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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Optimized in situ crystal growth and disordered quasi-one-dimensional magnetism in Li 2 Mn 2 ( MoO 4 ) 3

We present that the quasi-one-dimensional structure of Li 2 Mn 2 ( MoO 4 ) 3 consists of three mutually distinct chains of Li 1 - x Mn x -centered polyhedra in which Mn ostensibly adopts a J = 5 / 2 Mn 2 + configuration. In situ x-ray scattering experiments carried out as crystallites emerge from a molten oxide solution facilitate the synthesis of large single crystals. Ex situ x-ray diffraction finds no evidence of long-range Li/Mn occupancy ordering, suggesting that the structure is effectively composed of finite chains of Mn moments of statistically varying lengths. UV/visible diffuse reflectance spectroscopy measurements establish a wide 3.43(12)-eV direct charge gap consistent with the local polyhedral coordination of the nominally Mn 2 + species. The temperature T dependence of the DC magnetic susceptibility χ reveals a fluctuating moment of only 2.74 μ B ± 0.01 μ B /Mn, dramatically reduced from the 5.9 μ B /Mn expected for Mn 2 + . Meanwhile, the Weiss temperature Θ W = - 89 ± 1 K reveals antiferromagnetic fluctuations that are stymied from reaching an ordered state apparently by the chemical disorder intrinsic to the polyhedral chains. Measurements of magnetization vs field H at T ≤ 10 K are far from saturation even at H = 5 T and are strongly non-Brillouin-like, instead scaling as H / T 0.24 ( 3 ) and suggesting the presence of quantum fluctuations associated with an eventual quasi-one-dimensional, disordered magnetic phase.

1-dimensional systems↗
DOE OSTI2020

Large anomalous Nernst and inverse spin-Hall effects in epitaxial thin films of kagome semimetal Mn 3 Ge

Synthesis of crystallographically well-defined thin films of topological materials is important for unraveling their mesoscale quantum properties and for device applications. Mn 3 Ge , an antiferromagnetic Weyl semimetal with a chiral magnetic structure on a kagome lattice, is expected to have enhanced Berry curvature around Weyl nodes near the Fermi energy, leading to large anomalous Hall/Nernst effects and a large spin-Hall effect. Using magnetron sputtering, we have grown epitaxial thin films of hexagonal D 0 19 Mn 3 Ge that are flat and continuous. Large anomalous Nernst and inverse spin-Hall effects are observed in thermoelectric and spin-pumping devices. The anomalous Nernst signal in our Mn 3 Ge films is estimated to be 0.1 μV/K and is comparable to that in ferromagnetic Fe, despite Mn 3 Ge having a weak magnetization of ~ 3.5 m μ B / Mn at room temperature. In this work, the spin-mixing conductance is 90.5 nm – 2 at the Py / Mn 3 Ge interface, and the spin-Hall angle in Mn 3 Ge is estimated to be about eight times of that in Pt.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Durable Mn-Based PGM-Free Catalysts for Polymer Electrolyte Membrane Fuel Cells

This proposed project aims to develop and evaluate novel manganese based, nitrogen-derived, PGM-free electrocatalysts (denoted as Mn-N-C) to fully address the membrane electrolyte assemblies (MEA)’s ionomer degradation issue resulting from iron. Four thrusts will be pursed in this proposed project. First, advanced first-principles computation methods will be employed to accelerate the rational catalyst design and synthesis. Second, an effective hydro-gel method will be used to maximize atomic Mn active sites embedded in carbon matrix. Next, state-of-the art methods in fuel cell companies will be used to fabricate MEAs containing the Mn-N-C catalysts. Finally, industry standards will be rigorously followed to evaluate fuel cell performance and durability of the Mn-N-C catalysts. With successful completion of the project, it is expected that the following outcomes will be achieved. (1) A set of MEAs containing the Mn-N-C catalysts and with active area large than 50 cm 2 for independent testing, (2) testing results demonstrating that the MEAs of Mn-N-C catalysts have mass activity of 0.044 A/cm 2 at 0.9 VIR-free and H 2 /air performance of 0.50 V at 1.0 A/cm 2 ; (3) fundamental understanding of the composition-structure-property relation of the PGM-free Mn- N-C catalysts, and (4) computational data, measurement data, and publications deposited into the database of ElectroCat Consortium.

