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418 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Eu4PdO7 by Materials Project

Eu4PdO7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Eu3+ sites. In the first Eu3+ site, Eu3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Eu–O bond distances ranging from 2.31–2.61 Å. In the second Eu3+ site, Eu3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.28–2.89 Å. In the third Eu3+ site, Eu3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.35–2.80 Å. In the fourth Eu3+ site, Eu3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.31–2.66 Å. There are two inequivalent Pd2+ sites. In the first Pd2+ site, Pd2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.02 Å) and two longer (2.07 Å) Pd–O bond lengths. In the second Pd2+ site, Pd2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.03 Å) and two longer (2.07 Å) Pd–O bond lengths. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four Eu3+ and one Pd2+ atom to form distorted OEu4Pd square pyramids that share a cornercorner with one OEu4Pd square pyramid, corners with six OEu4 tetrahedra, an edgeedge with one OEu4Pd square pyramid, and edges with two equivalent OEu4 tetrahedra. In the second O2- site, O2- is bonded to four Eu3+ atoms to form OEu4 tetrahedra that share corners with three equivalent OEu4Pd square pyramids, corners with four OEu4 tetrahedra, and edges with three OEu4 tetrahedra. In the third O2- site, O2- is bonded in a 3-coordinate geometry to four Eu3+ atoms. In the fourth O2- site, O2- is bonded to four Eu3+ atoms to form OEu4 tetrahedra that share corners with four OEu4 tetrahedra, edges with two equivalent OEu4Pd square pyramids, and edges with two OEu4 tetrahedra. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to three Eu3+ and two Pd2+ atoms. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to four Eu3+ and one Pd2+ atom. In the seventh O2- site, O2- is bonded to four Eu3+ atoms to form OEu4 tetrahedra that share corners with three equivalent OEu4Pd square pyramids, corners with four OEu4 tetrahedra, and edges with three OEu4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm4PdO7 by Materials Project

Sm4PdO7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sm–O bond distances ranging from 2.31–2.57 Å. In the second Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.28–2.87 Å. In the third Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.33–2.76 Å. In the fourth Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.29–2.64 Å. There are two inequivalent Pd2+ sites. In the first Pd2+ site, Pd2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.05 Å) and two longer (2.07 Å) Pd–O bond lengths. In the second Pd2+ site, Pd2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.06 Å) and two longer (2.07 Å) Pd–O bond lengths. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four Sm3+ and one Pd2+ atom to form distorted OSm4Pd square pyramids that share a cornercorner with one OSm4Pd square pyramid, corners with six OSm4 tetrahedra, an edgeedge with one OSm4Pd square pyramid, edges with two equivalent OSm4 tetrahedra, and edges with two equivalent OSm4Pd trigonal bipyramids. In the second O2- site, O2- is bonded to four Sm3+ atoms to form OSm4 tetrahedra that share corners with three equivalent OSm4Pd square pyramids, corners with four OSm4 tetrahedra, corners with two equivalent OSm4Pd trigonal bipyramids, edges with three OSm4 tetrahedra, and an edgeedge with one OSm4Pd trigonal bipyramid. In the third O2- site, O2- is bonded in a 3-coordinate geometry to four Sm3+ atoms. In the fourth O2- site, O2- is bonded to four Sm3+ atoms to form OSm4 tetrahedra that share corners with four OSm4 tetrahedra, corners with two equivalent OSm4Pd trigonal bipyramids, edges with two equivalent OSm4Pd square pyramids, edges with two OSm4 tetrahedra, and an edgeedge with one OSm4Pd trigonal bipyramid. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to three Sm3+ and two Pd2+ atoms. In the sixth O2- site, O2- is bonded to four Sm3+ and one Pd2+ atom to form distorted OSm4Pd trigonal bipyramids that share corners with eight OSm4 tetrahedra, a cornercorner with one OSm4Pd trigonal bipyramid, edges with two equivalent OSm4Pd square pyramids, and edges with two OSm4 tetrahedra. In the seventh O2- site, O2- is bonded to four Sm3+ atoms to form OSm4 tetrahedra that share corners with three equivalent OSm4Pd square pyramids, corners with four OSm4 tetrahedra, corners with four equivalent OSm4Pd trigonal bipyramids, and edges with three OSm4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ferrotorryweiserite, Rh 5 Fe 10 S 16 , a New Mineral Species from the Sisim Placer Zone, Eastern Sayans, Russia, and the Torryweiserite–Ferrotorryweiserite Series

