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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KIO2 by Materials Project

KO2I crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. K is bonded to six equivalent O atoms to form edge-sharing KO6 octahedra. There are four shorter (2.67 Å) and two longer (2.93 Å) K–O bond lengths. O is bonded to three equivalent K and two equivalent I atoms to form a mixture of distorted edge and corner-sharing OK3I2 square pyramids. Both O–I bond lengths are 2.23 Å. I is bonded in a distorted square co-planar geometry to four equivalent O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K7Ta(SO4)6 by Materials Project

K7Ta(SO4)6 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six equivalent O2- atoms to form KO6 octahedra that share corners with six equivalent SO4 tetrahedra and edges with six equivalent KO6 octahedra. All K–O bond lengths are 2.74 Å. In the second K1+ site, K1+ is bonded to six O2- atoms to form KO6 octahedra that share corners with two equivalent KO6 octahedra, corners with six equivalent SO4 tetrahedra, and edges with three KO6 octahedra. The corner-sharing octahedral tilt angles are 77°. There are a spread of K–O bond distances ranging from 2.72–2.98 Å. Ta5+ is bonded to six equivalent O2- atoms to form TaO6 octahedra that share corners with six equivalent SO4 tetrahedra. All Ta–O bond lengths are 1.98 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share a cornercorner with one TaO6 octahedra and corners with seven KO6 octahedra. The corner-sharing octahedra tilt angles range from 28–64°. There are a spread of S–O bond distances ranging from 1.47–1.57 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one S6+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+ and one S6+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Ta5+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K7Nb(SO4)6 by Materials Project

K7Nb(SO4)6 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six equivalent O2- atoms to form KO6 octahedra that share corners with six equivalent SO4 tetrahedra and edges with six equivalent KO6 octahedra. All K–O bond lengths are 2.74 Å. In the second K1+ site, K1+ is bonded to six O2- atoms to form KO6 octahedra that share corners with two equivalent KO6 octahedra, corners with six equivalent SO4 tetrahedra, and edges with three KO6 octahedra. The corner-sharing octahedral tilt angles are 77°. There are a spread of K–O bond distances ranging from 2.72–2.98 Å. Nb5+ is bonded to six equivalent O2- atoms to form NbO6 octahedra that share corners with six equivalent SO4 tetrahedra. All Nb–O bond lengths are 2.00 Å. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with seven KO6 octahedra. The corner-sharing octahedra tilt angles range from 29–65°. There are a spread of S–O bond distances ranging from 1.47–1.57 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one S6+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one S6+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Nb5+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one S6+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1998

Prediction of Unsteady Transitional Layers in Turbomachinery Using Navier Stokes Equations

The objective of the research reported in this presentation is to develop computational techniques for the prediction of unsteady transitional flows associated with the rotor stator interaction in turbomachinery. Three low-Reynolds number turbulence models are incorporated in two unsteady Navier-Stokes codes (one is pressure based and the other is time marching with Runge-Kutta time stepping) and evaluated for accuracy in predicting the onset and the end of unsteady transitional patches due to wake passing. The best model is then used for modification and improvement for the leading edge effect. An existing steady Navier-Stokes code was modified to include pseudo-time stepping, which provided acceleration from 5 to 25 times that of the original code. A systematic validation procedure was implemented to assess the effects of the grid, artificial dissipation, physical, and the pseudo-time step for an accurate prediction of transitional flows resulting from the rotor-stator interaction. The ability of the Navier-Stokes code to predict the unsteady transitional flow on a turbomachinery blade is demonstrated. The unsteady pressure and velocity fields are in good agreement with the experimental data and the prediction from the Euler/boundary layer approach. The numerical solver was able to capture all zones (wake induced transitional strip, wake induced turbulent strip, calmed region, etc.) associated with wake induced transition in a compressor cascade. Another significant step is the assessment of k-epsilon turbulence models, including the leading edge modifications. Best results were obtained from the FLB model. The LB model predicted earlier inception of the transition and shorter transition length. Modification of the k-epsilon model was found to be essential for an accurate prediction of the unsteady transitional flow in a compressor cascade. The CH model failed to predict the unsteady transitional flow. Predicted boundary layer was turbulent from the leading edge, even with the modification of the k-epsilon model near the stagnation point. A comparison of the instantaneous shape factor, the skin friction coefficient, and the momentum thickness indicates that the Navier-Stokes predictions are reasonably good. Interaction between the upstream wake and stator wake results in shedding of unsteady vortices from the trailing edge and increased dissipation in the stator wake and, as a consequence, increased rate of decay of the stator wake. The procedure developed at Penn State should aid the designers of turbomachinery in allowing for the unsteady transitional flows due to rotor-stator interaction.

