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All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Tuning Uranium Redox Chemistry in Asymmetric Polyoxometalate Complexes: Access to U(IV), U(V), and Transient U(VI)

We report the synthesis and characterization of asymmetric sandwich-type complexes [TpU IV EW 11 O 39 ] x– (E = P; x = 4, E = Si; x = 5, Tp = trispyrazolylborate). These complexes represent rare examples of the selective formation of asymmetric actinide-polyoxometalate (An-POM) complexes. Oxidation studies show that the U V analogues are stable and accessible, with both complexes isolated. Attempts to access U VI with this framework yield mixed results. Attempts to produce [TpU VI PW 11 O 39 ] 2– only led to decomposition, while electrochemical oxidation experiments gave evidence of transient formation of [TpU VI SiW 11 O 39 ] 3– in solution. Rapid decomposition of [TpU VI SiW 11 O 39 ] 3– inhibits full characterization. These studies indicate that the redox properties and stability of An-POM complexes containing actinides in higher valencies are dependent on the anionic charge of the assembly.

Actinides↗
NASA NTRS2001

High-Pressure Synthesis of Metal-Ceramic Nano-Composites

The major problems in fabrication of nano-crystal line materials form nano-powders are: (1), coarsening of the initial nano-size grains, (2), insufficient densification (high concentration of pores), and, (3), conversion of diamond into graphite (for diamond-based ceramics). We have developed a novel technique of the synthesis of nano-composite materials applying very high (up to about 10 GPa) pressures. In this technique, one component is pre-compacted and placed next to another having a lower melting point temperature. The whole sample is pressed and the temperature raised above the melting point of the second component, what results in the melt getting pressed into the (nano-size) pores of the compact. Upon subsequent crystallization the melt forms the second nanophase. The process is fast, on the order of seconds, and the temperatures are relatively low what prevents, or at least significantly reduces coarsening of the starting nanophase grains. Also, conversion of diamond into graphite can be prevented. The technique allows for control of the final product properties through a proper selection of (1) the initial compact density and grain size, (2) chemical composition of the source, and (3) the temperature and pressure of the process. The application of the technique to the synthesis of SiC and diamond with Si, Ge, and different metals. Results of the in-situ investigation of the synthesis process by synchrotron X-ray diffraction technique will be presented.

Gierlotka, S.↗
NASA NTRS2002

The Evolution of Disks and Winds in Dwarf Nova Outbursts - FUSE

This project was a project to study the FUV spectra of two proto-typical dwarf novae, U Gem and SS Cygni, through an outburst cycle. The luminosity of the boundary layer in the two systems, as evidenced by earlier EUVE observations, is different in the two systems. Our intensive study of the two systems was intended to (1) probe the ionization and kinematic structure of the wind as a function of system brightness, (2) isolate the contributions of the disk to the FUV spectra, and (3) examine physical conditions and abundances of material just being accreted onto the disk from the secondary. The U Gem and SS Cyg observations took place in March and October 2000, respectively. The data obtained with FUSE was of excellent quality. Analysis of the both observations is now essentially complete, although some modeling of the SS Cyg spectra is ongoing, as we complete an ApJ manuscript on this object. Our main results for U Gem are as follows: The plateau spectra have continuum shapes and fluxes that are approximated by steady state accretion disk model spectra with an accretion rate 7x10(exp 9) Msolar/yr. The spectra also show numerous absorption lines of H I, He II, and 2-5 times ionized transitions of C, N, O, P, S, and Si. There are no emission features in the spectra, with the possible exception of a weak feature on the red wing of the 0 VI doublet. The absorption lines are narrow (FWHM approx. 50 km/s), too narrow to arise from the disk photosphere, and at low velocities (less than or equal to 700 km/s). The S VI and O VI doublets are optically thick. The absorption lines in the plateau spectra show orbital variability: in spectra obtained at orbital phases between 0.53 and 0.79, low-ionization absorption lines appear and the central depths of the preexisting lines increase. The increase in line absorption occurs at the same orbital phases as previously observed EUV and X-ray light-curve dips. If the absorbing material is in (near-) Keplerian rotation around the disk, it must be located at large disk radii. The final observation occurred when U Gem was about 2 mag from optical quiescence. The spectra are dominated by emission from an approx. 43,000 K, metal-enriched white dwarf (WD). The inferred radius of the WD is 4.95x10(exp 8) cm, close to that observed in quiescence. Allowing for a hot heated region on the surface of the WD improves the fit to the spectrum at short (less than 960 A) wavelengths. Our main results for SS Cyg are as follows: The first two of four observations of SS Cyg show disk dominated spectra with accretion rates of order 10(exp -8) Msolar/yr. Except for narrow interstellar features (atomic and molecular H), the lines are all broad consistent with a disk or wind origin. The O VI line in the spectra is mostly of wind origin as detailed modeling with our Monte Carlo code (developed in part using funds from this project) show. The continua from spectra in observations 3 and 4, observed during the decline phase, are not well fit with steady-state disks, and show considerable resemblance to quiescent spectra obtained with HUT. The most probable interpretation for the emission features seen in the spectrum in the last two observations is that they arise from a photo-illuminated choronosphere above the disk, rather than a wind.

