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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Mg3P2(HO)16 by Materials Project

Mg3P2(HO)16 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Mg3P2(HO)16 sheets oriented in the (0, 1, 0) direction. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent PO4 tetrahedra. There are two shorter (2.06 Å) and four longer (2.14 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with four equivalent PO4 tetrahedra and an edgeedge with one MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.16 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with five MgO6 octahedra. The corner-sharing octahedra tilt angles range from 46–56°. There are a spread of P–O bond distances ranging from 1.55–1.58 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.73 Å) H–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Mg2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Mg2+ and two H1+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Mg2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Mg2+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Mg2+, one P5+, and two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Collision strengths for 1199 and 1729 of S III

Collision strengths are calculated for the S III ground state from electron impact excitation in the Io torus. The study is based on data taken at 119.9 nm and 172.9 nm by the IUE spacecraft and with the rocket-borne Faint Object Telescope. The collision strengths of the 3p(2)3P3s3p(3)(5)S(4) and (3)P-3s3p(3)(3)D(0) UV lines are derived from a three-state close coupling aproximation. A Gailitis averaging scheme accounts for resonance effects in the forbidden transition. The calculated intensities of the two transitions at an electron temperature of 80,000 K are in agreement with observed intensities.

Ho, Y. K.↗
NASA NTRS1993

A new observational and numerical study of tidal interactions in M81-M82-NGC3077 system

A nearby system of interacting galaxies M81-M82-NGC3077 triplet (D = 3.3 Mpc; Freeman & Madore 1988) has been studied using multi-wavelength observations and numerical simulations to obtain a comprehensive understanding on the dynamics and the consequences of tidal interactions in a group environment. The VLA 12-field Mosaic H I observations of 2 x 1.5 deg. region have revealed a vast array of H I filaments which suggests that the severity and extent of tidal disruptions far exceed the previous estimates. A tidal remnant of the former H I disk of M82 extending up to 30 kpc (in projection) is identified for the first time, and the pervasive effects of the tidal disruption are traced into the inner disk by optical and CO observations, including a kinematic trace of a large scale bar potential (Yun, Ho, & Lo 1992). The H I disk of M81 is traced out to 40 kpc in radius, and a large scale (l approx. 20 kpc) velocity anomaly ('High Velocity Trough'), which may be a remnant of a gaseous collision, is found within the disk of M81. The large H I bridge between M81 and NGC 3077 (van der Hulst 1979) is also found to extend approx. greater than 50 kpc further, bending around NGC 3077, toward M82. The total H I detected in this experiment, 5.6 x 10(exp 9) solar mass, represents the majority of the single-dish flux (Appleton, Davies, & Stephenson 1981) and suggests that the bulk of H I found in the region belongs to the three galaxies and the tidal filaments. The impact and details of the tidal interactions have been further examined through the use of numerical techniques. The 'restricted 3-body' approach was used to simulate the observed distribution of tidal H I streamers connecting the three galaxies, and the success of the simulation is further strengthened by the accurate predictions on the gas kinematics.

Yun, M. S.↗
DOE OSTI2022

Insights on the corrosion thermodynamics of chromium in molten LiF-NaF-KF eutectic salts

The thermodynamic stability of chromium in the Cr 0 , Cr 2+ , and Cr 3+ oxidation states considering various F - ion coordination compounds was investigated in molten LiF–NaF-KF (FLiNaK) eutectic salt. Potential fluoride ion activity (F - and CrF 3 - ) diagrams were constructed to predict the most stable Cr oxidation states as a function of anion activity, solvation state of chromium ions and potential at 600 °C. The Gibbs free energies of these compounds were estimated by utilizing a combined cyclic voltammetry – Nernst theory analysis approach in FLiNaK salt. To verify the constructed diagrams, X-ray diffraction was utilized after exposure of Cr at various applied potentials to determine whether compounds detected in solidified FLiNaK salts agreed with thermodynamic calculations. This work aims to identify key thermodynamic factors that are significant to chromium corrosion for molten salt nuclear reactor applications. The F - stability region spans the entire region where spontaneous corrosion of Cr occurs. Cr may be oxidized to Cr 2+ and Cr 3+ in the presence HF (due to moisture as an impurity) spontaneously except some conditions of p 1/2 H 2 /a HF etc. This situation is not changed qualitatively for various states of solvation between oxidized Cr solute in F - solvent and this aspect is substantially similar for the two cases (pair 1: Cr 0 /CrF 3 - / CrF 6 3- ; pair 2: Cr 0 /CrF 4 2- /CrF 5 2- ) considered in this work.

