanotubes↗
DOE OSTI2020

Materials Data on HoTe2ClO5 by Materials Project

HoTe2O5Cl crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one HoTe2O5Cl sheet oriented in the (0, 0, 1) direction. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 6-coordinate geometry to six O2- and one Cl1- atom. There are a spread of Ho–O bond distances ranging from 2.28–2.36 Å. The Ho–Cl bond length is 2.88 Å. In the second Ho3+ site, Ho3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.30–2.56 Å. There are four inequivalent Te4+ sites. In the first Te4+ site, Te4+ is bonded in a 4-coordinate geometry to four O2- and one Cl1- atom. There are a spread of Te–O bond distances ranging from 1.89–2.55 Å. The Te–Cl bond length is 3.20 Å. In the second Te4+ site, Te4+ is bonded in a 4-coordinate geometry to four O2- and one Cl1- atom. There are a spread of Te–O bond distances ranging from 1.89–2.59 Å. The Te–Cl bond length is 3.14 Å. In the third Te4+ site, Te4+ is bonded in a 4-coordinate geometry to four O2- and one Cl1- atom. There are a spread of Te–O bond distances ranging from 1.92–2.35 Å. The Te–Cl bond length is 3.01 Å. In the fourth Te4+ site, Te4+ is bonded in a 4-coordinate geometry to four O2- and one Cl1- atom. There are a spread of Te–O bond distances ranging from 1.91–2.36 Å. The Te–Cl bond length is 3.09 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two Te4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Te4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ho3+ and one Te4+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Te4+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+ and two Te4+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Te4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+ and two Te4+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ho3+ and one Te4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Te4+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Te4+ atoms. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Ho3+ atom. In the second Cl1- site, Cl1- is bonded in a 4-coordinate geometry to four Te4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Crystal Structures, Optical Behavior, and Magnetic Properties in Hydrated Lanthanide Iron Sulfates

Single crystals of LnFe(SO 4 ) 3 (H 2 O) 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm; compounds 1–11) and LnFe(SO 4 ) 3 (H 2 O) (Ln = Tm, Yb, Lu; compounds 12–14) were synthesized under hydrothermal conditions. Single-crystal X-ray diffraction (SCXRD) analysis revealed that the dihydrated compounds (1–11) crystallize in centrosymmetric (CS) structures, with the lanthanide ions adopting eight-coordinate geometries. In contrast, the monohydrated compounds (12–14) exhibit noncentrosymmetric (NCS) structures, where the lanthanide ions are seven-coordinated. Vibrating sample magnetometry (VSM) confirmed that compounds 2, 4, and 7–11 are paramagnetic below 400 K, with compound 8 displaying the highest magnetic susceptibility. Compounds 1, 5, 6, 13, and 14 show a sharp increase in magnetic susceptibility at Néel temperatures ( T N ) of approximately 72, 76, 70, 58, and 56 K, respectively, indicating antiferromagnetic ordering. High-temperature magnetic susceptibility measurements further support the presence of antiferromagnetic transitions in these compounds. Second harmonic generation (SHG) measurements showed that the noncentrosymmetric Yb (compound 13) and Lu (compound 14) compounds exhibit SHG intensities of 0.3× and 1.6× that of potassium dihydrogen phosphate (KDP), respectively.