Long, Knox↗
DOE OSTI2020

Materials Data on K2U(Si2O5)3 by Materials Project

K2U(Si2O5)3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 8-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.80–3.32 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.72–3.28 Å. In the third K1+ site, K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.88–3.41 Å. In the fourth K1+ site, K1+ is bonded to eight O2- atoms to form distorted KO8 hexagonal bipyramids that share corners with six SiO4 tetrahedra, edges with two equivalent UO6 octahedra, and edges with three SiO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.93–3.33 Å. There are two inequivalent U4+ sites. In the first U4+ site, U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 2.22–2.32 Å. In the second U4+ site, U4+ is bonded to six O2- atoms to form distorted UO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent KO8 hexagonal bipyramids. There are a spread of U–O bond distances ranging from 2.24–2.34 Å. There are twelve inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 47°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid, a cornercorner with one UO6 octahedra, and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent KO8 hexagonal bipyramids, a cornercorner with one UO6 octahedra, and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 26°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 39°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the seventh Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid, a cornercorner with one UO6 octahedra, and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the eighth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the ninth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 46°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the tenth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid, a cornercorner with one UO6 octahedra, and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the eleventh Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid, a cornercorner with one UO6 octahedra, and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the twelfth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 39°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are thirty inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one U4+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, one U4+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one U4+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the sixteenth O2- site, O2- is bonded in a 2-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the seventeenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the eighteenth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one U4+, and one Si4+ atom. In the nineteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the twentieth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the twenty-first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms. In the twenty-second O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the twenty-third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the twenty-fourth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the twenty-fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms. In the twenty-sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one U4+, and one Si4+ atom. In the twenty-eighth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the twenty-ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms. In the thirtieth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+ and two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Using an Absolute Cavity Pyrgeometer to Validate the Calibration of a Secondary Standard Pyrgeometer Outdoors, Independent from the Reference Value of the Atmospheric Longwave Irradiance

Accurate measurements of broadband outdoor longwave irradiance are important for renewable energy applications and the study of the atmosphere and climate change. A unique method of pyrgeometer calibration has been developed to improve the measurement uncertainty [1]. The results of this method yielded irradiance values within ±3 W/m 2 of those traceable to the World InfraRed Standard Group (WISG). This article describes a technique for validating this pyrgeometer calibration method using two Absolute Cavity Pyrgeometers (ACPs). The ACPs and pyrgeometer model PIR were deployed outdoors and the irradiance measured by the PIR was compared against the average irradiance measured by the two ACPs. The irradiance measured by the PIR was calculated using two equations, NREL equation and the Physikalisch Meteorologisches Observatorium Davos (PMOD) equation. The uncertainty with 95% confidence level ( U 95 ) of the irradiance measured by the PIR using NREL equation equaled ±3.51 W/m 2 with respect to SI and using PMOD equation U 95 equaled ±2.99 W/m 2 with respect to SI. These results suggest that the PIR calibration method might be useful in addressing the international need for a secondary standard pyrgeometer traceable to SI.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on K2U(Si2O5)3 by Materials Project