36 MATERIALS SCIENCE↗
NASA NTRS2019

Machine Learning, Markov Chain Monte Carlo, and Optimal Algorithms to Characterize the AdvACT Kilopixel Transition-Edge Sensor Arrays

Next-generation focal planes comprising dozens of kilopixel transition-edge sensor (TES) arrays require new methods to rapidly screen candidate arrays, evaluate array non-idealities in the field, identify outlier devices for removal, and optimize the array performance in the field. We demonstrate robust methods to estimate TES parameters (critical temperatures and thermal conductivity parameters) and their uncertainties using a custom Markov Chain Monte Carlo (MCMC) algorithm. We also constrain systematic effects in estimating the TES parameters from non-isothermal current-voltage curves (IVs) at approximately a ~3% level. Additionally, for the first time, we have applied Machine Learning (ML) algorithms to tune detector arrays and optimize their performance.

Maria Salatino↗
DOE OSTI2020

Materials Data on Ho2CoTe2(SO7)2 by Materials Project

Ho2CoTe2(SO7)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.26–2.57 Å. Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent SO4 tetrahedra. There are a spread of Co–O bond distances ranging from 2.05–2.13 Å. Te4+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Te–O bond distances ranging from 1.90–1.92 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share a cornercorner with one CoO6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are a spread of S–O bond distances ranging from 1.48–1.51 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Ho3+ and one S6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Co2+ and one S6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ho3+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ho3+ and one S6+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ho3+ and one Te4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ho3+, one Co2+, and one Te4+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+, one Co2+, and one Te4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mechanoadaptive strain and functional osseointegration of dental implants in rats

Spatiotemporal implant-bone biomechanics and mechanoadaptive strains in peri-implant tissue are poorly understood. Physical and chemical characteristics of an implant-bone complex (IBC) were correlated in three-dimensional space (along the length and around a dental implant) to gather insights into time related integration of the implant with the cortical portion of a jaw bone in a rat. Rats (N = 9) were divided into three experimental groups with three rats per time point; 3-, 11-, and 24-day. All rats were fed crumbled hard pellets mixed with water (soft-food diet) for the first 3 days followed by a hard-food diet with intact hard-food pellets (groups of 11- and 24-day only). Biomechanics of the IBCs harvested from rats at each time point was evaluated by performing mechanical testing in situ in tandem with X-ray imaging. The effect of physical association (contact area) of a loaded implant with adapting peri-implant tissue, and resulting strain within was mapped by using digital volume correlation (DVC) technique. The IBC stiffness at respective time points was correlated with mechanical strain in peri-implant tissue. Results illustrated that IBC stiffness at 11-day was lower than that observed at 3-day. However, at 24-day, IBC stiffness recovered to that which was observed at 3-day. Furthermore, correlative microscopy and spectroscopy illustrated that the lower IBC stiffness was constituted by softer and less mineralized peri-implant tissue that contained varying expressions of osteoconductive elements. Lower IBC stiffness observed at 11-day was constituted by less mineralized peri-implant tissue with osteoconductive elements that included phosphorus (P) which was co-localized with higher expression of zinc (Zn), and lower expression of calcium (Ca). Higher IBC stiffness at 24-day was constituted by mineralized peri-implant tissue with higher expressions of osteoconductive elements including Ca and P, and lower expressions of Zn. These spatiotemporal correlative maps of peri-implant tissue architecture, heterogeneous distribution of mineral density, and elemental colocalization underscore mechanoadaptive physicochemical properties of peri-implant tissue that facilitate functional osseointegration of an implant. These results provided insights into 1) plausible "prescription" of mechanical loads as an osteoinductive "therapeutic dose" to encourage osteoconductive elements in the peri-implant tissue that would facilitate functional osseointegration of the implant; 2) a "critical temporal window" between 3 and 11 days, and perhaps it is this acute phase during which key candidate regenerative molecules can be harnessed to accelerate osseointegration of an implant under load.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2013

