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DOE OSTI2020

Materials Data on KSnAs by Materials Project

KSnAs is trigonal omega-derived structured and crystallizes in the hexagonal P6_3mc space group. The structure is two-dimensional and consists of two KSnAs sheets oriented in the (0, 0, 1) direction. K1+ is bonded in a 3-coordinate geometry to three equivalent As3- atoms. All K–As bond lengths are 3.33 Å. Sn2+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent As3- atoms. All Sn–As bond lengths are 2.76 Å. As3- is bonded to three equivalent K1+ and three equivalent Sn2+ atoms to form edge-sharing AsK3Sn3 octahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K4CdP2 by Materials Project

K4CdP2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a trigonal non-coplanar geometry to three equivalent P3- atoms. All K–P bond lengths are 3.40 Å. In the second K1+ site, K1+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing KP4 tetrahedra. There are one shorter (3.26 Å) and three longer (3.46 Å) K–P bond lengths. Cd2+ is bonded in a linear geometry to two equivalent P3- atoms. Both Cd–P bond lengths are 2.42 Å. P3- is bonded in a body-centered cubic geometry to seven K1+ and one Cd2+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K4ZnAs2 by Materials Project

K4ZnAs2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a trigonal non-coplanar geometry to three equivalent As3- atoms. All K–As bond lengths are 3.47 Å. In the second K1+ site, K1+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing KAs4 tetrahedra. There are one shorter (3.34 Å) and three longer (3.50 Å) K–As bond lengths. Zn2+ is bonded in a linear geometry to two equivalent As3- atoms. Both Zn–As bond lengths are 2.33 Å. As3- is bonded in a distorted body-centered cubic geometry to seven K1+ and one Zn2+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K4BeP2 by Materials Project

K4BeP2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a trigonal non-coplanar geometry to three equivalent P3- atoms. All K–P bond lengths are 3.35 Å. In the second K1+ site, K1+ is bonded to four equivalent P3- atoms to form a mixture of edge and corner-sharing KP4 tetrahedra. There are one shorter (3.28 Å) and three longer (3.43 Å) K–P bond lengths. Be2+ is bonded in a linear geometry to two equivalent P3- atoms. Both Be–P bond lengths are 2.00 Å. P3- is bonded in a distorted single-bond geometry to seven K1+ and one Be2+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K2RbCO3F by Materials Project

RbK2CO3F crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Rb1+ is bonded to five O2- and two equivalent F1- atoms to form distorted RbO5F2 pentagonal bipyramids that share corners with two equivalent RbO5F2 pentagonal bipyramids, corners with four KO5F2 pentagonal bipyramids, edges with two equivalent RbO5F2 pentagonal bipyramids, edges with four KO5F2 pentagonal bipyramids, and faces with four KO5F2 pentagonal bipyramids. There are a spread of Rb–O bond distances ranging from 2.92–3.04 Å. There are one shorter (2.72 Å) and one longer (2.73 Å) Rb–F bond lengths. There are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to five O2- and two equivalent F1- atoms to form distorted KO5F2 pentagonal bipyramids that share corners with two equivalent KO5F2 pentagonal bipyramids, corners with four equivalent RbO5F2 pentagonal bipyramids, edges with two equivalent KO5F2 pentagonal bipyramids, edges with four equivalent RbO5F2 pentagonal bipyramids, and faces with four equivalent KO5F2 pentagonal bipyramids. There are a spread of K–O bond distances ranging from 2.88–3.03 Å. Both K–F bond lengths are 2.66 Å. In the second K1+ site, K1+ is bonded to five O2- and two equivalent F1- atoms to form distorted KO5F2 pentagonal bipyramids that share corners with two equivalent RbO5F2 pentagonal bipyramids, corners with four KO5F2 pentagonal bipyramids, edges with two equivalent RbO5F2 pentagonal bipyramids, edges with four KO5F2 pentagonal bipyramids, faces with two equivalent RbO5F2 pentagonal bipyramids, and faces with two equivalent KO5F2 pentagonal bipyramids. There are a spread of K–O bond distances ranging from 2.90–3.03 Å. There are one shorter (2.62 Å) and one longer (2.63 Å) K–F bond lengths. In the third K1+ site, K1+ is bonded to five O2- and two equivalent F1- atoms to form distorted KO5F2 pentagonal bipyramids that share corners with six KO5F2 pentagonal bipyramids, edges with six KO5F2 pentagonal bipyramids, and faces with four equivalent RbO5F2 pentagonal bipyramids. There are a spread of K–O bond distances ranging from 2.89–3.03 Å. Both K–F bond lengths are 2.67 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. All C–O bond lengths are 1.31 Å. In the second C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. All C–O bond lengths are 1.31 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Rb1+, three K1+, and one C4+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Rb1+, three K1+, and one C4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Rb1+, four K1+, and one C4+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Rb1+, three K1+, and one C4+ atom. F1- is bonded to two equivalent Rb1+ and four K1+ atoms to form corner-sharing FK4Rb2 octahedra. The corner-sharing octahedra tilt angles range from 21–22°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K3Cu11Te16 by Materials Project