K2U(Si2O5)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.91–3.46 Å. In the second K1+ site, K1+ is bonded in a 3-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.80–3.46 Å. U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 2.21–2.30 Å. There are six inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 28°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 34°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one U4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one U4+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one U4+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one U4+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one U4+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2U(Si2O5)3 by Materials Project

Rb2U(Si2O5)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Rb–O bond distances ranging from 3.03–3.41 Å. In the second Rb1+ site, Rb1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Rb–O bond distances ranging from 2.94–3.45 Å. U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 2.22–2.28 Å. There are six inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 24°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 29°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two Rb1+, one U4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Rb1+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Rb1+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two Rb1+, one U4+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one U4+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one U4+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Rb1+ and two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one U4+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+, one U4+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2012

Chemical Mapping of Vesta and Ceres

Following successful science operations at Vesta, the Dawn spacecraft is headed for an encounter with Ceres in 2015. What have we learned at Vesta? And, what do we expect to learn by comparing Vesta and Ceres? We will address these questions from the standpoint of geochemistry. Dawn's Gamma Ray and Neutron Detector (GRaND) is sensitive to the elemental composition of surface materials to depths of a few decimeters [1]. Gamma rays and neutrons, produced by the steady bombardment of galactic cosmic rays and by the decay of naturally ]occurring radioisotopes (K, Th, U), provide a chemical fingerprint of the regolith. Analysis of planetary radiation emissions enables mapping of specific elements (such as Fe, Mg, Si, Cl, and H) and compositional parameters (such as average atomic mass), which provide information about processes that shaped the planet1s surface and interior. Dawn has exceeded operational goals for GRaND at Vesta, accumulating an abundance of nadir-pointed data during five months in a 210 km, low altitude mapping orbit around Vesta (265-km mean radius). Chemical information from gamma ray and neutron measurements was used to test the connection between Vesta and the howardite, eucrite, and diogenite (HED) meteorites [2]. Additionally, GRaND searched for evolved, igneous lithologies [3], mantle and upper crustal materials exposed in large impact basins, mesosiderite compositions, and hydrogen in Vesta1s bulk regolith. Results of our analyses and their implications for thermal evolution and regolith-processes will be presented. The possibility of a subcrustal ocean [4, 5] and lack of cerean meteorites makes water-rich Ceres a compelling target of exploration [6]. If Ceres underwent aqueous differentiation, then crustal overturn or gas driven volcanism may have significantly modified its primitive surface; and products of aqueous alteration (e.g. [7]) would detectable by GRaND [1]. For example, the presence of Cl in salts, associated with liquid-water-processes, would have a profound effect on the thermal neutron leakage flux. GRaND is sensitive to H and H-layering, which may be in the form of endogenic water ice or hydrous minerals on Ceres. Ammonia ice (e.g., from recent cryovolcanism) would produce a distinctly different neutron signature than water ice [1]. Prospective results for GRaND at Ceres will be presented in the context of what we have learned about Vesta.

Prettyman, Thomas H.↗
DOE OSTI2022

CLASSY IV. Exploring UV Diagnostics of the Interstellar Medium in Local High- z Analogs at the Dawn of the JWST Era