08 HYDROGEN↗
DOE OSTI2024

Characterization of Mn 5 Ge 3 Contacts on a Shallow Ge/SiGe Heterostructure

Mn 5 Ge 3 is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of Mn 5 Ge 3 -based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of Mn 5 Ge 3 -based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct Mn 5 Ge 3 -based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that Mn 5 Ge 3 -based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of 0.10 eV (extracted from a Mn 5 Ge 3 /n-Ge analogue) and a contact resistance in the order of 1 kΩ. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Microstructural Engineering of Mn-Alloyed Austenitic Steel for Hydrogen Storage and Delivery

Austenitic stainless steels are commonly used for hydrogen storage and transportation. These alloys have a high nickel (Ni) content, which increases alloy cost. In this study, high manganese (Mn) austenitic alloys were evaluated as potential lower cost alternatives. Two heats of high Mn alloys with different stacking fault energies (SFE) of ~29 mJ·m -2 and 49 mJ·m -2 were acquired. Additionally, a new vanadium (V)-microalloyed high Mn alloy was designed to achieve a SFE of 47 mJ·m -2 to minimize planar slip deformation mechanisms. Post-processing via cold working in conjunction with aging was also performed on the V-microalloyed high Mn steel. Hydrogen embrittlement sensitivity was investigated using circumferential notch tensile specimens cathodically charged with hydrogen in a 0.05M NaOH electrolytic solution. The alloys were compared to a cold-worked 316L stainless steel, which exhibited no strength loss due to hydrogen. The high Mn alloys with SFE of ~29 mJ·m 2 and 49 mJ·m -2 had notch strength losses of 11 and 6 pct, respectively. The V-microalloyed high Mn steel in the as-hot-rolled condition had a notch strength loss of 17 pct. Furthermore, the V-microalloyed high Mn steel in the cold worked and aged condition indicated no notch strength loss in hydrogen, which was comparable to the performance of the 316L stainless steel.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(GaS2)2 by Materials Project