K3Cu11Te16 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 1-coordinate geometry to eight Te+0.88- atoms. There are a spread of K–Te bond distances ranging from 3.45–3.95 Å. In the second K1+ site, K1+ is bonded to twelve Te+0.88- atoms to form KTe12 cuboctahedra that share corners with fourteen CuTe4 tetrahedra, edges with two equivalent KTe12 cuboctahedra, and faces with eight CuTe4 tetrahedra. There are a spread of K–Te bond distances ranging from 3.68–3.85 Å. There are four inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to four Te+0.88- atoms to form CuTe4 tetrahedra that share a cornercorner with one KTe12 cuboctahedra, corners with four CuTe4 tetrahedra, edges with two CuTe4 tetrahedra, and a faceface with one KTe12 cuboctahedra. There are a spread of Cu–Te bond distances ranging from 2.60–2.73 Å. In the second Cu1+ site, Cu1+ is bonded to four Te+0.88- atoms to form CuTe4 tetrahedra that share a cornercorner with one KTe12 cuboctahedra, corners with seven CuTe4 tetrahedra, an edgeedge with one CuTe4 tetrahedra, and a faceface with one KTe12 cuboctahedra. There are a spread of Cu–Te bond distances ranging from 2.58–2.65 Å. In the third Cu1+ site, Cu1+ is bonded to four Te+0.88- atoms to form CuTe4 tetrahedra that share corners with two equivalent KTe12 cuboctahedra and corners with four equivalent CuTe4 tetrahedra. All Cu–Te bond lengths are 2.61 Å. In the fourth Cu1+ site, Cu1+ is bonded to four Te+0.88- atoms to form distorted CuTe4 tetrahedra that share corners with two equivalent KTe12 cuboctahedra, corners with four equivalent CuTe4 tetrahedra, and edges with two equivalent CuTe4 tetrahedra. There are two shorter (2.59 Å) and two longer (2.60 Å) Cu–Te bond lengths. There are six inequivalent Te+0.88- sites. In the first Te+0.88- site, Te+0.88- is bonded in a 6-coordinate geometry to two equivalent K1+, three Cu1+, and one Te+0.88- atom. The Te–Te bond length is 2.89 Å. In the second Te+0.88- site, Te+0.88- is bonded in a distorted trigonal non-coplanar geometry to three K1+ and three Cu1+ atoms. In the third Te+0.88- site, Te+0.88- is bonded in a 7-coordinate geometry to two equivalent K1+, four Cu1+, and one Te+0.88- atom. The Te–Te bond length is 2.93 Å. In the fourth Te+0.88- site, Te+0.88- is bonded in a 3-coordinate geometry to one K1+ and three Cu1+ atoms. In the fifth Te+0.88- site, Te+0.88- is bonded in a 2-coordinate geometry to one K1+ and two equivalent Cu1+ atoms. In the sixth Te+0.88- site, Te+0.88- is bonded in a 2-coordinate geometry to two equivalent K1+, one Cu1+, and two equivalent Te+0.88- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K7(FeS2)5 by Materials Project