Einstein@Home All-Sky Search for Periodic Gravitational Waves in LIGO S5 Data

This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50, 1 190] Hzand and with frequency derivative range of approx. [-20,1.1] x 10(exp-10) H(sub 0)z s(exp-1) for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we report upper limits on the intrinsic gravitational wave strain amplitude ho. For example, in the 0.5 Hz-wide band at 152.5 Hz, we can exclude the presence of signals with h(exp 0) greater than 7.6 x 10(exp-25) at a 90% confidence level. This search is about a factor 3 more sensitive than the previous Einstein@Home search of early S5 LIGO data.

J Aasi↗
DOE OSTI2020

Materials Data on MgP(HO)7 by Materials Project

MgP(HO)7 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent PO4 tetrahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.17 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent MgO6 octahedra. The corner-sharing octahedra tilt angles range from 13–44°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. There are seven inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the fourth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.02 Å) and one longer (1.56 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one P5+ and one H1+ atom. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Mg2+ and two H1+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Mg2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to one Mg2+ and two H1+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one P5+, and one H1+ atom. In the sixth O2- site, O2- is bonded in a distorted water-like geometry to one Mg2+ and two H1+ atoms. In the seventh O2- site, O2- is bonded in a linear geometry to one Mg2+ and one P5+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Predicting survival in heart failure case and control subjects by use of fully automated methods for deriving nonlinear and conventional indices of heart rate dynamics

BACKGROUND: Despite much recent interest in quantification of heart rate variability (HRV), the prognostic value of conventional measures of HRV and of newer indices based on nonlinear dynamics is not universally accepted. METHODS AND RESULTS: We have designed algorithms for analyzing ambulatory ECG recordings and measuring HRV without human intervention, using robust methods for obtaining time-domain measures (mean and SD of heart rate), frequency-domain measures (power in the bands of 0.001 to 0.01 Hz [VLF], 0.01 to 0.15 Hz [LF], and 0.15 to 0.5 Hz [HF] and total spectral power [TP] over all three of these bands), and measures based on nonlinear dynamics (approximate entropy [ApEn], a measure of complexity, and detrended fluctuation analysis [DFA], a measure of long-term correlations). The study population consisted of chronic congestive heart failure (CHF) case patients and sex- and age-matched control subjects in the Framingham Heart Study. After exclusion of technically inadequate studies and those with atrial fibrillation, we used these algorithms to study HRV in 2-hour ambulatory ECG recordings of 69 participants (mean age, 71.7+/-8.1 years). By use of separate Cox proportional-hazards models, the conventional measures SD (P<.01), LF (P<.01), VLF (P<.05), and TP (P<.01) and the nonlinear measure DFA (P<.05) were predictors of survival over a mean follow-up period of 1.9 years; other measures, including ApEn (P>.3), were not. In multivariable models, DFA was of borderline predictive significance (P=.06) after adjustment for the diagnosis of CHF and SD. CONCLUSIONS: These results demonstrate that HRV analysis of ambulatory ECG recordings based on fully automated methods can have prognostic value in a population-based study and that nonlinear HRV indices may contribute prognostic value to complement traditional HRV measures.