Ferrotorryweiserite, Rh 5 Fe 10 S 16 , occurs as small grains (≤20 µm) among droplet-like inclusions (up to 50 μm in diameter) of platinum-group minerals (PGM), in association with oberthürite or Rh-bearing pentlandite, laurite, and a Pt-Pd-Fe alloy (likely isoferroplatinum and Fe-Pd-enriched platinum), hosted by placer grains of Os-Ir alloy (≤0.5 mm) in the River Ko deposit. The latter is a part of the Sisim placer zone, which is likely derived from ultramafic units of the Lysanskiy layered complex, southern Krasnoyarskiy kray, Russia. The mineral is opaque, gray to brownish gray in reflected light, very weakly bireflectant, not pleochroic to weakly pleochroic (grayish to light brown tints), and weakly anisotropic. The calculated density is 5.93 g·cm –3 . Mean results (and ranges) of four WDS analyses are: Ir 18.68 (15.55–21.96), Rh 18.34 (16.32–20.32), Pt 0.64 (0.19–1.14), Ru 0.03 (0.00–0.13), Os 0.07 (0.02–0.17), Fe 14.14 (13.63–14.64), Ni 13.63 (12.58–14.66), Cu 4.97 (3.42–6.41), Co 0.09 (0.07–0.11), S 29.06 (28.48–29.44), and total 99.66 wt.%. They correspond to the following formula calculated for a total of 31 atoms per formula unit: (Rh 3.16 Ir 1.72 Pt 0.06 Ru 0.01 Os 0.01 ) Σ 4.95 (Fe 4.48 Ni 4.11 Cu 1.38 Co 0.03 ) Σ10.00 S 16.05 . The results of synchrotron micro-Laue diffraction studies indicate that ferrotorryweiserite is trigonal; its probable space group is $R\bar{3}m$ (#166) based on its Ni-analog, torryweiserite. The unit-cell parameters refined from 177 reflections are a = 7.069 (2) Å, c = 34.286 (11) Å, V = 1484 (1) Å 3 , and Z = 3. The c:a ratio is 4.8502. The strongest eight peaks in the X-ray diffraction pattern derived from results of micro-Laue diffraction study [d in Å(hkil)(I)] are 2.7950 ($20\bar{2}5$) (100); 5.7143 (0006) (60); 1.7671 ($22\bar{4}0$) (44.4); 3.0486 ($20\bar{2}1$) (39.4); 5.7650 ($10\bar{1}2$) (38.6); 2.5956 ($20\bar{2}7$) (37.8); 3.0058 ($11\bar{2}6$) (36.5); and 1.5029 ($4\bar{2}\bar{2}12$) (35.3). Ferrotorryweiserite and the associated PGM crystallized from microvolumes of residual melt at late stages of crystallization of grains of Os- and Ir-dominant alloys occurred in lode zones of chromitites of the Lysanskiy layered complex. In a particular case, the residual melt is disposed peripherally around a core containing a disequilibrium association of magnesian olivine (Fo 72.9–75.6 ) and albite (Ab 81.6–86.4 ), with the development of skeletal crystals of titaniferous augite: Wo 40.8–43.2 En 26.5–29.3 Fs 20.3–22.6 Aeg 6.9–9.5 (2.82–3.12 wt.% TiO 2 ). Ferrotorryweiserite represents the Fe-dominant analog of torryweiserite. We also report occurrences of ferrotorryweiserite in the Marathon deposit, Coldwell Complex, Ontario, Canada, and infer the existence of the torryweiserite–ferrotorryweiserite solid solution in other deposits and complexes.