K7(FeS2)5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of K–S bond distances ranging from 3.34–3.50 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of K–S bond distances ranging from 3.11–3.82 Å. In the third K1+ site, K1+ is bonded to six S2- atoms to form distorted KS6 octahedra that share corners with eight FeS4 tetrahedra, edges with two FeS4 tetrahedra, and faces with two equivalent KS6 octahedra. There are a spread of K–S bond distances ranging from 3.13–3.48 Å. In the fourth K1+ site, K1+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of K–S bond distances ranging from 3.19–3.81 Å. There are three inequivalent Fe+2.60+ sites. In the first Fe+2.60+ site, Fe+2.60+ is bonded to four S2- atoms to form FeS4 tetrahedra that share corners with four equivalent KS6 octahedra, an edgeedge with one KS6 octahedra, and edges with two FeS4 tetrahedra. The corner-sharing octahedra tilt angles range from 17–67°. There are three shorter (2.26 Å) and one longer (2.29 Å) Fe–S bond lengths. In the second Fe+2.60+ site, Fe+2.60+ is bonded to four S2- atoms to form FeS4 tetrahedra that share corners with four equivalent KS6 octahedra and edges with two equivalent FeS4 tetrahedra. The corner-sharing octahedra tilt angles range from 23–47°. There are two shorter (2.24 Å) and two longer (2.26 Å) Fe–S bond lengths. In the third Fe+2.60+ site, Fe+2.60+ is bonded to four S2- atoms to form FeS4 tetrahedra that share corners with two equivalent KS6 octahedra, an edgeedge with one KS6 octahedra, and edges with two FeS4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–68°. There are a spread of Fe–S bond distances ranging from 2.23–2.31 Å. There are five inequivalent S2- sites. In the first S2- site, S2- is bonded in a 7-coordinate geometry to five K1+ and two equivalent Fe+2.60+ atoms. In the second S2- site, S2- is bonded in a 7-coordinate geometry to five K1+ and two Fe+2.60+ atoms. In the third S2- site, S2- is bonded in a 6-coordinate geometry to four K1+ and two Fe+2.60+ atoms. In the fourth S2- site, S2- is bonded in a 6-coordinate geometry to five K1+ and two Fe+2.60+ atoms. In the fifth S2- site, S2- is bonded in a 6-coordinate geometry to four K1+ and two Fe+2.60+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Comparative Study of Solvatomorphs of Stryker's Reagent Using MicroED and Quantum Mechanics

Abstract The atomic position of hydrogen atoms in metal hydrides has been a long‐standing structural question in inorganic chemistry given that hydride delivery is integral to diverse chemical reactions. Microcrystal electron diffraction (microED), with it's increased sensitivity toward hydrogen atoms relative to X‐ray diffraction, offers a potential path to addressing this challenge. Herein, the first microED study of Stryker's reagent is reported, resulting in the structure of a new benzene solvate. Improved accuracy for hydrogen atom positions was obtained via a quantum crystallography (QCr) approach, Hirshfeld atom refinement (HAR). Structural and topological analysis supports edge bridging hydrides in the microED structure of a THF solvate form, consistent with previous diffraction studies. Interestingly, analysis of a new benzene solvate, discovered in this study, is consistent with mixed edge‐ and face‐bridging hydrides.

Jha, Kunal K. [Division of Chemistry &amp, Chemica↗

NASA NTRS1974

Rigorous precision p-wave positron-hydrogen scattering calculation

Rigorous lower-bound p-wave positron-hydrogen phase shifts are calculated below the positronium pickup threshold. The wave function is expanded in terms of the two linearly independent D functions each multiplied by an associated Hilleraas-type radial function with two parameters. Adiabatic and nonadiabatic corrections have been included. The results are found to be larger than Armstead's (1968) in all cases near the upper edge of his estimated uncertainty.

