SEARCH · Engineering Papers

Results for “Ca”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Materials Data on Ca(Cu3O4)2 by Materials Project

Ca(Cu3O4)2 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ca2+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Ca–O bond lengths are 2.33 Å. Cu+2.33+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.92 Å. O2- is bonded to one Ca2+ and three equivalent Cu+2.33+ atoms to form a mixture of distorted edge and corner-sharing OCaCu3 trigonal pyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(TiS2)2 by Materials Project

Ca(TiS2)2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. Ca2+ is bonded to six S2- atoms to form CaS6 octahedra that share corners with six equivalent TiS6 octahedra, edges with two equivalent CaS6 octahedra, and edges with six TiS6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are four shorter (2.76 Å) and two longer (2.78 Å) Ca–S bond lengths. There are two inequivalent Ti3+ sites. In the first Ti3+ site, Ti3+ is bonded to six S2- atoms to form TiS6 octahedra that share corners with six equivalent CaS6 octahedra, edges with two equivalent CaS6 octahedra, and edges with six TiS6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are two shorter (2.44 Å) and four longer (2.49 Å) Ti–S bond lengths. In the second Ti3+ site, Ti3+ is bonded to six S2- atoms to form TiS6 octahedra that share edges with four equivalent CaS6 octahedra and edges with six TiS6 octahedra. There are four shorter (2.48 Å) and two longer (2.49 Å) Ti–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Ca2+ and three Ti3+ atoms to form a mixture of edge and corner-sharing SCa2Ti3 square pyramids. In the second S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Ti3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(AlH4)2 by Materials Project

Ca(AlH4)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ca2+ is bonded in a 10-coordinate geometry to ten H1- atoms. There are a spread of Ca–H bond distances ranging from 2.33–2.58 Å. Al3+ is bonded to six H1- atoms to form edge-sharing AlH6 octahedra. There are a spread of Al–H bond distances ranging from 1.68–1.83 Å. There are four inequivalent H1- sites. In the first H1- site, H1- is bonded in a distorted T-shaped geometry to one Ca2+ and two equivalent Al3+ atoms. In the second H1- site, H1- is bonded in a 1-coordinate geometry to two equivalent Ca2+ and one Al3+ atom. In the third H1- site, H1- is bonded in a 1-coordinate geometry to two equivalent Ca2+ and one Al3+ atom. In the fourth H1- site, H1- is bonded in a water-like geometry to two equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(CuAs)2 by Materials Project

Ca(CuAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca2+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Ca–As bond lengths are 3.19 Å. Cu2+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing CuAs4 tetrahedra. All Cu–As bond lengths are 2.47 Å. As3- is bonded in a 9-coordinate geometry to four equivalent Ca2+, four equivalent Cu2+, and one As3- atom. The As–As bond length is 2.64 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Ca2+ is bonded in a 12-coordinate geometry to twelve H+0.50+ atoms. There are a spread of Ca–H bond distances ranging from 2.29–2.75 Å. B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. There is one shorter (1.22 Å) and three longer (1.23 Å) B–H bond length. There are four inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to two equivalent Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(TmS2)2 by Materials Project

Ca(TmS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ca2+ is bonded to seven S2- atoms to form distorted CaS7 pentagonal bipyramids that share corners with eight TmS6 octahedra, edges with five TmS6 octahedra, edges with two equivalent CaS7 pentagonal bipyramids, and faces with two equivalent CaS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 14–67°. There are a spread of Ca–S bond distances ranging from 2.87–3.00 Å. There are two inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with four equivalent CaS7 pentagonal bipyramids, edges with six TmS6 octahedra, and an edgeedge with one CaS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 52–60°. There are a spread of Tm–S bond distances ranging from 2.68–2.79 Å. In the second Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with four equivalent CaS7 pentagonal bipyramids, edges with four TmS6 octahedra, and edges with four equivalent CaS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 52–60°. There are a spread of Tm–S bond distances ranging from 2.67–2.76 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Ca2+ and three Tm3+ atoms to form a mixture of distorted edge and corner-sharing SCa2Tm3 trigonal bipyramids. In the second S2- site, S2- is bonded to two equivalent Ca2+ and three Tm3+ atoms to form SCa2Tm3 square pyramids that share corners with two equivalent SCa3Tm2 square pyramids, corners with two equivalent SCa2Tm3 trigonal bipyramids, edges with five SCa2Tm3 square pyramids, and edges with three equivalent SCa2Tm3 trigonal bipyramids. In the third S2- site, S2- is bonded to three equivalent Ca2+ and two equivalent Tm3+ atoms to form a mixture of distorted edge and corner-sharing SCa3Tm2 square pyramids. In the fourth S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Tm3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(GaS2)2 by Materials Project