Lakshminarayana, B.↗
NASA NTRS2004

Photoionization Modeling and the K Lines of Iron

We calculate the efficiency of iron K line emission and iron K absorption in photoionized models using a new set of atomic data. These data are more comprehensive than those previously applied to the modeling of iron K lines from photoionized gases, and allow us to systematically examine the behavior of the properties of line emission and absorption as a function of the ionization parameter, density and column density of model constant density clouds. We show that, for example, the net fluorescence yield for the highly charged ions is sensitive to the level population distribution produced by photoionization, and these yields are generally smaller than those predicted assuming the population is according to statistical weight. We demonstrate that the effects of the many strongly damped resonances below the K ionization thresholds conspire to smear the edge, thereby potentially affecting the astrophysical interpretation of absorption features in the 7-9 keV energy band. We show that the centroid of the ensemble of K(alpha) lines, the K(beta) energy, and the ratio of the K(alpha(sub 1)) to K(alpha(sub 2)) components are all diagnostics of the ionization parameter of our model slabs.

Kallman, T. R.↗
DOE OSTI2020

Materials Data on K by Materials Project

K is Magnesium structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. K is bonded to twelve equivalent K atoms to form a mixture of face, edge, and corner-sharing KK12 cuboctahedra. There are six shorter (4.68 Å) and six longer (4.76 Å) K–K bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2PbO2 by Materials Project

K2PbO2 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 3-coordinate geometry to three O2- atoms. There are a spread of K–O bond distances ranging from 2.68–2.70 Å. In the second K1+ site, K1+ is bonded in a see-saw-like geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.69–2.92 Å. In the third K1+ site, K1+ is bonded to five O2- atoms to form edge-sharing KO5 trigonal bipyramids. There are a spread of K–O bond distances ranging from 2.73–2.86 Å. In the fourth K1+ site, K1+ is bonded to five O2- atoms to form edge-sharing KO5 trigonal bipyramids. There are a spread of K–O bond distances ranging from 2.70–2.90 Å. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a distorted T-shaped geometry to three O2- atoms. There are a spread of Pb–O bond distances ranging from 2.14–2.31 Å. In the second Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Pb–O bond distances ranging from 2.15–2.27 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four K1+ and two equivalent Pb2+ atoms to form OK4Pb2 octahedra that share corners with three equivalent OK3Pb2 trigonal bipyramids and edges with eight OK4Pb2 octahedra. In the second O2- site, O2- is bonded to five K1+ and one Pb2+ atom to form OK5Pb octahedra that share corners with three equivalent OK5Pb octahedra, edges with four OK4Pb2 octahedra, and edges with three equivalent OK3Pb2 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 10–16°. In the third O2- site, O2- is bonded to five K1+ and one Pb2+ atom to form OK5Pb octahedra that share corners with three equivalent OK5Pb octahedra, a cornercorner with one OK3Pb2 trigonal bipyramid, edges with seven OK4Pb2 octahedra, and an edgeedge with one OK3Pb2 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 10–16°. In the fourth O2- site, O2- is bonded to three K1+ and two equivalent Pb2+ atoms to form distorted OK3Pb2 trigonal bipyramids that share corners with four OK4Pb2 octahedra, edges with four OK5Pb octahedra, and an edgeedge with one OK3Pb2 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 28–78°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCd(PO3)3 by Materials Project

KCd(PO3)3 crystallizes in the hexagonal P-6c2 space group. The structure is three-dimensional. K1+ is bonded to six equivalent O2- atoms to form distorted KO6 octahedra that share corners with six equivalent PO4 tetrahedra and edges with three equivalent CdO6 octahedra. All K–O bond lengths are 2.85 Å. Cd2+ is bonded to six equivalent O2- atoms to form CdO6 octahedra that share corners with six equivalent PO4 tetrahedra and edges with three equivalent KO6 octahedra. All Cd–O bond lengths are 2.30 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent KO6 octahedra, corners with two equivalent CdO6 octahedra, and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 43–59°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Cd2+, and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCa(PO3)3 by Materials Project

