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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Apollo 16 neutron stratigraphy.

The Apollo 16 soils have the largest low-energy neutron fluences yet observed in lunar samples. Variations in the isotopic ratios Gd-158/Gd-157 and Sm-150/Sm-149 (up to 1.9 and 2.0%, respectively) indicate that the low-energy neutron fluence in the Apollo 16 drill stem increases with depth throughout the section sampled. Such a variation implies that accretion has been the dominant regolith 'gardening' process at this location. The data may be fit by a model of continuous accretion of pre-irradiated material or by models involving as few as two slabs of material in which the first slab could have been deposited as long as 1 b.y. ago. The ratio of the number of neutrons captured per atom by Sm to the number captured per atom by Gd is lower than in previously measured lunar samples, which implies a lower energy neutron spectrum at this site. The variation of this ratio with chemical composition is qualitatively similar to that predicted by Lingenfelter et al. (1972). Variations are observed in the ratio Gd-152/Gd-160 which are fluence-correlated and probably result from neutron capture by Eu-151.

Russ, G. P., III↗
NASA NTRS1979

Geochemical data synthesis and analysis

Data obtained at the Goddard Flight Center were collected for the purpose of completing analyses started at Goddard in order to maximize the scientific yield of the geochemistry program which was terminated in 1977. The major analytical task undertaken was to complete Gd analyses on a large number of samples already analyzed by mass spectrometry for other rare earth element abundances at Goddard. Gd values are important for pinning down the central part of the geochemically significant rare earth abundance pattern and are especially useful in the high precision definition of the utilitarian Eu anomaly. Isotope-dilution Gd abundances were obtained for 39 samples. The data are for 27 partition-coefficient samples, six Apollo 15 and 16 breccia samples, four terrestrial impactities, and associated rock standards.

Philpotts, J. A.↗
NASA NTRS1992

ROSAT guest investigator program (AO-1). On a search for coronal x ray emissions from white dwarfs

We have suggested that cool magnetic white dwarfs may be sources of X-ray coronal emission and proposed several prominent candidates for this emission. One of these candidates (EG 250) was approved for the C-category observation by the National and International Committee and was observed by ROSAT on April 17, 1991. Unfortunately, the granted exposure time (1071 s) was much shorter than that which was required by theoretical predictions to observe coronal X-ray emission from this object. The tape containing the data was send to us in November 1991. Since then we have analyzed the data visiting the ROSAT Science Center at NASA Goddard Space Flight Center. The analysis of the data taken during this short observation show, as expected, no X-rays. It is our hope that EG 250 will be observed again during the AO-2 phase of pointed observations, as 10,000 s of observing time was granted to V. Trimble for the C-category observation of this star. We have a close contact with Dr. Trimble regarding this matter. Because our all targets (GD 90, KUV 2316-123 and GD 356) proposed for the observation during the AO-2 phase of pointed observations have been approved by the National and International Committee, we have installed the required software at NASA/MSFC to be able to carry out the data analysis in Huntsville. Two of our targets have already been observed (KUV 2316-123 was observed on Dec. 3, 1991 with 10,000 s of the exposure time, and GD 356 was observed on Jan 4, 1992 with 5,000 s of the exposure time). We just received the data and will begin the analysis soon. The results of our analysis will be reported to the scientific community by publishing papers in the Astrophysical Journal Letters. Our intention is to submit a paper when the analysis of the data taken during AO2 is completed. The data taken during the observation of EG 250 will be a part of this paper.

Musielak, Z. E.↗
NASA NTRS1995

Quaternary borocarbides: New class of intermetallic superconductors

Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

Nagarajan, R.↗
NASA NTRS1995

ROSAT Pointed Observations of Cool Magnetic White Dwarfs

Observational evidence for the existence of a chromosphere on the cool magnetic white dwarf GD 356 has been reported. In addition, there has been theoretical speculations that cool magnetic white dwarfs may be sources of coronal X-ray emission. This emission, if it exists, would be distinct from the two types of X-ray emission (deep photospheric and shocked wind) that have already been observed from hot white dwarfs. We have used the PSPC instrument on ROSAT to observe three of the most prominent DA white dwarf candidates for coronal X-ray emission: GD 356, KUV 2316+123, and GD 90. The data show no significant emission for these stars. The derived upper limits for the X-ray luminosities provide constraints for a revision of current theories of the generation of nonradiative energy in white dwarfs.