CaGa2S4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to seven S2- atoms to form distorted CaS7 pentagonal bipyramids that share corners with three equivalent CaS7 pentagonal bipyramids, corners with ten GaS4 tetrahedra, an edgeedge with one CaS7 pentagonal bipyramid, and edges with two GaS4 tetrahedra. There are a spread of Ca–S bond distances ranging from 2.87–3.13 Å. In the second Ca2+ site, Ca2+ is bonded to seven S2- atoms to form distorted CaS7 pentagonal bipyramids that share corners with three equivalent CaS7 pentagonal bipyramids, corners with six GaS4 tetrahedra, edges with two equivalent CaS7 pentagonal bipyramids, and edges with four GaS4 tetrahedra. There are a spread of Ca–S bond distances ranging from 2.89–3.10 Å. There are four inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with four CaS7 pentagonal bipyramids, corners with four GaS4 tetrahedra, and edges with two equivalent CaS7 pentagonal bipyramids. There are a spread of Ga–S bond distances ranging from 2.27–2.34 Å. In the second Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three CaS7 pentagonal bipyramids, corners with four GaS4 tetrahedra, and edges with two CaS7 pentagonal bipyramids. There are a spread of Ga–S bond distances ranging from 2.27–2.34 Å. In the third Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with six CaS7 pentagonal bipyramids, corners with two GaS4 tetrahedra, and an edgeedge with one GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.28–2.35 Å. In the fourth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three equivalent CaS7 pentagonal bipyramids, corners with two GaS4 tetrahedra, edges with two CaS7 pentagonal bipyramids, and an edgeedge with one GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.25–2.33 Å. There are eight inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ga3+ atoms. In the second S2- site, S2- is bonded to two Ca2+ and two Ga3+ atoms to form a mixture of distorted corner and edge-sharing SCa2Ga2 trigonal pyramids. In the third S2- site, S2- is bonded to two equivalent Ca2+ and two Ga3+ atoms to form a mixture of distorted corner and edge-sharing SCa2Ga2 tetrahedra. In the fourth S2- site, S2- is bonded to two equivalent Ca2+ and two Ga3+ atoms to form a mixture of distorted corner and edge-sharing SCa2Ga2 tetrahedra. In the fifth S2- site, S2- is bonded in a 3-coordinate geometry to one Ca2+ and two Ga3+ atoms. In the sixth S2- site, S2- is bonded in a 4-coordinate geometry to two Ca2+ and two Ga3+ atoms. In the seventh S2- site, S2- is bonded to two Ca2+ and two Ga3+ atoms to form a mixture of distorted corner and edge-sharing SCa2Ga2 trigonal pyramids. In the eighth S2- site, S2- is bonded in a distorted T-shaped geometry to one Ca2+ and two Ga3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ca(CO2)2 by Materials Project