KCa(PO3)3 crystallizes in the hexagonal P-6c2 space group. The structure is three-dimensional. K1+ is bonded to six equivalent O2- atoms to form distorted KO6 octahedra that share corners with six equivalent PO4 tetrahedra and edges with three equivalent CaO6 octahedra. All K–O bond lengths are 2.85 Å. Ca2+ is bonded to six equivalent O2- atoms to form CaO6 octahedra that share corners with six equivalent PO4 tetrahedra and edges with three equivalent KO6 octahedra. All Ca–O bond lengths are 2.36 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent KO6 octahedra, corners with two equivalent CaO6 octahedra, and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–58°. There is two shorter (1.50 Å) and two longer (1.62 Å) P–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Ca2+, and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KMn(PO3)3 by Materials Project

KMn(PO3)3 crystallizes in the hexagonal P-6c2 space group. The structure is three-dimensional. K1+ is bonded to six equivalent O2- atoms to form distorted KO6 octahedra that share corners with six equivalent PO4 tetrahedra and edges with three equivalent MnO6 octahedra. All K–O bond lengths are 2.81 Å. Mn2+ is bonded to six equivalent O2- atoms to form MnO6 octahedra that share corners with six equivalent PO4 tetrahedra and edges with three equivalent KO6 octahedra. All Mn–O bond lengths are 2.20 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent KO6 octahedra, corners with two equivalent MnO6 octahedra, and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–60°. There is two shorter (1.50 Å) and two longer (1.62 Å) P–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Mn2+, and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KC by Materials Project

KC1 is Halite, Rock Salt structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. K is bonded to six equivalent C atoms to form a mixture of edge and corner-sharing KC6 octahedra. The corner-sharing octahedral tilt angles are 0°. All K–C bond lengths are 3.09 Å. C is bonded to six equivalent K atoms to form a mixture of edge and corner-sharing CK6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KB by Materials Project

BK1 is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K is bonded to six equivalent B atoms to form a mixture of edge and corner-sharing KB6 octahedra. The corner-sharing octahedral tilt angles are 0°. All K–B bond lengths are 3.15 Å. B is bonded to six equivalent K atoms to form a mixture of edge and corner-sharing BK6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Metal (hydr)oxide surface precipitates and their effects on potassium sorption

Surface precipitation has been shown to occur on rapid time scales in clay and metal oxide mineral systems. The formation of surface precipitates is hypothesized to present new potential sorption sites for potassium (K), where K can become incorporated into newly formed interlayer spaces (e.g., between tetrahedral–octahedral–tetrahedral stacked sheets). The objective of this study is to determine the effects of newly formed mineral surface precipitates on K sorption. Potassium adsorption experiments were conducted by utilizing Al 2 O 3 and SiO 2 sorbents in the presence of various cations (magnesium, zinc, and nickel) that helped to catalyze the formation of surface precipitates. Dissolved concentrations of elements were monitored via inductively coupled plasma optical emission spectrometry (ICP-OES). Solids were characterized via X-ray diffraction (XRD), and K surface complexation was analyzed via X-ray absorption near edge structure (XANES) spectroscopy. X-ray diffraction analysis indicated bayerite, layered double hydroxides (LDH), and silicated LDH were formed as reaction products, thus creating new surface sites for potential K adsorption. The presence of Si increased K adsorption perhaps due to its role in the formation of LDH surface precipitates. When the differences between observed and theoretical surface area normalized K sorption densities were averaged, a 31% increase in K adsorption was observed in the presence of Si. XANES analysis indicated that the binding mechanism of K to Si is different than that of K to Al, perhaps due to the presence of inner-sphere complexation of K to Al-oxide. Samples reacted for one month versus one week yielded more intense XANES post-edge peaks which indicated that the K sorption complex changes over time. Altogether, our findings provide novel insights into the mechanisms of K fixation in soil and has high implication in providing improved K fertilizer recommendation to growers.

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

Materials Data on K3CuO2 by Materials Project

K3CuO2 crystallizes in the tetragonal P4_12_12 space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to four O2- atoms to form a mixture of distorted corner and edge-sharing KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.79–2.88 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.63–3.12 Å. In the third K1+ site, K1+ is bonded to four O2- atoms to form a mixture of distorted corner and edge-sharing KO4 tetrahedra. There are two shorter (2.79 Å) and two longer (2.94 Å) K–O bond lengths. In the fourth K1+ site, K1+ is bonded to four O2- atoms to form a mixture of corner and edge-sharing KO4 tetrahedra. There are two shorter (2.76 Å) and two longer (2.91 Å) K–O bond lengths. Cu1+ is bonded in a linear geometry to two O2- atoms. Both Cu–O bond lengths are 1.82 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 7-coordinate geometry to six K1+ and one Cu1+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to six K1+ and one Cu1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KGe by Materials Project