MnGa2S4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with ten GaS4 tetrahedra and edges with three MnS6 octahedra. There are a spread of Mn–S bond distances ranging from 2.55–2.66 Å. In the second Mn2+ site, Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with eight GaS4 tetrahedra and edges with five MnS6 octahedra. There are a spread of Mn–S bond distances ranging from 2.54–2.74 Å. In the third Mn2+ site, Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with ten GaS4 tetrahedra and edges with three MnS6 octahedra. There are a spread of Mn–S bond distances ranging from 2.56–2.67 Å. In the fourth Mn2+ site, Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with six GaS4 tetrahedra and edges with six MnS6 octahedra. There are a spread of Mn–S bond distances ranging from 2.54–2.61 Å. In the fifth Mn2+ site, Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with six GaS4 tetrahedra and edges with six MnS6 octahedra. There are a spread of Mn–S bond distances ranging from 2.51–2.62 Å. In the sixth Mn2+ site, Mn2+ is bonded to six S2- atoms to form MnS6 octahedra that share corners with eight GaS4 tetrahedra and edges with five MnS6 octahedra. There are a spread of Mn–S bond distances ranging from 2.54–2.72 Å. There are twelve inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three MnS6 octahedra and corners with six GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–62°. There are a spread of Ga–S bond distances ranging from 2.22–2.36 Å. In the second Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with four MnS6 octahedra and corners with five GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–63°. There are a spread of Ga–S bond distances ranging from 2.26–2.38 Å. In the third Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with four MnS6 octahedra and corners with five GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–63°. There are a spread of Ga–S bond distances ranging from 2.26–2.38 Å. In the fourth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three MnS6 octahedra and corners with six GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–63°. There are a spread of Ga–S bond distances ranging from 2.22–2.36 Å. In the fifth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with five MnS6 octahedra, corners with three GaS4 tetrahedra, and an edgeedge with one GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Ga–S bond distances ranging from 2.25–2.34 Å. In the sixth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three MnS6 octahedra and corners with six GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–63°. There are a spread of Ga–S bond distances ranging from 2.22–2.36 Å. In the seventh Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with five MnS6 octahedra, corners with three GaS4 tetrahedra, and an edgeedge with one GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Ga–S bond distances ranging from 2.25–2.34 Å. In the eighth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with five MnS6 octahedra, corners with three GaS4 tetrahedra, and an edgeedge with one GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Ga–S bond distances ranging from 2.25–2.34 Å. In the ninth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with five MnS6 octahedra, corners with three GaS4 tetrahedra, and an edgeedge with one GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Ga–S bond distances ranging from 2.25–2.34 Å. In the tenth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with four MnS6 octahedra and corners with five GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–63°. There are a spread of Ga–S bond distances ranging from 2.26–2.38 Å. In the eleventh Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with four MnS6 octahedra and corners with five GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–63°. There are a spread of Ga–S bond distances ranging from 2.26–2.38 Å. In the twelfth Ga3+ site, Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with three MnS6 octahedra and corners with six GaS4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–62°. There are a spread of Ga–S bond distances ranging from 2.22–2.36 Å. There are twenty-four inequivalent S2- sites. In the first S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the second S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the third S2- site, S2- is bonded in a distorted trigonal planar geometry to one Mn2+ and two Ga3+ atoms. In the fourth S2- site, S2- is bonded to three Mn2+ and one Ga3+ atom to form a mixture of distorted corner and edge-sharing SMn3Ga trigonal pyramids. In the fifth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the sixth S2- site, S2- is bonded to three Mn2+ and one Ga3+ atom to form a mixture of distorted corner and edge-sharing SMn3Ga trigonal pyramids. In the seventh S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the eighth S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Mn2+ and one Ga3+ atom. In the ninth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the tenth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the eleventh S2- site, S2- is bonded in a 4-coordinate geometry to two Mn2+ and two Ga3+ atoms. In the twelfth S2- site, S2- is bonded to three Mn2+ and one Ga3+ atom to form a mixture of distorted corner and edge-sharing SMn3Ga trigonal pyramids. In the thirteenth S2- site, S2- is bonded in a 4-coordinate geometry to two Mn2+ and two Ga3+ atoms. In the fourteenth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the fifteenth S2- site, S2- is bonded to three Mn2+ and one Ga3+ atom to form a mixture of distorted corner and edge-sharing SMn3Ga trigonal pyramids. In the sixteenth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Ga3+ atoms. In the seventeenth S2- site, S2- is bonded in a trigonal planar geometry to one Mn2+ and two Ga3+ atoms. In the eighteenth S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Mn2+ and one Ga3+ atom. In the nineteenth S2- site, S2- is bonded in a distorted trigonal planar geometry to one Mn2+ and two Ga3+ atoms. In the twentieth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Mn2+ and one Ga3+ atom. In the twenty-first S2- site, S2- is bonded in a rectangular see-saw-like geometry to three Mn2+ and one Ga3+ atom. In the twenty-second S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Ga3+ atoms. In the twenty-third S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the twenty-fourth S2- site, S2- is bonded in a distorted trigonal planar geometry to one Mn2+ and two Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(NO3)4 by Materials Project