CaC2O4 crystallizes in the monoclinic P2/m space group. The structure is two-dimensional and consists of one CaC2O4 sheet oriented in the (1, 0, 0) direction. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.23–2.56 Å. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.29–3.04 Å. There are four inequivalent C3+ sites. In the first C3+ site, C3+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.26 Å) and one longer (1.27 Å) C–O bond length. In the second C3+ site, C3+ is bonded in a bent 120 degrees geometry to two equivalent O2- atoms. Both C–O bond lengths are 1.27 Å. In the third C3+ site, C3+ is bonded in a bent 120 degrees geometry to two equivalent O2- atoms. Both C–O bond lengths are 1.27 Å. In the fourth C3+ site, C3+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.33 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Ca2+ and one C3+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one C3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ca2+ and one C3+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one C3+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ca2+, one C3+, and one O2- atom. The O–O bond length is 1.45 Å. In the sixth O2- site, O2- is bonded in a distorted L-shaped geometry to one Ca2+ and one O2- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Investigating the weak charge of 48 Ca using a dispersive optical model

A new nonlocal dispersive-optical-model analysis has been carried out for neutrons and protons in 48 Ca that reproduces the weak-form-factor measurement of CREX. In addition to elastic-scattering angular distributions, total and reaction cross sections, single-particle energies, the neutron and proton numbers, and the charge distribution, the CREX-measured weak form factor has been fit to extract the neutron and proton self-energies both above and below the Fermi energy. The resulting single-particle propagators yield a weak form factor of F w = 0.125 ± 0.05 and a neutron skin of R skin = 0.152 ± 0.05 fm, in good agreement with CREX. The rearrangement of the neutron distribution to accommodate such a thin neutron skin results in the high-momentum content of the neutrons exceeding that of the protons, in contrast to what is expected from high-energy two-nucleon knockout measurements by the CLAS collaboration and ab initio asymmetric matter calculations. The present analysis also emphasizes the importance of neutron experimental data in constraining weak charge observables necessary for a precise description of neutron densities. Notably, the neutron reaction cross section and further parity-violating experiments weak form factor measurements are essential to generate a unique way to determine the 48 Ca neutron distribution in this framework.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Final Report: Enhanced Algal Production of CA for Improved Atmospheric Delivery of CO2 To Ponds

Technologies that enable direct-air-capture (DAC) of CO2 and eliminate the need for a CO2 capture, storage, and distribution system would significantly reduce the cost of algal production, and greatly increase the volume of algae biomass that can be produced by enabling algae farms to be located anywhere. Such technologies include cultivation under high alkalinity/high pH conditions, which increase the driving force for CO2 absorption, and development of genetic tools and genetically engineered strains to decorate the surface of the algae with carbonic anhydrase (CA), enable secretion of CA by the algae, or more generally boost the performance of the carbon concentrating mechanism (CCM).

09 BIOMASS FUELS↗

DOE OSTI2021

Layered Transition Metal Oxides as Ca Intercalation Cathodes: A Systematic First-Principles Evaluation

Finding high-voltage Ca cathode materials is a critical step to unleashing the full potential of high-energy-density Ca-ion batteries. Therefore, first-principles calculations are used to demonstrate that P-type layered calcium transition metal (TM) oxide materials (CaTM 2 O 4 ) with a range of TM substitutions (TM = Ti, V, Cr, Mn, Fe, Co, and Ni) have excellent battery-related properties including thermodynamic stability, average voltage, energy density, synthesizability, ionic mobility, and electronic structure. However, the thermodynamic stability of the charged phase and TM redox activity are shown to be sensitive to TM selection, with CaCo 2 O 4 having the best balance of all considered properties. The utility of combining multiple TMs to expand the chemical search space for TM substitutions is demonstrated by mixing Co and Ni in layered CaTM 2 O 4 .

