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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Molecular beam epitaxy and crystal structure of majority a -plane-oriented and substrate-strained Mn 3 Sn thin films grown directly on sapphire (0001)

The Kagome antiferromagnet Mn 3 Sn has garnered much attention due to the presence of exciting properties such as anomalous Hall and Nernst effects. This paper discusses the synthesis of crystalline Mn 3 Sn thin films, prepared on Al 2 O 3 (0001) substrates at 453 ± 5°C using molecular beam epitaxy. The growth is monitored in situ using reflection high energy electron diffraction and measured ex situ using x-ray diffraction, Rutherford back-scattering, and cross-sectional scanning transmission electron microscopy. Our analysis shows the in-plane lattice constants of a 1,M = 4.117 ± 0.027 Å and a 2,M = 4.943 ± 0.033 Å, which is a very unexpected result when compared to the bulk a-plane Mn 3 Sn. This indicates a strain in the film and makes it challenging to provide a straightforward explanation. In an effort to explain our results, we discuss two possible orientation relationships between the Mn 3 Sn films and the sapphire substrates. Samples prepared under these conditions appear to have smooth surfaces locally, but overall the film has a 3D island morphology. First-principles calculations provide atomic models of the Mn 3 Sn (112¯0) lattice on Al 2 O 3 (0001) high symmetry sites, indicating that the L3-R90° is the most stable configuration. A detailed discussion of the experimental data and theoretical results, as well as strain effects, is provided.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Long-Range Allosteric Communication Modulated by Active Site Mn(II) Coordination Drives Catalysis in Xanthobacter autotrophicus Acetone Carboxylase

Acetone carboxylase (AC) from Xanthobacter autotrophicus is a 360 KDa α2β2γ2 heterohexamer that catalyzes the ATP-dependent formation of phosphorylated acetone and bicarbonate intermediates that react at Mn(II) metal active sites to form acetoacetate. Structural models of X. autotrophicus AC (XaAC) with and without nucleotides reveal that the binding and phosphorylation of the two substrates occurs ~40 Å from the Mn(II) active sites where acetoacetate is formed. Based on the crystal structures, a significant conformational change was proposed to open and close a tunnel that facilitates the passage of reaction intermediates between the sites for nucleotide binding and phosphorylation of substrates and Mn(II) sites of acetoacetate formation. We have employed electron paramagnetic resonance (EPR), kinetic assays, and hydrogen/deuterium exchange mass spectrometry (HDX-MS) of poised ligand-bound states and site-specific amino acid variants to complete an in-depth analysis of Mn(II) coordination and allosteric communication throughout the catalytic cycle. In contrast with the established paradigms for carboxylation, our analyses of XaAC suggested a carboxylate shift that couples both local and long-range structural transitions. Shifts in the coordination mode of a single carboxylic acid residue (αE89) mediate both catalysis proximal to a Mn(II) center and communication with an ATP active site in a separate subunit of a 180 kDa α2β2γ2 complex at a distance of 40 Å. This work demonstrates the power of combining structural models from X-ray crystallography with solution-phase spectroscopy and biophysical techniques to elucidate functional aspects of a multi-subunit enzyme.

Biochemistry & Molecular Biology↗
NASA NTRS1984

Theory of high-harmonic rectangular gyrotron for TE(mn) modes

In this paper, the linearized relativistic Vlasov equation is solved and a dispersion relation is calculated for the interaction between a relativistic electron beam and the electromagnetic fields of a rectangular waveguide supporting TE(mn) modes. The dispersion relation is simplified to the special case of a frame of reference moving with the electrons and the resulting coupling coefficient epsilon(mn)super l is calculated for various TE(mn) modes. The dependence of epsilon(mn)super l on the parity of the harmonic number l and various mn modes of the waveguide are discussed.