Bhatia, A. K.↗

NASA NTRS1975

Laser velocimeter measurements of rotor blade loads and tip vortex rollup

A method for obtaining and analyzing the instantaneous velocities of helicopter rotor flow fields through use of a laser velocimeter capable of simultaneously sensing two components of velocity is described. Rotor blade aerodynamic loads may be computed from the velocity distributions near the blades. The experiment was conducted with a 2.13 m (7 ft) diameter model helicopter rotor operating in a wind tunnel. Velocity distributions are presented which document the flow field near the advancing blade. Circulation is calculated from the velocity measurements, and the radial distribution of circulation is discussed. The influence of the tip vortex from the preceding blade is apparent in this distribution. Tip vortex rollup on the advancing blade was documented by making a series of measurements at various distances behind the blade. Effects of blade drag are evident in the velocities behind the blade trailing edge.

Biggers, J. C.↗

NASA NTRS1979

Scaling laws and edge effects for polymer surface discharges

Specimens of Mylar sheet were exposed to a 20 kV electron beam. The resulting surface discharge arcs were photographed and the discharge current into a metal backing plate measured as a function of time. The area of the Mylar sheet was defined by a round aperture in a close-fitting metal mask, and the current pulse characteristics were plotted against area on log-log paper. The plots appear as straight lines (due to power-law behavior) with slopes of 0.50 for the peak current, 1.00 for the charge released, 1.49 for the energy and 0.55 for the pulse duration. Evidence is presented for the occurrence of banded charge distributions near grounded edges, on both Teflon and Mylar.

Balmain, K. G.↗

NASA NTRS1983

Annulus wall boundary layer development in a compressor stage, including the effects of tip clearance

The end-wall boundary layer development in a compressor stage, including the inlet guide vane (IGV) passage and the rotor passage, was measured. The measurement upstream of the rotor and inside the IGV passage were carried out with a five-hole probe. The data (blade-to-blade) inside the IGV passage were carried out with a five-hole probe. The data (blade-to-blade) inside the rotor passage were measured using a three-sensor rotating hot-wire below the tip clearance region and "V' configuration probe inside the clearance region. The rotor exit measurements (blade-to-blade) were acquired with a laser Doppler velocimeter. The velocity profiles and the integral properties are presented and interpreted. The boundary layer is comparatively well behaved up to the leading edge of the rotor, beyond which complex interactions result in very unconventional profiles. The momentum thicknesses decrease in the leakage flow region of the rotor. The momentum thicknesses and the limiting streamline angles predicted from a momentum integral technique agree well with the data up to the leading edge of the rotor.

Lakshminarayana, B.↗

NASA NTRS1986

Far-infrared and radio observations of DR 6, DR 7, and DR 22

Far-infrared maps are presented for three young H II regions in the Cygnus X region. DR 6 and 7 were mapped in the wavelength band from 40 to 250 microns at 1 arcmin resolution, while DR 22 was mapped in the same band and also at 100-250 microns, providing dust temperature and optical depth information. New VLA maps of these sources are also presented. It is concluded that DR 6 and 7 are powered by clusters of late O or early B type stars, with ages 100,000 yr or less, while DR 22 appears to be produced by a single O6 ZAMS star. Existing (C-12)O maps suggest that the formation of these objects occurred near the edges of molecular clouds.

Odenwald, S.↗

NASA NTRS1989

Arc restrike in the rail accelerator

One of the causes of the degradation in rail accelerator performance is the formation of a secondary arc. Experimental evidence of arc restrike and the subsequent growth of this secondary arc is presented. A simple analytical treatment of arc restrike is developed in terms of breakdown of residual vapor atoms. It is found that after the passage of the primary arc, the bore volume contains a large number of residual neutral vapor atoms. If the density of these atoms is in excess of the critical density, then for a certain length of time the condition exists in the bore for the formation of a secondary arc. Evaporation of atoms from the bore surfaces cannot provide a sufficient number of atoms for an arc restrike. A likely source of the high residual atom density is the leakage of a portion of the ablated material that is added to the trailing edge of the primary arc.