The Cosmic Origins Spectrograph (COS) Legacy Archive Spectroscopic SurveY (CLASSY) provides the first high resolution spectral catalog of 45 local high-z analogs in the ultraviolet (UV; 1200–2000 Å) to investigate their stellar and gas properties. Here we present a toolkit of UV interstellar medium (ISM) diagnostics, analyzing the main emission lines of CLASSY spectra (N IV] λλ1483,87, C IV λλ1548,51, He IIλ1640, O III]λλ1661,6, Si III] λλ1883,92, C III] λ1907,9). Specifically, our aim is to provide accurate diagnostics for the reddening E(B - V), electron density n e , electron temperature T e , metallicity 12+log(O/H), and ionization parameter log(U), taking the different ISM ionization zones into account. We calibrate our UV toolkit using well-known optical diagnostics, analyzing archival optical spectra for all CLASSY targets. We find that UV density diagnostics estimate n e values that are ~1–2 dex higher (e.g., n e (C III] λλ1907,9) ~ 10 4 cm -3 ) than those inferred from their optical counterparts (e.g., n e ([S II]λλ6717,31) ~ 10 2 cm -3 ; n e ([Ar IV]λλ4714,41) ~ 10 3 cm -3 ). T e derived from the hybrid ratio [O III] λ1666/λ5007 proves to be reliable, implying differences in determining 12+log(O/H) compared to the optical counterpart O III] λ4363/[O III] λ5007 within ~ ±0.3 dex. We also investigate the relation between the stellar and gas E(B - V), finding consistent values at high specific star formation rates (sSFRs; log sSFR ≳ -8 yr -1 ), while at low sSFRs we confirmed an excess of dust attenuation in the gas. Finally, we investigate UV line ratios and equivalent widths to provide correlations with 12+log (O/H) and log(U), but note that there are degeneracies between the two. With this suite of UV-based diagnostics, we illustrate the pivotal role CLASSY plays in understanding the chemical and physical properties of high-z systems that JWST can observe in the rest-frame UV.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on Cs2U(Si2O5)3 by Materials Project

Cs2U(Si2O5)3 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Cs–O bond distances ranging from 3.32–3.71 Å. In the second Cs1+ site, Cs1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Cs–O bond distances ranging from 3.23–3.44 Å. U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 2.24–2.28 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 33°. There are a spread of Si–O bond distances ranging from 1.60–1.64 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 34°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one UO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 29°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Cs1+, one U4+, and one Si4+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Si4+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Cs1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two Cs1+, one U4+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+ and two equivalent Si4+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one U4+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cs1+ and two equivalent Si4+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cs1+ and two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Diastereoselective Template Synthesis on Iron and Uranium

The addition of 2 equiv of t Bu 2 PSiMe 3 to 2,6-pyridinedicarboxaldehyde ((CHO) 2 Py) results in a rac / meso diastereomeric mixture of the PNP-chelating ligand 2,6-bis((trimethylsiloxy)(di- tert -butylphosphino)-methyl)-pyridine ( (OTMS) PNP t Bu ) ( 1 - r / m ) via addition of the P–Si bond across both of the aldehyde C–O bonds. Chelation of (OTMS) PNP t Bu to FeCl 2 results in the same diastereotopic ratio of ( (OTMS) PNP t Bu )FeCl 2 ( 2- r / m ) as the free ligand. Fractional crystallization allows for the isolation of the C 2 isomer, 2- r , and a template synthesis protocol allows for the synthesis and isolation of the C s isomer, 2- m , in good yield. Furthermore, the template synthesis protocol was also expanded to the f -block with the use of UCl 4 in order to assess the specificity of the template synthesis on a larger metal cation. This reaction performed on UCl 4 forms the meso diastereospecific uranium complex ( ( t Bu2P) ONO)UCl 2 (dtbpy), 3 - m , with observation of the rational intermediate ( (OTMS) PNO t Bu )UCl 3 (dtbpy), 4 - m , which arose from the respective formation of two- or one-equivalents of TMS–Cl and formation of the corresponding U–O bond.

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

Materials Data on CaU2Si2(HO3)4 by Materials Project

CaU2Si2(HO3)4 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to two H1+ and four O2- atoms. There are one shorter (2.49 Å) and one longer (2.58 Å) Ca–H bond lengths. There are a spread of Ca–O bond distances ranging from 2.18–2.58 Å. There are two inequivalent U5+ sites. In the first U5+ site, U5+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with three equivalent SiO4 tetrahedra, edges with two equivalent UO7 pentagonal bipyramids, and an edgeedge with one SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.83–2.55 Å. In the second U5+ site, U5+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with three equivalent SiO4 tetrahedra, edges with two equivalent UO7 pentagonal bipyramids, and an edgeedge with one SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.80–2.55 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent UO7 pentagonal bipyramids and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of Si–O bond distances ranging from 1.61–1.72 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent UO7 pentagonal bipyramids and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of Si–O bond distances ranging from 1.57–1.73 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one Ca2+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one Ca2+ atom. In the third 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 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 twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one U5+, one Si4+, and one H1+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Ca2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent U5+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent U5+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one U5+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Si4+, and one H1+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one U5+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one U5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and one U5+ atom. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent U5+ and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Ca2+ and one U5+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent U5+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Laser Plasma Interaction in the MG Magnetic Field (Final Report)