Non-NASA Center↗
DOE OSTI2020

Materials Data on YbP3(HO)6 by Materials Project

Yb(H2PO2)3 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Yb(H2PO2)3 sheets oriented in the (1, 0, 0) direction. there are two inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded to six O2- atoms to form YbO6 octahedra that share corners with six PH2O2 tetrahedra. There are two shorter (2.31 Å) and four longer (2.32 Å) Yb–O bond lengths. In the second Yb3+ site, Yb3+ is bonded to six O2- atoms to form YbO6 octahedra that share corners with six PH2O2 tetrahedra. There are four shorter (2.30 Å) and two longer (2.33 Å) Yb–O bond lengths. There are three inequivalent P+2.33+ sites. In the first P+2.33+ site, P+2.33+ is bonded to two H+0.33+ and two equivalent O2- atoms to form distorted PH2O2 tetrahedra that share corners with two equivalent YbO6 octahedra. The corner-sharing octahedral tilt angles are 32°. Both P–H bond lengths are 1.43 Å. Both P–O bond lengths are 1.52 Å. In the second P+2.33+ site, P+2.33+ is bonded to two H+0.33+ and two equivalent O2- atoms to form distorted PH2O2 tetrahedra that share corners with two equivalent YbO6 octahedra. The corner-sharing octahedral tilt angles are 27°. There is one shorter (1.42 Å) and one longer (1.43 Å) P–H bond length. Both P–O bond lengths are 1.52 Å. In the third P+2.33+ site, P+2.33+ is bonded to two equivalent H+0.33+ and two O2- atoms to form distorted PH2O2 tetrahedra that share corners with two YbO6 octahedra. The corner-sharing octahedra tilt angles range from 22–33°. Both P–H bond lengths are 1.43 Å. There is one shorter (1.51 Å) and one longer (1.52 Å) P–O bond length. There are five inequivalent H+0.33+ sites. In the first H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one P+2.33+ atom. In the second H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one P+2.33+ atom. In the third H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one P+2.33+ atom. In the fourth H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one P+2.33+ atom. In the fifth H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one P+2.33+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Yb3+ and one P+2.33+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Yb3+ and one P+2.33+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Yb3+ and one P+2.33+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Yb3+ and one P+2.33+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2022

The First Gradual Solar Energetic Particle Event With an Enhanced He-3 Abundance on Solar Orbiter

The origin of 3 He abundance enhancements in gradual solar energetic particle (SEP) events remains largely unexplained. Two mechanisms have been suggested: the reacceleration of remnant flare material by coronal mass ejection (CME)-driven shocks in interplanetary space, and concomitant activity in the corona. We explore the first gradual SEP event with enhanced 3 He abundance that was observed by Solar Orbiter. The event started on 2020 November 24 and was associated with a relatively fast halo CME. During the event, the spacecraft was at 0.9 au from the Sun. The event-averaged 3 He/ 4 He abundance ratio is 24 times higher than the coronal or solar wind value, and the timing of the 3He intensity was similar to that of other species. We inspected available imaging, radio observations, and the spacecraft magnetic connection to the CME source. The most probable cause of the enhanced 3He abundance apparently are residual 3He ions remaining from a preceding long period of 3 He-rich SEPs on 2020 November 17–23.

Solar particle emission↗
DOE OSTI2024

Effect of f -element complexation on the radiolysis of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])

A systematic study of the impact on the chemical reactivity of the oxidising n-dodecane radical cation (RH˙ + ) with f-element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP]) 2 ) 3 ], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in n-dodecane solvent, whose rate coefficient was k = (4.66 ± 0.22) × 10 9 M -1 s -1 . Similar reactivity enhancement was also observed for the corresponding americium ion complex, k = (5.58 ± 0.30) × 10 10 M -1 s -1 . The vastly increased reactivity of these f-element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. In conclusion, complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ~38% increase in ligand loss of a 1:1 [La((HEH[EHP]) 2 ) 3 ]: HEH[EHP] ratio system.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Inverse-Designed Photonics for Semiconductor Foundries