Mn(NO3)4 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four Mn(NO3)4 clusters. In two of the Mn(NO3)4 clusters, Mn4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Mn–O bond distances ranging from 2.01–2.50 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.34 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.32 Å. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.35 Å. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.32 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted L-shaped geometry to one Mn4+ and one N5+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Mn4+ and one N5+ atom. In the fifth O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a distorted L-shaped geometry to one Mn4+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the ninth O2- site, O2- is bonded in an L-shaped geometry to one Mn4+ and one N5+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the eleventh O2- site, O2- is bonded in an L-shaped geometry to one Mn4+ and one N5+ atom. In the twelfth O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In two of the Mn(NO3)4 clusters, Mn4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Mn–O bond distances ranging from 2.02–2.44 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.34 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.34 Å. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.32 Å. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.32 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the second O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In the third O2- site, O2- is bonded in a distorted L-shaped geometry to one Mn4+ and one N5+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the fifth O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a distorted L-shaped geometry to one Mn4+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a water-like geometry to one Mn4+ and one N5+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to one Mn4+ and one N5+ atom. In the twelfth O2- site, O2- is bonded in a distorted L-shaped geometry to one Mn4+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(BH4)2 by Materials Project

Mn(BH4)2 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are five inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to eight H+0.50+ atoms to form distorted MnH8 hexagonal bipyramids that share edges with four BH4 tetrahedra. There are a spread of Mn–H bond distances ranging from 2.02–2.15 Å. In the second Mn2+ site, Mn2+ is bonded to eight H+0.50+ atoms to form distorted MnH8 hexagonal bipyramids that share edges with four BH4 tetrahedra. There are a spread of Mn–H bond distances ranging from 2.02–2.14 Å. In the third Mn2+ site, Mn2+ is bonded to eight H+0.50+ atoms to form distorted MnH8 hexagonal bipyramids that share edges with four BH4 tetrahedra. There are a spread of Mn–H bond distances ranging from 2.02–2.15 Å. In the fourth Mn2+ site, Mn2+ is bonded in a 8-coordinate geometry to eight H+0.50+ atoms. There are a spread of Mn–H bond distances ranging from 2.04–2.24 Å. In the fifth Mn2+ site, Mn2+ is bonded in a 8-coordinate geometry to eight H+0.50+ atoms. There are a spread of Mn–H bond distances ranging from 2.03–2.25 Å. There are ten inequivalent B3- sites. In the first B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share an edgeedge with one MnH8 hexagonal bipyramid. There are a spread of B–H bond distances ranging from 1.22–1.24 Å. In the second B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share an edgeedge with one MnH8 hexagonal bipyramid. There are a spread of B–H bond distances ranging from 1.22–1.24 Å. In the third B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with two equivalent MnH8 hexagonal bipyramids. There is two shorter (1.23 Å) and two longer (1.24 Å) B–H bond length. In the fourth B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with two MnH8 hexagonal bipyramids. There is two shorter (1.23 Å) and two longer (1.24 Å) B–H bond length. In the fifth B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with two MnH8 hexagonal bipyramids. There is two shorter (1.23 Å) and two longer (1.24 Å) B–H bond length. In the sixth B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with two equivalent MnH8 hexagonal bipyramids. There is two shorter (1.23 Å) and two longer (1.24 Å) B–H bond length. In the seventh B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with two MnH8 hexagonal bipyramids. All B–H bond lengths are 1.23 Å. In the eighth B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with two equivalent MnH8 hexagonal bipyramids. All B–H bond lengths are 1.23 Å. In the ninth B3- site, B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. All B–H bond lengths are 1.23 Å. In the tenth B3- site, B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. All B–H bond lengths are 1.23 Å. There are thirty-five inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Mn2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Mn2+ and one B3- atom. In the fifth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Mn2+ and one B3- atom. The H–B bond length is 1.22 Å. In the sixth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the seventh H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the eighth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. The H–B bond length is 1.24 Å. In the ninth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the tenth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the eleventh H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. The H–B bond length is 1.22 Å. In the twelfth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the thirteenth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the fourteenth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the fifteenth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Mn2+ and one B3- atom. In the sixteenth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Mn2+ and one B3- atom. In the seventeenth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Mn2+ and one B3- atom. In the eighteenth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the nineteenth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twentieth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-first H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-second H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-third H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-fourth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-fifth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-sixth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-seventh H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-eighth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the twenty-ninth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the thirtieth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Mn2+ and one B3- atom. In the thirty-first H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Mn2+ and one B3- atom. In the thirty-second H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Mn2+ and one B3- atom. In the thirty-third H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the thirty-fourth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom. In the thirty-fifth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Mn2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(BO4)4 by Materials Project