Strong magnetic fields change properties of plasma. Employment of the magnetic fields can improve conditions for inertial confinement fusion. Compression and heating of the magnetized plasma is a base of the MagLIF pulsed power approach to the controlled fusion. Study of expansion and heating of plasma in the external magnetic fields, development of plasma instabilities, parametric and other effects are important for basic physics and applications. The main goal of the research for the grant was experimental investigation of laser produced plasma in the well characterized and controlled MG magnetic fields. We developed a platform for investigation of high intensity laser-plasma interaction (LPI) in the MG fields using a university-scale pulsed power machine. A Zebra machine at UNR generated transverse magnetic fields of 3 MG on the surface of the rod load and longitudinal fields of 1.4 MG in the coil loads. The magnetic fields were characterized with two-color Faraday rotation diagnostics. The pulsed power machine provided almost static magnetic fields for LPI compared to the much faster laser driven magnetic fields. We found that eddy currents in the rising magnetic field generate plasma on the metal targets. Eddy currents did not impact Si and CH dielectric targets. A Leopard laser with intensity in the focus up to 10 19 W/cm 2 produced plasma in the MG magnetic fields. The modified reflected Faraday diagnostics was used to study laser driven B-field at the MTW laser at Laboratory for Laser Energetics, UR. We demonstrated a slow dependence of the magnetic field in the coil on the applied laser intensity. The magnetic field increased by a factor of 2 if laser intensity increased by a factor of 30. This scaling is important for comparison of experiments at different laser facilities. Expansion of the plasma in the 2-3 MG external B-field was studied. Laser-produced plasma in the azimuthal magnetic field took the unique form of a thin disc expanding radially with a velocity of 250 km/s and confined in the vertical direction. A HYDRA MHD program at the University of Rochester was applied for simulations of LPI in the magnetic field B >3 MG. Simulations for the plasma disc parameters and the expansion dynamics were in a good agreement with experiments. Generation of narrow dense plasma jets in the longitudinal magnetic field of 0.6-0.8 MG was studied. Narrow plasma jets reached a length of 3-4 mm with the electron plasma density of (0.2-1.2)x10 20 cm -3 . A jet tip propagated with the velocity of 160-200 km/s. MHD simulations showed a good agreement of the dynamics of the formation of plasma jets with experiments. These jets are relevant to astrophysical jets. Simulations of K-shell spectra of Si plasma was performed for LPI in the B-field. The laser prepulse generated plasma near the laser target. A PrismSPECT model with a MeV electron beam produced by the laser was used. The spectral modelling showed the increased plasma density by a factor by 2-3 in the magnetic field. This was in agreement with the observed dynamics of the plasma plume confined by the axial magnetic field. The two-plasmon decay was studied in the 2.5-3 MG transversal magnetic fields. Strong 2-3.5 nm spectral widening and a 2-4 nm shifts of “red” and “blue” 3/2ω 0 spectral components were observed. The large shift and widening exceed the expected temperature and magnetic shift. PIC simulations are performing to clarify physics of this effect. The experimental research program for the grant is completed. New plasma effects in the MG fields were studied at the university-scale pulsed power generator. Two graduate and two undergraduate UNR and UR students carried experiments at the Zebra generator, supported and developed plasma diagnostics, provided data processing, and performed MHD simulations of LPI in the strong magnetic field. Research results are published in 9 referred papers and presented in 12 conferences. Program manager: Kramer U. Akli; Collaborators: R. C. Mancini and H. Sawada, University of Nevada, Reno (UNR); R. Betti and A. V. Maximov, University of Rochester (UR).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Mechanical Design Progress of the In Situ Nanoprobe Instrument for APS-U