58 GEOSCIENCES↗
NASA NTRS2013

Dynamics and Control of a Disordered System in Space

In this paper, we present some ideas regarding the modeling, dynamics and control aspects of granular spacecraft. Granular spacecraft are complex multibody systems composed of a spatially disordered distribution of a large number of elements, for instance a cloud of N grains in orbit, with N greater than 10(exp 3). These grains can be large (Cubesat-size) or small (mm-size), and can be active, i.e., a fully equipped vehicle capable sensing their own position and attitude, and enabled with propulsion means, or entirely passive. The ultimate objective would be to study the behavior of the single grains and of large ensembles of grains in orbit and to identify ways to guide and control the shape of a cloud composed of these grains so that it can perform a useful function in space, for instance, as an element of an optical imaging system for astrophysical applications. This concept, in which the aperture does not need to be continuous and monolithic, would increase the aperture size several times compared to large NASA observatories such as ATLAST, allowing for a true Terrestrial Planet Imager that would be able to resolve exo-planet details and do meaningful spectroscopy on distant world. In the paper, we address the modeling and autonomous operation of a distributed assembly (the cloud) of large numbers of highly miniaturized space-borne elements (the grains). A multi-scale, multi-physics model is proposed of the dynamics of the cloud in orbit, as well as a control law for cloud shape maintenance, and preliminary simulation studies yield an estimate of the computational effort, indicating a scale factor of approximately N(exp 1.4) as a function of the number of grains. A granular spacecraft can be defined as a collection of a large number of space-borne elements (in the 1000s) designed and controlled such that a desirable collective behavior emerges, either from the interactions among neighboring grains, and/or between the grains and the environment. In this paper, each grain is considered to be a highly miniaturized spacecraft which has limited size and mass, hence it has limited actuation, limited propulsive capability, limited power, limited sensing, limited communication, limited computational resources, limited range of motion, limited lifetime, and may be expendable. The modeling and dynamics of clouds of vehicles is more challenging than with conventional vehicles because we are faced with a probabilistic vehicle composed of a large number of physically disconnected vehicles. First, different scales of motion occur simultaneously in a cloud: translations and rotations of the cloud as a whole (macro-dynamics), relative rotation and translation of one cloud member with respect to another (meso-dynamics), and individual cloud member dynamics (micro-dynamics). Second, the control design needs to be tolerant of the system complexity, of the system architecture (centralized vs. decentralized large scale system control) as well as robust to un-modeled dynamics and noise sources. Figure 1, top left, shows the kinematic parameters of a 1000 element cloud in orbit. The motion of the system is described with respect to a local vertical-local horizontal (LV-LH) orbiting reference frame (x,y,z)=F(sub ORF) of origin O(sub ORF) which rotates with mean motion omega and orbital semi-major axis R(sub 0). The orbital geometry at the initial time is defined in terms of its six orbital elements, and the orbital dynamics equation for point O(sub ORF) is propagated forward in time under the influence of the gravitational field of the primary and other external perturbations, described below. The origin of this frame coincides with the initial position of the center of mass of the system, and the coordinate axes are z along the local vertical, x toward the flight direction, and y in the orbit normal direction. The assumptions we used to model the dynamics are as follows: 1) The inertial frame is fixed at Earth's center. 2) The orbiting Frame ORF follows Keplerian orbit. 3) the cloud system dynamics is referred to ORF. 4) the attitude of each grain uses the principal body frame as body fixed frame. 5) the atmosphere is assumed to be rigidly rotating with the Earth. Regarding the grains forming the cloud: 1) each grain is modeled as a rigid body; 2) a simple attitude estimator provides attitude estimates, 3) a simple guidance logic commands the position and attitude of each grain, 4) a simple local feedback controller based on PD control of local states is used to stabilize the attitude of the vehicle. Regarding the cloud: 1) the cloud as a whole is modeled as an equivalent rigid body in orbit, and 2) an associated graph establishes agent connectivity and enables coupling between modes of motion at the micro and macro scales; 3) a simple guidance and estimation logic is modeled to estimate and command the attitude of this equivalent rigid body; 4) a cloud shape maintenance controller is based on the dynamics of a stable virtual truss in the orbiting frame. Regarding the environmental perturbations acting on the cloud: 1) a non-spherical gravity field including JO (Earth's spherical field) zonal component, J2 (Earth's oblateness) and J3 zonal components is implemented; 2) atmospheric drag is modeled with an exponential model; 3) solar pressure is modeled assuming the Sun is inertially fixed; and 4) the Earth's magnetic field is model using an equivalent dipole model. The equations of motion are written in a referential system with respect to the origin of the orbiting frame and the state is propagated forward in time using an incremental predictor-corrector scheme. A representative cloud with varying number of grains is simulated to identify the limitations in computation time as the number of grains grows. We derive a control law to track a desired surface in the ORF (equivalently to maintain a reference cloud shape) by defining an error from a desired surface shape, and designing a control law that is exponentially stable and reduces the tracking error to zero. Figure 1 (top right) shows a comparison of various requirements for simulation of single spacecraft vs. granular spacecraft, indicating the high degree of complexity that needs to be taken into consideration. The ORF components of control force required by one of the grains is, for this particular case, in the micro-Newton range. However, no attempt has been made yet to reconfigure (or re-orient) the cloud configuration internally, for which forces in the milli-Newton level are expected, depending on the time required to do the reconfiguration. Figure 1, bottom, shows the computation time as a function of the number of grains, indicating an order N(exp 1.43) scaling on a 8 Gb, 1067 MHz RAM MacOSX computer with a 3.06 GHz Intel Core 2 Duo processor. With this metric, the same simulation for a system of N=1000 grains would take 5.4 hours, and 146 hours (i.e., 6 days) for a system with N=10,000 grains. Therefore, efficient ways to simulate this complex system, where not only the time scales of natural system dynamics, but also the sampling times of the Guidance, Navigation, and Control are included, remain to be explored. Additional details on the cloud modeling, dynamics, and control will be described in the paper.

simulation↗