25 ENERGY STORAGE↗

DOE OSTI2020

Synthesis, Structural Characterization and Chemical Bonding of Sr 7 Li 6 Sn 12 and its Quaternary Derivatives with Eu and Alkaline Earth Metal (Mg, Ca, Ba) Substitutions. A Tale of Seven Li‐Containing Stannides and Two Complex Crystal Structures

In this paper, we discuss the synthesis and the structural characterization of the new ternary compound Sr 7 Li 6 Sn 12 and its six quaternary derivatives, where alkaline earth metals (Ca, Mg, Ba) and the rare earth metal Eu are substituted, yielding crystalline phases of monoclinic or orthorhombic symmetry. The title compounds were synthesized via high‐temperature solid‐state reactions of the corresponding elements. The crystal structures were determined by single‐crystal X‐ray diffraction methods. The (Sr,Ca) 7 Li 6 Sn 12 and Eu 7 (Mg,Li) 6 Sn 12 phases represent a new structure type (space group P 2/ m , No. 10) while Sr 7 Li 6 Sn 12 and the rest of the title phases crystallize in the orthorhombic base‐centered space group Cmmm (No. 65) which is similar to the Eu 7 Li 8– x Sn 10+ x ( x ≈ 2.0) phase with the Ce 7 Li 8 Ge 10 structure type (Pearson code oC 50). Careful examination of the resulting structures shows intricate disordering between Li and Sn atoms, which is governed by the total number of valence electrons. The discussion of experimental results is also supported by DFT electronic structure calculations.

Osman, Hussien H.↗

DOE OSTI2021

Coupling Thermomechanical Processing and Alloy Design to Improve Textures in Mg-Zn-Ca Sheet Alloys

Abstract The effect of Ca and Zn additions on the microstructure and texture evolution during thermomechanical processing of Mg-Zn-Ca sheet alloys was systematically investigated and quantified. Plane strain compression testing in a Gleeble thermomechanical simulator was used to physically simulate a 10-pass rolling schedule, while allowing for careful control and monitoring of the processing parameters. Textures in the as-deformed ternary alloy samples demonstrate a weak maximum basal intensity and spreading in the transverse direction. Increasing the Zn content to 3.2 wt.% in the ternary alloys resulted in samples that exhibited weak textures in the as-deformed state. Importantly, static recrystallization (SRX) during post-deformation annealing of these alloys promoted a desirable annular texture, with the c -axis tipped from the normal direction and a lower basal texture intensity. The evolution in texture during SRX is associated with as-deformed microstructures with broad grain orientation spreads and a low degree of recrystallization.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Chemical and environmental stability of monazite-cheralite solid solutions Ln 1-2 x Ca x Th x PO 4 (Ln = Pr, Nd; x = 0–0.15): A thermodynamic study

Monazite-cheralite ceramics are a promising waste form for actinides. To elucidate the long-term behavior of this matrix in aqueous solutions, this study measured thermodynamic data for Th-rhabdophanes Ln 1-2 x Ca x Th x PO 4 ·nH 2 O (with Ln = Pr, Nd; x = 0–0.15) and the associated anhydrous monazite-cheralites Ln 1-2 x Ca x Th x PO 4 . Further, solubility experiments at 298K and high temperature oxide melt solution calorimetry were combined for calculation of ΔG$^°_f$, ΔH$^°_f$ and S$^°_m$ of Th-rhabdophanes and associated monazite-cheralites. Standard solubility constants were employed in a geochemical simulation using the PHREEQC software, the results of which confirmed the high chemical stability of the monazite-cheralite phases and supported their use as a specific conditioning matrix for the long-term immobilization of actinides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Unraveling the nature of Fe-doping mediated inter- and intra-chain interactions in Ca 3 Co 2 O 6