Ferendeci, A. M.↗
NASA NTRS2002

Constraining the Material that Formed the Moon: The Origin of Lunar V, CR, and MN Depletions

The mantles of the Earth and Moon are similarly depleted in V, Cr, and Mn relative to chondritic values. Core formation deep within the Earth was suggested by as the origin of the depletions. Following Earth's core formation, the Moon was proposed to have inherited its mantle from the depleted mantle of the Earth by a giant impact event. This theory implied the Moon was primarily composed of material from the Earth's mantle. Recent systematic metal-silicate experiments of V, Cr, and Mn evaluated the behavior of these elements during different core formation scenarios. The study found that the V, Cr, and Mn depletions in the Earth could indeed be explained by core formation. The conditions of core formation necessary to deplete V, Cr, and Mn in the Earth's mantle were consistent with the deep magma ocean proposed to account for the Earth's mantle abundances of Ni and Co. Using the parameterizations of for the metal-silicate partition coefficients (D) of V, Cr, and Mn, we investigate here the conditions needed to match the depletions in the silicate Moon and determine if such conditions could have been present on the giant impactor.

Chabot, N. L.↗
DOE OSTI2020

Mn-doped oxide nuclear fuel

A nuclear fuel includes uranium(IV) oxide (UO2) and manganese (Mn) as a dopant. The Mn dopant may be present in the fuel in an amount up to the solubility limit for Mn under a given set of conditions, for example, about 0.01 wt % to about 1 wt %. The nuclear fuel is substantially free of aluminum (Al). The nuclear fuel exhibits enhanced grain size development during sintering temperatures as low at 1400 K due to an increase in uranium sub-lattice vacancies induced by dissolution of the Mn dopant at interstitial defect sites. The Mn-doped nuclear fuel exhibits improved grain sizes at lower temperatures compared to Cr-, Al-, and undoped UO2, and therefore desirably exhibits lower fission gas release and higher plasticity, reducing the chances of fuel rod failure.

Cooper, Michael William Donald↗
DOE OSTI2020

Materials Data on Mn(CoO2)2 by Materials Project

MnCo2O4 is Spinel-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share a cornercorner with one MnO4 tetrahedra, corners with five CoO4 tetrahedra, an edgeedge with one MnO6 octahedra, and edges with five CoO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.94–2.20 Å. In the second Mn2+ site, Mn2+ is bonded to four O2- atoms to form MnO4 tetrahedra that share corners with three MnO6 octahedra and corners with nine CoO6 octahedra. The corner-sharing octahedra tilt angles range from 56–64°. There are a spread of Mn–O bond distances ranging from 1.99–2.05 Å. In the third Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent MnO4 tetrahedra, corners with four CoO4 tetrahedra, an edgeedge with one MnO6 octahedra, and edges with five CoO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.92–2.18 Å. In the fourth Mn2+ site, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six CoO4 tetrahedra, edges with two MnO6 octahedra, and edges with four CoO6 octahedra. There are a spread of Mn–O bond distances ranging from 1.93–2.17 Å. There are eight inequivalent Co3+ sites. In the first Co3+ site, Co3+ is bonded to four O2- atoms to form CoO4 tetrahedra that share corners with six MnO6 octahedra and corners with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 53–65°. There are a spread of Co–O bond distances ranging from 1.94–2.00 Å. In the second Co3+ site, Co3+ is bonded to four O2- atoms to form CoO4 tetrahedra that share corners with three MnO6 octahedra and corners with nine CoO6 octahedra. The corner-sharing octahedra tilt angles range from 55–64°. There are a spread of Co–O bond distances ranging from 1.93–2.02 Å. In the third Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent MnO4 tetrahedra, corners with four CoO4 tetrahedra, edges with three MnO6 octahedra, and edges with three CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.90–1.97 Å. In the fourth Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one MnO4 tetrahedra, corners with five CoO4 tetrahedra, edges with three MnO6 octahedra, and edges with three CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.94–1.97 Å. In the fifth Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one MnO4 tetrahedra, corners with five CoO4 tetrahedra, edges with three MnO6 octahedra, and edges with three CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.92–1.97 Å. In the sixth Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent MnO4 tetrahedra, corners with four CoO4 tetrahedra, edges with three MnO6 octahedra, and edges with three CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.93–1.97 Å. In the seventh Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with three equivalent MnO4 tetrahedra, corners with three equivalent CoO4 tetrahedra, edges with two MnO6 octahedra, and edges with four CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.90–1.96 Å. In the eighth Co3+ site, Co3+ is bonded to four O2- atoms to form CoO4 tetrahedra that share corners with six MnO6 octahedra and corners with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 53–65°. There are a spread of Co–O bond distances ranging from 1.94–2.01 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mn2+ and three Co3+ atoms. In the second O2- site, O2- is bonded to one Mn2+ and three Co3+ atoms to form distorted corner-sharing OMnCo3 trigonal pyramids. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Co3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Co3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mn2+ and three Co3+ atoms. In the sixth O2- site, O2- is bonded to two Mn2+ and two Co3+ atoms to form distorted corner-sharing OMn2Co2 tetrahedra. In the seventh O2- site, O2- is bonded to one Mn2+ and three Co3+ atoms to form distorted OMnCo3 tetrahedra that share corners with two OMn2Co2 tetrahedra, a cornercorner with one OMnCo3 trigonal pyramid, and an edgeedge with one OMn2Co2 tetrahedra. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mn2+ and three Co3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mn2+ and three Co3+ atoms. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Co3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mn2+ and three Co3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mn2+ and three Co3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Co3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Co3+ atoms. In the fifteenth O2- site, O2- is bonded to two Mn2+ and two Co3+ atoms to form distorted OMn2Co2 tetrahedra that share corners with two OMn2Co2 tetrahedra, a cornercorner with one OMnCo3 trigonal pyramid, and an edgeedge with one OMnCo3 tetrahedra. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mn2+ and two Co3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(PO3)3 by Materials Project