The In Situ Nanoprobe (ISN, 19-ID) beamline will be a new best-in-class long beamline to be constructed as part of the Advanced Photon Source Upgrade (APS-U) project [1, 2]. To achieve long working distance at high spatial resolution, the ISN instrument will be positioned 210 m downstream of the x-ray source, in a dedicated satellite building, currently under construction [3]. The ISN instrument will use a nano-focusing Kirkpatrick-Baez (K-B) mirror system, which will focus hard x-rays to a focal spot as small as 20 nm, with a large working distance of 61 mm. The large working distance provides space for various in situ sample cells for x-ray fluorescence tomography and ptychographic 3D imaging, allows the use of a separate, independent vacuum chambers for the optics and sample, and provides the flexibility to run experiments in vacuum or at ambient pressure. A consequence of the small spot size and large working distance are stringent requirements for high angular stability of the K-B mirrors (5 nrad V-mirror and 16 nrad H-mirror) and high relative stability be-tween focus spot and sample (4 nmRMS). Additional features include fly-scanning up to 2 kg mass, sample plus in situ cell, at 1 mm/s in vertical and/or horizontal directions over an area of 10 mm x 10 mm. Environmental capabili-ties will include heating and cooling, flow of fluids and applied fields, as required for electrochemistry and flow of gases at high temperature for catalysis. To achieve these capabilities and precise requirements we have used precision engineering fundamentals to guide the design process.

Kearney, Steven P.↗
DOE OSTI2021

Cryo-EM model validation recommendations based on outcomes of the 2019 EMDataResource challenge

This paper describes outcomes of the 2019 Cryo-EM Model Challenge. The goals were to (1) assess the quality of models that can be produced from cryogenic electron microscopy (cryo-EM) maps using current modeling software, (2) evaluate reproducibility of modeling results from different software developers and users and (3) compare performance of current metrics used for model evaluation, particularly Fit-to-Map metrics, with focus on near-atomic resolution. Our findings demonstrate the relatively high accuracy and reproducibility of cryo-EM models derived by 13 participating teams from four benchmark maps, including three forming a resolution series (1.8 to 3.1 Å). The results permit specific recommendations to be made about validating near-atomic cryo-EM structures both in the context of individual experiments and structure data archives such as the Protein Data Bank. We recommend the adoption of multiple scoring parameters to provide full and objective annotation and assessment of the model, reflective of the observed cryo-EM map density.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Materials Data on CaU2Si2(HO3)4 by Materials Project

(CaU2Si2(HO4)3)2H2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four hydrogen molecules and one CaU2Si2(HO4)3 framework. In the CaU2Si2(HO4)3 framework, Ca2+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Ca–O bond distances ranging from 2.15–2.33 Å. There are two inequivalent U5+ sites. In the first U5+ site, U5+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with three SiO4 tetrahedra, edges with two equivalent UO7 pentagonal bipyramids, and an edgeedge with one SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.83–2.60 Å. In the second U5+ site, U5+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with three SiO4 tetrahedra, edges with two equivalent UO7 pentagonal bipyramids, and an edgeedge with one SiO4 tetrahedra. There are a spread of U–O bond distances ranging from 1.86–2.54 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three UO7 pentagonal bipyramids and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of Si–O bond distances ranging from 1.62–1.69 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three UO7 pentagonal bipyramids and an edgeedge with one UO7 pentagonal bipyramid. There are a spread of Si–O bond distances ranging from 1.58–1.73 Å. There are three 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 0.97 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Ca2+ and one U5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one U5+, one Si4+, and one H1+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one U5+, one Si4+, and one H1+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two U5+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Ca2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two U5+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two U5+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one U5+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to two U5+ and one Si4+ atom. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Ca2+ and one U5+ atom. In the eleventh O2- site, O2- is bonded in a bent 120 degrees geometry to one Si4+ and one H1+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Ca2+ and one U5+ atom.

36 MATERIALS SCIENCE↗