MnO5(B4O10)O is alpha Niobium phosphide structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two (B4O10)O clusters and two MnO5 clusters. In each (B4O10)O cluster, there are four inequivalent B sites. In the first B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.31–1.42 Å. In the second B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.35–1.45 Å. In the third B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.33–1.45 Å. In the fourth B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.32–1.46 Å. There are eleven inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.33 Å. In the second O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.35 Å. In the third O site, O is bonded in a single-bond geometry to one B atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to two B atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two B atoms. In the sixth O site, O is bonded in a single-bond geometry to one B and one O atom. In the seventh O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the eighth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.33 Å. In the ninth O site, O is bonded in a bent 150 degrees geometry to two B atoms. In the tenth O site, O is bonded in a distorted single-bond geometry to one B and one O atom. In the eleventh O site, O is bonded in a distorted single-bond geometry to one B and one O atom. In each MnO5 cluster, Mn is bonded in a distorted tetrahedral geometry to four O atoms. There are a spread of Mn–O bond distances ranging from 1.59–1.80 Å. There are five inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two O atoms. Both O–O bond lengths are 1.46 Å. In the second O site, O is bonded in a distorted single-bond geometry to one Mn and one O atom. In the third O site, O is bonded in a distorted single-bond geometry to one Mn and one O atom. In the fourth O site, O is bonded in a single-bond geometry to one Mn atom. In the fifth O site, O is bonded in a single-bond geometry to one Mn atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Decoding Li + /Na + Exchange Route Toward High-Performance Mn-Based Layered Cathodes for Li-Ion Batteries

Li + /Na + exchange has been extensively explored as an effective method to prepare high-performance Mn-based layered cathodes for Li-ion batteries, since the first report in 1996 by P. G. Bruce (Nature, 1996. 381, 499–500). Understanding the detailed structural changes during the ion-exchange process is crucial to implement the synthetic control of high-performance layered Mn-based cathodes, but less studied. Herein, in situ synchrotron X-ray diffraction, density functional theory calculations, and electrochemical tests are combined to conduct the systemic studies into the structural changes during the ion-exchange process of an Mn-only layered cathode O3-type Li 0.67 [Li 0.22 Mn 0.78 ]O 2 (LLMO) from the corresponding counterpart P3-type Na 0.67 [Li 0.22 Mn 0.78 ]O 2 (NLMO). The temperature-resolved observations combined with theoretical calculations reveal that the Li + /Na + exchange is favorable thermodynamically and composited with two tandem topotactic phase transitions: 1) from NLMO to a layered intermediate through ≈60% of Li + /Na + exchange. 2) then to the final layered product LLMO through further Li insertion. Moreover, the intermediate-dominate composite is obtained by slowing down the exchange kinetics below room temperature, showing better electrochemical performance than LLMO obtained by the traditional molten-salt method. Finally, the findings provide guides for the synthetic control of high-performance Mn-based cathodes under mild conditions.

25 ENERGY STORAGE↗
DOE OSTI2022

Deciphering the Mechanistic Role of Individual Oxide Phases and Their Combinations in Supported Mn–Na 2 WO 4 Catalysts for Oxidative Coupling of Methane