Ray, Pradosh K.↗

NASA NTRS1992

Adaptive explicit and implicit finite element methods for transient thermal analysis

The application of adaptive finite element methods to the solution of transient heat conduction problems in two dimensions is investigated. The computational domain is represented by an unstructured assembly of linear triangular elements and the mesh adaptation is achieved by local regeneration of the grid, using an error estimation procedure coupled to an automatic triangular mesh generator. Two alternative solution procedures are considered. In the first procedure, the solution is advanced by explicit timestepping, with domain decomposition being used to improve the computational efficiency of the method. In the second procedure, an algorithm for constructing continuous lines which pass only once through each node of the mesh is employed. The lines are used as the basis of a fully implicit method, in which the equation system is solved by line relaxation using a block tridiagonal equation solver. The numerical performance of the two procedures is compared for the analysis of a problem involving a moving heat source applied to a convectively cooled cylindrical leading edge.

Probert, E. J.↗

NASA NTRS1994

Year-round measurements of ozone at 66 deg S with a visible spectrometer

In March 1990, a zenith-sky UV-visible spectrometer of the design 'Systeme Automatique d'Obervation Zenithal' (SAOZ) was installed at Faraday in Antarctica (66.3 deg S, 64.3 deg W). SAOZ records spectra between 290 and 600 nm during daylight. Its analysis program fits laboratory spectra of constituents, at various wavelengths, to the differential of the ratio of the observed spectrum and a reference spectrum. The least-squares fitting procedure minimizes the sum-of-squares of residuals. Ozone is deduced from absorption in its visible bands between 500 and 560 nm. The fortunate colocation of this SAOZ with the well-calibrated Dobson at Faraday has allowed us to examine the calibration of the zero of the SAOZ, difficult at visible wavelengths because of the small depth of absorption. Here we describe recent improvements and limitations to this calibration, and discuss SAOZ measurements of ozone during winter in this important location at the edge of the Antarctic vortex.

Roscoe, Howard K.↗

NASA NTRS1994

System and process for detecting and monitoring surface defects

A system and process for detecting and monitoring defects in large surfaces such as the field joints of the container segments of a space shuttle booster motor. Beams of semi-collimated light from three non-parallel fiber optic light panels are directed at a region of the surface at non-normal angles of expected incidence. A video camera gathers some portion of the light that is reflected at an angle other than the angle of expected reflectance, and generates signals which are analyzed to discern defects in the surface. The analysis may be performed by visual inspection of an image on a video monitor, or by inspection of filtered or otherwise processed images. In one alternative embodiment, successive predetermined regions of the surface are aligned with the light source before illumination, thereby permitting efficient detection of defects in a large surface. Such alignment is performed by using a line scan gauge to sense the light which passes through an aperture in the surface. In another embodiment a digital map of the surface is created, thereby permitting the maintenance of records detailing changes in the location or size of defects as the container segment is refurbished and re-used. The defect detection apparatus may also be advantageously mounted on a fixture which engages the edge of a container segment.

Mueller, Mark K.↗

DOE OSTI2020

Materials Data on K3SmN6 by Materials Project

K3SmN6 is Ilmenite-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 6-coordinate geometry to six N1- atoms. There are four shorter (2.76 Å) and two longer (3.35 Å) K–N bond lengths. In the second K1+ site, K1+ is bonded to six N1- atoms to form distorted KN6 octahedra that share corners with two equivalent SmN6 octahedra, edges with two equivalent SmN6 octahedra, and edges with three equivalent KN6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are a spread of K–N bond distances ranging from 2.79–3.08 Å. Sm3+ is bonded to six N1- atoms to form SmN6 octahedra that share corners with four equivalent KN6 octahedra and edges with four equivalent KN6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are four shorter (2.35 Å) and two longer (2.38 Å) Sm–N bond lengths. There are two inequivalent N1- sites. In the first N1- site, N1- is bonded in a distorted see-saw-like geometry to three K1+ and one Sm3+ atom. In the second N1- site, N1- is bonded in a distorted see-saw-like geometry to three K1+ and one Sm3+ atom.

36 MATERIALS SCIENCE↗