Silicon photonics is becoming a leading technology in photonics, displacing traditional fiber optic transceivers and enabling new applications. Further improving the density and performance of silicon photonics, however, has been challenging due to the large size and limited performance of traditional semianalytically designed components. Automated optimization of photonic devices using inverse design is a promising path forward but has, until now, faced difficulties in producing designs that can be fabricated reliably at scale. In this paper we experimentally demonstrate four inverse-designed devices made successfully in a commercial silicon photonics foundry: a spatial mode multiplexer, wavelength demultiplexer, 50–50 directional coupler, and 3-way power splitter. These devices are efficient, robust to fabrication variability, and compact, with footprints only a few micrometers across. They pave the way forward for the widespread practical use of inverse design.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co3P2(HO)16 by Materials Project

Co3P2(HO)16 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Co3P2(HO)16 sheets oriented in the (0, 1, 0) direction. there are two inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent PO4 tetrahedra. There are two shorter (2.08 Å) and four longer (2.16 Å) Co–O bond lengths. In the second Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four equivalent PO4 tetrahedra and an edgeedge with one CoO6 octahedra. There are a spread of Co–O bond distances ranging from 2.09–2.19 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with five CoO6 octahedra. The corner-sharing octahedra tilt angles range from 46–57°. There are a spread of P–O bond distances ranging from 1.55–1.58 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.74 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Co2+, one P5+, and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Co2+ and one P5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Co2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to one Co2+ and two H1+ atoms. In the fifth O2- site, O2- is bonded in a distorted water-like geometry to one Co2+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2000

High Energy Directly Pumped Ho:YLF Laser

The most commonly used crystal architecture to produce 2 micrometer laser is co-doping Ho and Tm into a single host crystal. In this method, the stored energy transfer from the Tm (3)F4 to the Ho (5)I7 manifold is not fast enough to warrant high efficiency for short pulse applications. By separating the Ho and the Tm ions and doping the Tm in YALO3 and the Ho in YLF, we were able to directly pump the Ho (5)I7 manifold with 1.94 micrometers. The Ho:YLF laser has produced 33 mJ at 2.062 micrometers with a quantum efficiency of 0.88. The performance of each laser will be presented.

Petros, Mulugeta↗
DOE OSTI2020

Materials Data on Ni3P2(HO)16 by Materials Project

Ni3P2(HO)16 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Ni3P2(HO)16 sheets oriented in the (0, 1, 0) direction. there are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with two equivalent PO4 tetrahedra. There are two shorter (2.06 Å) and four longer (2.12 Å) Ni–O bond lengths. In the second Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with four equivalent PO4 tetrahedra and an edgeedge with one NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 2.06–2.15 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with five NiO6 octahedra. The corner-sharing octahedra tilt angles range from 46–58°. There are a spread of P–O bond distances ranging from 1.55–1.58 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.70 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Ni2+, one P5+, and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ni2+ and one P5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Ni2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to one Ni2+ and two H1+ atoms. In the fifth O2- site, O2- is bonded in a distorted water-like geometry to one Ni2+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Lasing characteristics of ZrO{sub 2} − Y{sub 2}O{sub 3} − Ho{sub 2}O{sub 3} crystals pumped by a Tm : LiYF{sub 4} laser

Two-micron lasing is obtained on the {sup 5}I{sub 7} → {sup 5}I{sub 8} transition of Ho{sup 3+} ions in ZrO{sub 2} − Y{sub 2}O{sub 3} −Ho{sub 2}O{sub 3} crystals upon resonance pumping into the {sup 5}I{sub 7} level of these ions by a pulsed laser based on a Tm : LiYF{sub 4} crystal. The efficiency of conversion of pump radiation incident on the crystal to laser radiation and the slope lasing efficiency at a pulse duration of 8 ms and a pulse repetition rate of 10 Hz were 25% and 28%, respectively. (paper)

36 MATERIALS SCIENCE↗