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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CeOF by Materials Project

CeOF is Matlockite structured and crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one CeOF sheet oriented in the (0, 0, 1) direction. Ce3+ is bonded in a 5-coordinate geometry to four equivalent O2- and one F1- atom. All Ce–O bond lengths are 2.33 Å. The Ce–F bond length is 2.38 Å. O2- is bonded to four equivalent Ce3+ atoms to form a mixture of corner and edge-sharing OCe4 tetrahedra. F1- is bonded in a single-bond geometry to one Ce3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeOF by Materials Project

CeOF is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ce3+ is bonded in a body-centered cubic geometry to four equivalent O2- and four equivalent F1- atoms. All Ce–O bond lengths are 2.45 Å. All Ce–F bond lengths are 2.45 Å. O2- is bonded to four equivalent Ce3+ atoms to form OCe4 tetrahedra that share corners with four equivalent FCe4 tetrahedra, corners with twelve equivalent OCe4 tetrahedra, and edges with six equivalent FCe4 tetrahedra. F1- is bonded to four equivalent Ce3+ atoms to form FCe4 tetrahedra that share corners with four equivalent OCe4 tetrahedra, corners with twelve equivalent FCe4 tetrahedra, and edges with six equivalent OCe4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeOF by Materials Project

CeOF crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ce3+ is bonded in a body-centered cubic geometry to four equivalent O2- and four equivalent F1- atoms. There are one shorter (2.36 Å) and three longer (2.38 Å) Ce–O bond lengths. There are three shorter (2.57 Å) and one longer (2.60 Å) Ce–F bond lengths. O2- is bonded to four equivalent Ce3+ atoms to form distorted OCe4 tetrahedra that share corners with six equivalent OCe4 tetrahedra, corners with ten equivalent FCe4 tetrahedra, edges with three equivalent OCe4 tetrahedra, and edges with three equivalent FCe4 tetrahedra. F1- is bonded to four equivalent Ce3+ atoms to form distorted FCe4 tetrahedra that share corners with six equivalent FCe4 tetrahedra, corners with ten equivalent OCe4 tetrahedra, edges with three equivalent OCe4 tetrahedra, and edges with three equivalent FCe4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeOF by Materials Project

CeOF crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce3+ is bonded in a body-centered cubic geometry to four equivalent O2- and four equivalent F1- atoms. All Ce–O bond lengths are 2.36 Å. All Ce–F bond lengths are 2.61 Å. O2- is bonded to four equivalent Ce3+ atoms to form distorted OCe4 tetrahedra that share corners with four equivalent OCe4 tetrahedra, corners with twelve equivalent FCe4 tetrahedra, edges with two equivalent FCe4 tetrahedra, and edges with four equivalent OCe4 tetrahedra. F1- is bonded to four equivalent Ce3+ atoms to form distorted FCe4 tetrahedra that share corners with four equivalent FCe4 tetrahedra, corners with twelve equivalent OCe4 tetrahedra, edges with two equivalent OCe4 tetrahedra, and edges with four equivalent FCe4 tetrahedra.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Observations on the long-period variability of the Gulf Stream downstream of Cape Hatteras

To examine the long-period variability of the Gulf Stream, sea level residuals relative to a 2-year mean sea level in the Gulf Stream downstream of Cape Hatteras (between 75 deg W and 60 deg W longitude) are used. Residuals, as derived from Geosat altimetry between November 1986 and December 1988, were gridded in space and time at a temporal resolution of 10 days and spatial resolution of 1/4 deg. Complex empirical orthogonal function (CEOF) analysis was applied to the data set to extract the spatially correlated signal with the original data subsampled to 1/2 deg. In addition to determining the space-time scales and propagation characterisitics of the different modes, wavenumber-frequency spectral techniques were used to separate the variability into propagating and stationary components. The CEOF technique applied to the data set indicated that the first four CEOF modes accounted for 60% of the variability and were found to be above the noise leve 99% of the time. CEOF 1 was associated with westward propagation at 5 km/d at a wavelength of 2000 km and eastward propagation at 1-2 km/d centered at a 500-km wavelength. This first CEOF is in good agreement with thin-jet equivalent barotropic models which predict westward propagation for wavelengths greater than 1130 km. A deflection of the wavelike pattern at 65 deg W also indicates a possible topographic effect. A simple scaling of the effect of topography indicates that for length scales longer than the internal Rossby radius of deformation, the topographic term is at least of the same order of magnitude as the beta effect. The second CEOF was more broadbanded in wavenumber space, with eastward propagation occurring in a wavenumber-frequency band between 300 and 1400 km and 0.5 and 2.0 cycles/yr. The third CEOF is similar in structure to the first, but with less energy. CEOF 4 was clearly identifiable with higher frequencies than the first three with westward propagation at 4 km/d. The spatial location of this mode along with the westward propagation indicates possible influences from eddy-stream interactions. Thus topography, Rossby wave dynamics and eddy-stream interactions all appear to have a significant role in determining the space-time scales and propagation properties of the long-period response of sea level in the Gulf Stream.

Vazquez, Jorge↗
NASA NTRS1987

The structure and evolution of seasonal wind anomalies over the near-equatorial eastern Indian and western Pacific Oceans

The longitude-height-time structure and evolution of near-equatorial wind variability over the eastern Indian and western Pacific Oceans are studied using data obtained from a network of eight radiosonde stations extending from southern India to the central Pacific Ocean. The seasonal zonal wind anomalies observed at the cross section beween Trivandrum and Majuro stations are analyzed using an empirical orthogonal function. The Walker Circulation fluctuations are described in terms of standing oscillations in the longitude-height plane, and it is determined that Southern Oscillation propagation anomaly best represents the wind fluctuations. A complex empirical orthogonal function (CEOF) analysis and an El Nino compositing methodology are applied to the seasonal zonal wind anomalies. It is determined that the composite El Nino anomalies correspond to the spatial structure and temporal evolution of anomalies implied by the CEOF analysis.

Gutzler, David S.↗