Oxidative coupling of methane (OCM) is an attractive direct route for upgrading methane to valuable chemicals. In this study, Temporal Analysis of Products (TAP) and steady state experiments are conducted to understand the role of individual oxide phases and their combinations in supported Mn-Na 2 WO 4 /SiO 2 catalysts for OCM. The results from TAP transient kinetic studies indicate that Mn plays an important role in promoting gas phase oxygen activation, while NaO x /SiO 2 and WO x /SiO 2 are relatively inert towards gas phase oxygen and methane activation. However, the supported catalyst combining Na and W in the form Na 2 WO 4 show enhanced gas phase oxygen activation exhibiting a much lower oxygen activation energy (148 kJ/mol) and enhanced activity toward methane activation as compared to the individual supported oxide catalysts. Addition of Mn to Na 2 WO 4 /SiO 2 further decreases the oxygen activation energy by 40 kJ/mol. Moreover, methane activation is also enhanced with CH 3 as the main intermediate but, with increasing Mn content, more CH 2 intermediates are observed. Different forms of oxygen (both dioxygen and atomic) are detected on the catalyst surface using isotopic pump/probe pulsing and their distribution is found to depend on the catalyst composition. An optimal Mn content in the Na 2 WO 4 /SiO 2 catalyst system is needed to enhance the amount of dioxide surface species (e.g., superoxide 16 O 2 - or peroxide 16 O 2 2- ) associated with the Na 2 WO 4 leading to high C 2 selectivity for OCM. When the Mn content is too high, the larger MnOx domains are shown to contribute to the formation of higher concertation of monoxide surface species that lead to nonselective OCM pathways. This insight from transient kinetic characterization using TAP combined with conventional steady state studies, provides a deeper understanding of the role of individual oxide phases and their combination on supported catalysts toward the formation of intermediate surface species and their impact on the OCM reaction mechanism. This knowledge is critical toward designing superior catalyst formulations for OCM.

10 SYNTHETIC FUELS↗
DOE OSTI2024

Role of Exciton Diffusion in the Efficiency of Mn Dopant Emission in Two-Dimensional Perovskites

Two-dimensional (2D) metal-halide perovskites have promising characteristics for optoelectronic applications. By incorporating Mn 2+ ions into the perovskite structure, improved photoluminescence quantum yield can be achieved. This has been attributed to the formation of defect states that act as efficient recombination centers. Here, we make use of transient photoluminescence microscopy to characterize important material parameters of Mn 2+ -doped 2D perovskites with different doping levels. From these measurements, we visualize the importance of exciton transport as an intermediate step in the excitation of Mn 2+ . We model the spatiotemporal dynamics of the excited states to extract the diffusion constant and the transfer rate of the excitations to the Mn dopant sites. Interestingly, from these models, we find that the average distance an exciton needs to travel before transferring to a Mn site is significantly larger than expected from the Mn concentration obtained from elemental analysis. These insights are critical from a device design perspective.

2D perovskites↗
DOE OSTI2026

Toward Tunable Magnetic Dirac Semimetals: Mn Doping of Cd 3 As 2

Magnetic impurities provide a route toward increasing functionality in electronic materials, often enabling new device concepts and architectures. In the case of topological semimetals, dilute magnetic doping presents a particularly attractive approach for inducing a Dirac to Weyl phase change via time reversal symmetry breaking. However, efforts to realize changes in the electronic structure have been limited by challenges in incorporating magnetic impurities into crystals with sufficiently high electron mobilities to detect them via transport or spectroscopic techniques. Here, we demonstrate incorporation of Mn into Cd 3 ⁢As 2 Dirac semimetal thin films grown by molecular beam epitaxy (MBE). Using As-rich growth conditions and [001] oriented thin films, Mn compositions of >10% are achieved. Films contain uniform distributions of Mn with no evidence of secondary phases and exhibit electron mobilities greater than 10 000–30 000 cm 2 /Vs up to 5% Mn. An evolution in the magnetization behavior along with the emergence of a second quantum oscillation frequency at low Mn concentrations provide preliminary evidence of Mn-induced changes in the electronic structure that are consistent with a Weyl phase. This work demonstrates the potential of magnetically doping topological semimetal thin films and a pathway for synthesizing them.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Chloride facilitates Mn(III) formation during photoassembly of the Photosystem II oxygen-evolving complex