Musielak, Z. E.↗
NASA NTRS1999

Probing porous media with gas diffusion NMR

We show that gas diffusion nuclear magnetic resonance (GD-NMR) provides a powerful technique for probing the structure of porous media. In random packs of glass beads, using both laser-polarized and thermally polarized xenon gas, we find that GD-NMR can accurately measure the pore space surface-area-to-volume ratio, S/V rho, and the tortuosity, alpha (the latter quantity being directly related to the system's transport properties). We also show that GD-NMR provides a good measure of the tortuosity of sandstone and complex carbonate rocks.

NASA Discipline Environmental Health↗
DOE OSTI2020

Materials Data on Gd2SeO2 by Materials Project

Gd2SeO2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Gd3+ is bonded in a 4-coordinate geometry to three equivalent Se2- and four equivalent O2- atoms. All Gd–Se bond lengths are 3.02 Å. There are one shorter (2.32 Å) and three longer (2.33 Å) Gd–O bond lengths. Se2- is bonded to six equivalent Gd3+ atoms to form distorted SeGd6 octahedra that share corners with twelve equivalent OGd4 tetrahedra, edges with six equivalent SeGd6 octahedra, and edges with six equivalent OGd4 tetrahedra. O2- is bonded to four equivalent Gd3+ atoms to form OGd4 tetrahedra that share corners with six equivalent SeGd6 octahedra, corners with six equivalent OGd4 tetrahedra, edges with three equivalent SeGd6 octahedra, and edges with three equivalent OGd4 tetrahedra. The corner-sharing octahedra tilt angles range from 27–48°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaGd2ZnO5 by Materials Project

BaGd2ZnO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.74–3.35 Å. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with five equivalent ZnO5 trigonal bipyramids, edges with two equivalent GdO7 pentagonal bipyramids, and an edgeedge with one ZnO5 trigonal bipyramid. There are a spread of Gd–O bond distances ranging from 2.35–2.41 Å. In the second Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.34–2.45 Å. Zn2+ is bonded to five O2- atoms to form distorted ZnO5 trigonal bipyramids that share corners with five equivalent GdO7 pentagonal bipyramids and an edgeedge with one GdO7 pentagonal bipyramid. There are a spread of Zn–O bond distances ranging from 2.01–2.17 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Ba2+, two Gd3+, and one Zn2+ atom to form a mixture of distorted edge and corner-sharing OBa3Gd2Zn octahedra. The corner-sharing octahedral tilt angles are 2°. In the second O2- site, O2- is bonded in a 6-coordinate geometry to two equivalent Ba2+, three Gd3+, and one Zn2+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, three Gd3+, and one Zn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd2TeO2 by Materials Project

Gd2TeO2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd3+ is bonded in a 4-coordinate geometry to four equivalent Te2- and four equivalent O2- atoms. All Gd–Te bond lengths are 3.48 Å. All Gd–O bond lengths are 2.29 Å. Te2- is bonded in a distorted body-centered cubic geometry to eight equivalent Gd3+ atoms. O2- is bonded to four equivalent Gd3+ atoms to form a mixture of corner and edge-sharing OGd4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GdPPt by Materials Project

GdPtP is hexagonal omega structure-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Gd3+ is bonded to six equivalent Pt2- and six equivalent P1- atoms to form a mixture of edge and face-sharing GdP6Pt6 cuboctahedra. All Gd–Pt bond lengths are 3.11 Å. All Gd–P bond lengths are 3.11 Å. Pt2- is bonded in a 9-coordinate geometry to six equivalent Gd3+ and three equivalent P1- atoms. All Pt–P bond lengths are 2.40 Å. P1- is bonded in a 9-coordinate geometry to six equivalent Gd3+ and three equivalent Pt2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd2Si2O7 by Materials Project