The structural and magnetic properties of quasi-one-dimensional (1D) spin-chain compounds Ca 3 Co 2-x Fe x O 6 (x = 0, 0.1, 0.2 and 0.3) synthesized by a sol-gel method have been systematically studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), neutron powder diffraction (NPD), dc and ac magnetization measurements. The samples adopt a rhombohedral crystal structure with the space group R-3c in a temperature range of 5–100 K. Fe ions are found to locate at the trigonal prism Co2 crystallographic sites. Fe doping converts some of low-spin Co 3+ ions at Co1 octahedral sites into Co 2+ ions. For the high-temperature paramagnetic phase, the Curie paramagnetic temperature θp changes its sign from positive to negative at x = 0.2, implying that the dominant magnetic interaction is driven from ferromagnetic (FM) to antiferromagnetic (AFM) upon Fe substitution. A partial low-spin to high-spin state crossover of the Co1 ions is observed at high Fe-doping level x = 0.3. All the samples exhibit a long-range spin-density wave (SDW) AFM ordering below TN, followed by a spin-glass-like transition at Tf. These low-temperature magnetic phases were significantly suppressed upon Fe doping. The Fe substitution in Ca 3 Co 2-x Fe x O 6 weakened both intrachain and interchain magnetic interactions, caused by enhanced magnetic disorder due to the different magnetic characters of Ising Co and Heisenberg Fe spins.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Nickel B-site substitution in bulk Sr 1-x Ca x FeO 3 perovskite oxygen carriers: Benefits and limitations

We report oxygen (O 2 ) storage materials often rely on the presence of cobalt (Co) to reduce the thermodynamic penalty and increase the kinetics necessary for efficient O 2 storage and release. In this work, we investigate nickel (Ni) as an alternative B-site dopant in Sr 1-x Ca x FeO 3 to identify Co-free carriers that still show improved kinetics at low temperatures. In fact, we show a substantial increase in the reversible O2 release rate through mild Ni B-site substitution (y = 0.06) in select Sr 1-x Ca x Fe 1-y Ni y O 3 systems at 400 to 500 °C, reaching 2.00 wt.% O 2 release up to approximately 75% faster than Ni-free systems. To explain the role of Ni in these systems, we use density functional theory to calculate the O 2 vacancy (V O ) formation energy from separate metal-oxygen (M-O) bonding and relaxation components. We computationally show elongated Ni-O bonds are directly responsible for the decrease in V O upon Ni substitution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Single crystal growth and characterization of new Zintl phase Ca 9 Zn 3.1 In 0.9 Sb 9

Complex Zintl phases have yielded a large variety of promising new thermoelectric materials. Here we report the discovery of the new Zintl phase Ca 9 (Zn 1– x In x ) 4 Sb 9 ( x ~ 0.9), needle-like crystals of which were serendipitously obtained from an In- and Sb-rich flux. Although its composition is reminiscent of Ca 9 Zn 4+ x Sb 9 , an excellent thermoelectric material with zT > 1, the substitution of In on the Zn site leads to the formation of an entirely new structure type. Single crystal X-ray diffraction revealed a structure characterized by T Sb 4 tetrahedra ( T = statistically disordered Zn and In atoms) and ZnSb 3 triangular units, which share common corners to form [ T 4 Sb 9 ] 18– polyanions. The average structure was found to have hexagonal symmetry. The valence electron count in this heavily-disordered structure appears to follows the Zintl-Klemm rules, suggesting semiconducting behavior. Single crystal electrical conductivity and Seebeck coefficient measurements support this conclusion, suggesting that the as-grown crystals are degenerate p -type semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

The 12-layer trimer-based hexagonal perovskite Cs 4 Ca 0.7 Mn 3.3 Cl 12

Here, we describe the crystal structure and basic magnetic properties of Cs 4 Ca 0.7 Mn 3.3 Cl 12 , a previously unreported twelve layer (12L-) hexagonal (R-3m) chloride perovskite. Its crystal structure features face sharing MnCl 6 octahedra that form Mn 3 Cl 12 trimers. The trimers, which form a triangular array, are separated by corner sharing to layers of disordered single Ca(Mn)Cl 6 octahedra. The decreased intratrimer Mn–Mn distance yields stronger magnetic coupling within trimers than between trimers. The dominant magnetic interactions are antiferromagnetic (θ CW = –105 K), the effective magnetic moment per Mn 2+ is 6.5 μ B , and potential signatures of magnetic frustration are observed. Behavior consistent with short- and long-range magnetic order is exhibited at approximately 37 and 0.7 K, respectively.

12L-hexagonal perovskite↗