The Mn 4 Ca oxygen-evolving complex (OEC) in Photosystem II (PSII) is assembled in situ from free Mn 2+ , Ca 2+ , and water. In an early light-driven step, Mn 2+ in a protein high-affinity site is oxidized to Mn 3+ . Using dual-mode electron paramagnetic resonance spectroscopy, we observed that Mn 3+ accumulation increases as chloride concentration increases in spinach PSII membranes depleted of all extrinsic subunits. At physiologically relevant pH values, this effect requires the presence of calcium. Here, when combined with pH studies, we conclude that the first Mn 2+ oxidation event in OEC assembly requires a deprotonation that is facilitated by chloride.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Effect of glutathione-coated Mn-doped ZnS quantum dots on nutrient delivery in basil ( Ocimum basilicum ) plants

Ensuring efficient nutrient delivery while minimizing environmental impacts remains a significant challenge for modern agriculture. Nanotechnology-based fertilizers offer promising strategies to improve nutrient uptake and bioavailability in plants. This research aims to evaluate the use of Glutathione-coated Manganese-doped Zinc Sulfide quantum dots (GSH-ZnS-Mn QDs) as a potential nano fertilizer for basil (Ocimum basilicum). QDs' physicochemical properties were characterized using UV–Vis spectroscopy, photoluminescence, FTIR, and energy-dispersive X-ray spectroscopy, confirming successful Mn doping and glutathione surface functionalization. Basil plants were exposed to different concentrations of GSH-ZnS-Mn QDs under soil and hydroponic conditions. Plant growth parameters, oxidative stress responses, photosynthetic pigments, and macro- and micronutrient uptake were assessed using biochemical assays and inductively coupled plasma optical emission spectrometry (ICP-OES). Elemental uptake, spatial distribution, and zinc speciation were further investigated using synchrotron-based micro-X-ray fluorescence (μ-XRF) imaging and X-ray absorption near-edge structure (XANES) spectroscopy. Results show that exposure to GSH-ZnS-Mn QDs resulted in a concentration-dependent increase in leaf and stem biomass, accompanied by enhanced Zn accumulation in plant tissues. Catalase activity decreased across all tested concentrations, suggesting a shift toward glutathione-dependent antioxidant pathways rather than oxidative damage. Chlorophyll levels exhibited moderate reductions at higher concentrations. The higher increase in macronutrient (K, Ca, and Mg) uptake was reported in plants exposed to 200 ppm of QDs. μ-XRF imaging indicated a selective accumulation of Zn in roots and stems, with partial translocation to leaves. XANES analyses revealed that Zn from QDs was mainly converted into organic Zn species, such as Zn-phytate, Zn-acetate, and Zn-cysteine, indicating transformation and complexation within the plant. The findings demonstrate that a glutathione coating on GSH-ZnS-Mn QDs improves biocompatibility and nutrient delivery efficiency. These results highlight the relevance of surface functionalization in regulating nanoparticle fate, transformation, and nutrient bioavailability, supporting the potential application of GSH–ZnS–Mn QDs as modern nano fertilizers.

Basil↗
DOE OSTI2020

Single-phase Ru 1- x-y Mn x Co y O 2 nanoparticles as highly effective oxygen reduction electrocatalysts in alkaline media with enhanced stability and fuel-tolerance