Gd2Si2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.32–2.60 Å. In the second Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Gd–O bond distances ranging from 2.29–2.64 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Gd3+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Gd3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Gd3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Gd3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two Gd3+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Gd3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to two Gd3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba5Gd8Zn4O21 by Materials Project

Ba5Gd8Zn4O21 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.68–3.27 Å. In the second Ba2+ site, Ba2+ is bonded in a distorted q6 geometry to ten O2- atoms. There are two shorter (2.91 Å) and eight longer (2.97 Å) Ba–O bond lengths. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with three GdO7 pentagonal bipyramids, corners with two equivalent ZnO5 trigonal bipyramids, edges with three equivalent GdO7 pentagonal bipyramids, edges with two equivalent ZnO5 trigonal bipyramids, and faces with two equivalent GdO7 pentagonal bipyramids. There are a spread of Gd–O bond distances ranging from 2.35–2.46 Å. In the second Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent GdO7 pentagonal bipyramids, corners with two equivalent ZnO5 trigonal bipyramids, edges with five GdO7 pentagonal bipyramids, an edgeedge with one ZnO5 trigonal bipyramid, and a faceface with one ZnO5 trigonal bipyramid. There are a spread of Gd–O bond distances ranging from 2.33–2.57 Å. Zn2+ is bonded to five O2- atoms to form distorted ZnO5 trigonal bipyramids that share corners with four GdO7 pentagonal bipyramids, edges with three GdO7 pentagonal bipyramids, and a faceface with one GdO7 pentagonal bipyramid. There are a spread of Zn–O bond distances ranging from 2.01–2.17 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, three Gd3+, and one Zn2+ atom. In the second O2- site, O2- is bonded in a 6-coordinate geometry to two Ba2+, three Gd3+, and one Zn2+ atom. In the third O2- site, O2- is bonded to four equivalent Ba2+, one Gd3+, and one Zn2+ atom to form a mixture of distorted edge and corner-sharing OBa4GdZn octahedra. The corner-sharing octahedral tilt angles are 7°. In the fourth O2- site, O2- is bonded to two equivalent Ba2+ and four equivalent Gd3+ atoms to form distorted corner-sharing OBa2Gd4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GdSO4F by Materials Project

GdSO4F crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Gd3+ is bonded in a 8-coordinate geometry to six O2- and two equivalent F1- atoms. There are a spread of Gd–O bond distances ranging from 2.37–2.61 Å. There are one shorter (2.25 Å) and one longer (2.26 Å) Gd–F bond lengths. S6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.46–1.51 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Gd3+ and one S6+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Gd3+ and one S6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one S6+ atom. F1- is bonded in a distorted linear geometry to two equivalent Gd3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd3OsO7 by Materials Project

Gd3OsO7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent OsO6 octahedra, corners with three equivalent GdO7 pentagonal bipyramids, edges with two equivalent OsO6 octahedra, and edges with two equivalent GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. There are a spread of Gd–O bond distances ranging from 2.26–2.63 Å. In the second Gd3+ site, Gd3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.35 Å) and four longer (2.69 Å) Gd–O bond lengths. Os5+ is bonded to six O2- atoms to form OsO6 octahedra that share corners with two equivalent OsO6 octahedra, corners with four equivalent GdO7 pentagonal bipyramids, and edges with four equivalent GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. There is two shorter (1.95 Å) and four longer (1.99 Å) Os–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Gd3+ and one Os5+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Gd3+ and two equivalent Os5+ atoms. In the third O2- site, O2- is bonded to four Gd3+ atoms to form a mixture of edge and corner-sharing OGd4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaGd2O4 by Materials Project