KGe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K is bonded to six equivalent Ge atoms to form a mixture of edge and corner-sharing KGe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All K–Ge bond lengths are 3.41 Å. Ge is bonded to six equivalent K atoms to form a mixture of edge and corner-sharing GeK6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K6InAs3 by Materials Project

K6InAs3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are twelve inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to four As3- atoms to form a mixture of distorted edge and corner-sharing KAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.34–3.61 Å. In the second K1+ site, K1+ is bonded to four As3- atoms to form distorted KAs4 tetrahedra that share corners with four KKAs4 tetrahedra and edges with four KAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.37–3.64 Å. In the third K1+ site, K1+ is bonded in a 4-coordinate geometry to four As3- atoms. There are a spread of K–As bond distances ranging from 3.44–3.63 Å. In the fourth K1+ site, K1+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing KAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.36–3.47 Å. In the fifth K1+ site, K1+ is bonded to one K1+ and four As3- atoms to form a mixture of distorted edge and corner-sharing KKAs4 tetrahedra. The K–K bond length is 3.50 Å. There are a spread of K–As bond distances ranging from 3.36–3.73 Å. In the sixth K1+ site, K1+ is bonded to four As3- atoms to form a mixture of distorted edge and corner-sharing KAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.49–3.63 Å. In the seventh K1+ site, K1+ is bonded in a 6-coordinate geometry to two K1+ and four As3- atoms. The K–K bond length is 3.44 Å. There are a spread of K–As bond distances ranging from 3.41–3.81 Å. In the eighth K1+ site, K1+ is bonded to one K1+ and four As3- atoms to form a mixture of distorted edge and corner-sharing KKAs4 tetrahedra. The K–K bond length is 3.49 Å. There are a spread of K–As bond distances ranging from 3.38–3.72 Å. In the ninth K1+ site, K1+ is bonded in a 6-coordinate geometry to two K1+ and four As3- atoms. The K–K bond length is 3.44 Å. There are a spread of K–As bond distances ranging from 3.40–3.78 Å. In the tenth K1+ site, K1+ is bonded in a 4-coordinate geometry to four As3- atoms. There are a spread of K–As bond distances ranging from 3.33–3.65 Å. In the eleventh K1+ site, K1+ is bonded in a 3-coordinate geometry to one K1+ and four As3- atoms. There are a spread of K–As bond distances ranging from 3.42–3.93 Å. In the twelfth K1+ site, K1+ is bonded in a 4-coordinate geometry to one K1+ and four As3- atoms. There are a spread of K–As bond distances ranging from 3.42–3.86 Å. There are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded in a trigonal planar geometry to three As3- atoms. There are a spread of In–As bond distances ranging from 2.65–2.70 Å. In the second In3+ site, In3+ is bonded in a trigonal planar geometry to three As3- atoms. There are a spread of In–As bond distances ranging from 2.65–2.69 Å. There are six inequivalent As3- sites. In the first As3- site, As3- is bonded in a 9-coordinate geometry to eight K1+ and one In3+ atom. In the second As3- site, As3- is bonded in a 9-coordinate geometry to eight K1+ and one In3+ atom. In the third As3- site, As3- is bonded in a 9-coordinate geometry to eight K1+ and one In3+ atom. In the fourth As3- site, As3- is bonded in a 9-coordinate geometry to eight K1+ and one In3+ atom. In the fifth As3- site, As3- is bonded in a 9-coordinate geometry to eight K1+ and one In3+ atom. In the sixth As3- site, As3- is bonded in a 9-coordinate geometry to eight K1+ and one In3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2RbBi by Materials Project

RbK2Bi is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Rb is bonded in a 8-coordinate geometry to eight equivalent K and six equivalent Bi atoms. All Rb–K bond lengths are 3.82 Å. All Rb–Bi bond lengths are 4.41 Å. K is bonded to four equivalent Rb and four equivalent Bi atoms to form a mixture of distorted face, edge, and corner-sharing KRb4Bi4 tetrahedra. All K–Bi bond lengths are 3.82 Å. Bi is bonded in a body-centered cubic geometry to six equivalent Rb and eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Rb by Materials Project

RbK3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb is bonded to twelve K atoms to form a mixture of corner, edge, and face-sharing RbK12 cuboctahedra. There are four shorter (4.67 Å) and eight longer (4.86 Å) Rb–K bond lengths. There are two inequivalent K sites. In the first K site, K is bonded in a 12-coordinate geometry to four equivalent Rb and four equivalent K atoms. All K–K bond lengths are 4.67 Å. In the second K site, K is bonded in a square co-planar geometry to four equivalent Rb atoms.

36 MATERIALS SCIENCE↗