Here, a series of single-phase binary and ternary ruthenium and transition metal oxide nanoparticles supported on Vulcan - Ru 1-x MnxO2/C, Ru1-xCoxO 2 /C, Ru 1-x-y MnxCo y O 2 /C, Ru 1-x Fe x O 2 /C, Ru 1-x Ni x O 2 /C and Ru 1-x V x O 2 /C, as well as RuO 2 /C, MnO 2 /C, Co 3 O 4 /C and Mn 3-x Co x O 4 /C - were synthesized via a facile method and studied for their oxygen reduction reaction (ORR) activity in alkaline media. Single-phase Ru 1-x Mn x O 2 /C, Ru 1-x-y Mn x Co y O 2 /C and Ru 1-x Co x O 2 /C catalysts significantly boosted ORR kinetics in alkaline media. Moreover, they were H 2 and methanol tolerant, and exhibited long term stability due to their single-phase structure. Ru 0.85 Mn 0.15 O 2 /C stood out as the most active catalyst among them. A volcano relationship of the ORR activity of these binary and ternary metal oxide catalysts vs. the O adsorption energy was found, with the maximum activity observed for the Ru 1-x Mn x O 2 /C, Ru 1-x-y Mn x Co y O 2 /C and Ru 1-x Co x O 2 /C catalysts due to their optimal O binding energy. These materials have potential applications as highly active ORR catalysts in alkaline fuel cells and metal-air batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Improving productivity and stability for CO 2 hydrogenation by using pincer-ligated Mn complexes with hemilabile ligands

Pincer ligands are widely used to support transition metal catalysts, but first-row systems often deactivate too quickly for widespread use. Here, pincer ligands bearing an additional hemilabile donor were designed to stabilize Mn catalysts for CO 2 hydrogenation to formate. Ligands of the type (RCH 2 CH 2 )N(CH 2 CH 2 P i Pr 2 ) 2 ( iPr PN R P; R = OMe, CH 2 OMe, NMe 2 , P i Pr 2 ) were synthesized and coordinated to Mn to form complexes of the type ( iPr PN R P)Mn(CO) 2 H. Their performance was compared to {MeN(CH 2 CH 2 P i Pr 2 ) 2 }Mn(CO) 2 H, which lacks a pendant donor. The pendant donor identity and arm length strongly influenced catalytic activity, but all pendant arm containing systems extended catalyst lifetime. Notably, ( iPr PN CH2OMe P)Mn(CO) 2 H achieved turnover frequencies of 158,000 h -1 and turnover numbers of 838,000, exceeding most state-of-the-art catalysts. Mechanistic studies revealed that hemilabile coordination enhances stability by avoiding deactivation, although excessive binding can lead to inactive states. Here, this work demonstrates hemilabile donors dramatically improve pincer-based Mn catalysts and provides design principles for broader applications.

CO2 hydrogenation↗
DOE OSTI2022

Water film-driven Mn (oxy)(hydr)oxide nanocoating growth on rhodochrosite

Minerals exposed to moist air stabilize thin water films that drive a score of chemical reactions of great importance to water-unsaturated terrestrial environments. In this study, we identified Mn (oxy)(hydr)oxide nanocoatings formed by the dissolution, oxidation and precipitation of Mn in oxygenated water films grown on rhodochrosite (MnCO 3 ) microparticles. Nanocoatings that could be identified by vibrational spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and (scanning and transmission) electron microscopy formed in water films containing the equivalent of at least 7 monolayers (~84 H 2 O/nm 2 ). These films were formed by exposing microparticles to moist air with at least 50% relative humidity (RH). Films of neutral pH reacted up to 14% of the Mn II located in the topmost ~5 nm region of the microparticles in atmospheres of up to 90% RH for 7 d. These reactions produced MnOOH, birnessite (MnO 2 ) and hausmannite (Mn 3 O 4 ) nanoparticles of low crystallinity, while exposure to atmospheric air for 1 yr. converted only 2% of Mn II in this region to MnOOH. In contrast, reactions in alkaline water films converted up to ~75% of the Mn II but only after 16 d of reaction. These films produced MnOOH and MnO 2 of low crystallinity, as well as crystalline hausmannite. Kinetic modeling of the time-resolved growth of the Mnsingle bondO stretching vibrational bands of these nanocoatings revealed two concurrent reaction processes. A 1 rst -order process was assigned to nucleation events terminating only after a few hours, and a 0-order process was assigned to the sustained growth of nanocoatings from these nuclei over longer reaction time. By identifying nanocoatings formed by water film-driven reactions on rhodochrosite, our study adds new insight into mineralogical transformations relevant to anoxic–oxic boundaries in water-unsaturated environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