BaGd2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.75–2.99 Å. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing GdO6 octahedra. The corner-sharing octahedra tilt angles range from 50–60°. There are a spread of Gd–O bond distances ranging from 2.30–2.40 Å. In the second Gd3+ site, Gd3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing GdO6 octahedra. The corner-sharing octahedra tilt angles range from 50–60°. There are a spread of Gd–O bond distances ranging from 2.30–2.42 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Gd3+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Gd3+ atoms. In the third O2- site, O2- is bonded to two equivalent Ba2+ and three equivalent Gd3+ atoms to form distorted edge-sharing OBa2Gd3 square pyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Gd3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd3RuO7 by Materials Project

Gd3RuO7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent RuO6 octahedra, corners with three equivalent GdO7 pentagonal bipyramids, edges with two equivalent RuO6 octahedra, and edges with two equivalent GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 37°. There are a spread of Gd–O bond distances ranging from 2.24–2.54 Å. In the second Gd3+ site, Gd3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.35 Å) and four longer (2.68 Å) Gd–O bond lengths. Ru5+ is bonded to six O2- atoms to form RuO6 octahedra that share corners with two equivalent RuO6 octahedra, corners with four equivalent GdO7 pentagonal bipyramids, and edges with four equivalent GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. There is four shorter (1.97 Å) and two longer (1.98 Å) Ru–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Gd3+ and two equivalent Ru5+ atoms. In the second O2- site, O2- is bonded to four Gd3+ atoms to form a mixture of edge and corner-sharing OGd4 tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Gd3+ and one Ru5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd2TeO6 by Materials Project

Gd2TeO6 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. there are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.28–2.65 Å. In the second Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 hexagonal pyramids that share corners with three equivalent TeO6 octahedra, edges with two equivalent GdO7 hexagonal pyramids, and edges with two equivalent TeO6 octahedra. The corner-sharing octahedra tilt angles range from 39–45°. There are a spread of Gd–O bond distances ranging from 2.31–2.55 Å. Te6+ is bonded to six O2- atoms to form TeO6 octahedra that share corners with three equivalent GdO7 hexagonal pyramids and edges with two equivalent GdO7 hexagonal pyramids. There are a spread of Te–O bond distances ranging from 1.93–1.98 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Gd3+ and one Te6+ atom. In the second O2- site, O2- is bonded to three Gd3+ and one Te6+ atom to form distorted corner-sharing OGd3Te tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Gd3+ and one Te6+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one Te6+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one Te6+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Gd3+ and one Te6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba5Gd8Mn4O21 by Materials Project

Ba5Gd8Mn4O21 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.67–3.31 Å. In the second Ba2+ site, Ba2+ is bonded in a distorted q6 geometry to ten O2- atoms. There are two shorter (2.93 Å) and eight longer (2.99 Å) Ba–O bond lengths. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.31–2.61 Å. In the second Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share a cornercorner with one GdO7 pentagonal bipyramid, corners with two equivalent MnO5 trigonal bipyramids, edges with two equivalent MnO5 trigonal bipyramids, and faces with two equivalent GdO7 pentagonal bipyramids. There are a spread of Gd–O bond distances ranging from 2.34–2.49 Å. Mn2+ is bonded to five O2- atoms to form MnO5 trigonal bipyramids that share corners with two equivalent GdO7 pentagonal bipyramids and edges with two equivalent GdO7 pentagonal bipyramids. There are a spread of Mn–O bond distances ranging from 2.07–2.17 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, three Gd3+, and one Mn2+ atom. In the second O2- site, O2- is bonded in a 6-coordinate geometry to two Ba2+, three Gd3+, and one Mn2+ atom. In the third O2- site, O2- is bonded to four equivalent Ba2+, one Gd3+, and one Mn2+ atom to form a mixture of distorted edge and corner-sharing OBa4GdMn octahedra. The corner-sharing octahedral tilt angles are 7°. In the fourth O2- site, O2- is bonded to two equivalent Ba2+ and four equivalent Gd3+ atoms to form distorted corner-sharing OBa2Gd4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