anions↗
DOE OSTI2020

Materials Data on Ho7C2I12N by Materials Project

Ho7C2NI12 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are seven inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to one C3- and five I1- atoms to form distorted HoCI5 octahedra that share corners with two HoC2I5 pentagonal bipyramids, an edgeedge with one HoCI5 octahedra, and edges with two HoC2I5 pentagonal bipyramids. The Ho–C bond length is 2.20 Å. There are a spread of Ho–I bond distances ranging from 2.96–3.33 Å. In the second Ho3+ site, Ho3+ is bonded to one C3- and five I1- atoms to form distorted HoCI5 octahedra that share an edgeedge with one HoCI5 octahedra and edges with two HoC2I5 pentagonal bipyramids. The Ho–C bond length is 2.19 Å. There are a spread of Ho–I bond distances ranging from 2.97–3.38 Å. In the third Ho3+ site, Ho3+ is bonded in a distorted single-bond geometry to two C3-, one N3-, and four I1- atoms. There are one shorter (2.59 Å) and one longer (2.62 Å) Ho–C bond lengths. The Ho–N bond length is 2.16 Å. There are a spread of Ho–I bond distances ranging from 3.06–3.24 Å. In the fourth Ho3+ site, Ho3+ is bonded in a distorted L-shaped geometry to two equivalent N3- and four I1- atoms. There are one shorter (2.18 Å) and one longer (2.19 Å) Ho–N bond lengths. There are a spread of Ho–I bond distances ranging from 3.29–3.37 Å. In the fifth Ho3+ site, Ho3+ is bonded to two C3- and five I1- atoms to form distorted HoC2I5 pentagonal bipyramids that share a cornercorner with one HoCI5 octahedra, a cornercorner with one HoC2I5 pentagonal bipyramid, edges with two HoCI5 octahedra, an edgeedge with one HoC2I5 pentagonal bipyramid, and a faceface with one HoC2I5 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 10°. There are one shorter (2.47 Å) and one longer (2.50 Å) Ho–C bond lengths. There are a spread of Ho–I bond distances ranging from 3.00–3.49 Å. In the sixth Ho3+ site, Ho3+ is bonded to two C3- and five I1- atoms to form distorted HoC2I5 pentagonal bipyramids that share a cornercorner with one HoCI5 octahedra, a cornercorner with one HoC2I5 pentagonal bipyramid, edges with two HoCI5 octahedra, an edgeedge with one HoC2I5 pentagonal bipyramid, and a faceface with one HoC2I5 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 3°. There are one shorter (2.50 Å) and one longer (2.51 Å) Ho–C bond lengths. There are a spread of Ho–I bond distances ranging from 3.01–3.41 Å. In the seventh Ho3+ site, Ho3+ is bonded in a distorted single-bond geometry to two C3-, one N3-, and four I1- atoms. There are one shorter (2.61 Å) and one longer (2.62 Å) Ho–C bond lengths. The Ho–N bond length is 2.17 Å. There are a spread of Ho–I bond distances ranging from 3.09–3.25 Å. There are two inequivalent C3- sites. In the first C3- site, C3- is bonded in a 6-coordinate geometry to five Ho3+ and one C3- atom. The C–C bond length is 1.44 Å. In the second C3- site, C3- is bonded in a 6-coordinate geometry to five Ho3+ and one C3- atom. N3- is bonded to four Ho3+ atoms to form NHo4 tetrahedra that share a cornercorner with one IHo4 trigonal pyramid, an edgeedge with one NHo4 tetrahedra, and an edgeedge with one IHo4 trigonal pyramid. There are twelve inequivalent I1- sites. In the first I1- site, I1- is bonded in a 2-coordinate geometry to two Ho3+ atoms. In the second I1- site, I1- is bonded in a distorted bent 120 degrees geometry to two Ho3+ atoms. In the third I1- site, I1- is bonded in a 2-coordinate geometry to two Ho3+ atoms. In the fourth I1- site, I1- is bonded in a distorted T-shaped geometry to three Ho3+ atoms. In the fifth I1- site, I1- is bonded in a 3-coordinate geometry to three Ho3+ atoms. In the sixth I1- site, I1- is bonded in a distorted L-shaped geometry to two Ho3+ atoms. In the seventh I1- site, I1- is bonded in a 3-coordinate geometry to three Ho3+ atoms. In the eighth I1- site, I1- is bonded to four Ho3+ atoms to form distorted IHo4 trigonal pyramids that share a cornercorner with one NHo4 tetrahedra and an edgeedge with one NHo4 tetrahedra. In the ninth I1- site, I1- is bonded in a 3-coordinate geometry to three Ho3+ atoms. In the tenth I1- site, I1- is bonded in a distorted L-shaped geometry to two Ho3+ atoms. In the eleventh I1- site, I1- is bonded in a 3-coordinate geometry to three Ho3+ atoms. In the twelfth I1- site, I1- is bonded in a 3-coordinate geometry to three Ho3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way

We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 ± 2.3 μas (68% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 × 10$^{6}$ M $_{⊙}$, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50°), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 10$^{3}$–10$^{5}$ gravitational radii to event-horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Evolution of the electronic structure in Ta 2 NiSe 5 across the structural transition revealed by resonant inelastic x-ray scattering

We utilized high-energy-resolution resonant inelastic X-ray scattering (RIXS) at both the Ta and Ni L 3 -edges to map out element-specific particle-hole excitations in Ta 2 NiSe 5 across the phase transition. Our results reveal a momentum dependent gap-like feature in the low energy spectrum, which agrees well with the band gap in element-specific joint density of states calculations based on ab initio estimates of the electronic structure in both the low temperature monoclinic and the high temperature orthorhombic structure. Below T c , the RIXS energy-momentum map shows a minimal gap at the Brillouin zone center (~0.16 eV), conforming that Ta 2 NiSe 5 possesses a direct band gap in its low temperature ground state. However, inside the gap, no signature of anticipated collective modes with an energy scale comparable to the gap size can be identified. Upon increasing the temperature to above T c , whereas the gap at the zone center closes, the RIXS map at finite momenta still possesses the gross features of the low temperature map, suggesting a substantial mixing between the Ta and Ni orbits in the conduction and valence bands, which does not change substantially across the phase transition. Our experimental observations and comparison to the theoretical calculations lend further support that the phase transition and the corresponding gap opening in Ta 2 NiSe 5 is largely structural by nature with possible minor contribution from the putative exciton condensate.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Comprehensive Characterization of Water Group Ion Composition and Distributions in Saturn's Magnetosphere With Cassini Plasma Spectrometer Data

Saturn's magnetosphere is continuously supplied with neutrals from the Enceladus plume and the icy rings, which undergo ionization and charge-exchange to form a complex water-group plasma environment. While the Cassini Plasma Spectrometer (CAPS) instrument has provided extensive compositional information, detailed separation of individual water-group ion species in time-of-flight (TOF) data has not previously been achieved. In this study, we perform forward modeling of CAPS-IMS energy-per-charge (E/Q) and TOF spectra obtained between 2004 and 2012 to resolve O + , OH + , H 2 O + , and H 3 O + and to characterize their plasma properties, including number density, temperature, and thermodynamic κ. Our results demonstrate that O + is the dominant thermal ion species throughout Saturn's magnetosphere, comprising up to ∼70% of the total ion population beyond ∼5 Saturn radii (R S ). In contrast, molecular ions such as OH + , H 2 O + , and H 3 O + dominate closer to Enceladus but rapidly dissociate into atomic ions between ∼5 and 10 R S . This radial region is also characterized by the steepest increase in plasma flow speed, which rises from ∼40% to ∼80% of rigid corotation. Simultaneously, ion velocity distributions approach Maxwell–Boltzmann equilibrium, as indicated by high kappa values. These findings provide new constraints on the ion–neutral chemistry that regulates the balance between molecular and atomic ions in Saturn's magnetosphere. They also emphasize the critical role of the 5–10 R S region as a transition zone for both plasma composition and dynamics. Our results refine previous CAPS-based studies and underscore the need to incorporate seasonal variability and ionospheric coupling into future global models of Saturn's plasma environment.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