Mn(PO3)3 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are three inequivalent Mn3+ sites. In the first Mn3+ site, Mn3+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 1.92–2.09 Å. In the second Mn3+ site, Mn3+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 1.94–2.15 Å. In the third Mn3+ site, Mn3+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 1.95–2.11 Å. There are nine inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 24–37°. There are a spread of P–O bond distances ranging from 1.48–1.61 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–42°. There are a spread of P–O bond distances ranging from 1.49–1.61 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–37°. There are a spread of P–O bond distances ranging from 1.48–1.60 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–38°. There are a spread of P–O bond distances ranging from 1.49–1.60 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–44°. There are a spread of P–O bond distances ranging from 1.50–1.59 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–37°. There are a spread of P–O bond distances ranging from 1.48–1.62 Å. In the seventh P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–36°. There are a spread of P–O bond distances ranging from 1.49–1.62 Å. In the eighth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–45°. There are a spread of P–O bond distances ranging from 1.48–1.63 Å. In the ninth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of P–O bond distances ranging from 1.50–1.60 Å. There are twenty-seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the twentieth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-first O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-second O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the twenty-fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the twenty-sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the twenty-seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(N3O8)2 by Materials Project

Mn(NO6)2N2(NO2)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of four ammonia molecules; four nitrous acid molecules; and one Mn(NO6)2 sheet oriented in the (1, 0, 0) direction. In the Mn(NO6)2 sheet, Mn2+ is bonded in a distorted octahedral geometry to six O2- atoms. There are a spread of Mn–O bond distances ranging from 1.69–2.10 Å. N5+ is bonded in a bent 120 degrees geometry to two O2- atoms. Both N–O bond lengths are 1.26 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one N5+ and one O2- atom. The O–O bond length is 2.39 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one N5+ and one O2- atom. The O–O bond length is 3.02 Å. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Mn2+ and two O2- atoms. There is one shorter (1.29 Å) and one longer (2.38 Å) O–O bond length. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Mn2+ and three O2- atoms. There are one shorter (2.51 Å) and one longer (2.62 Å) O–O bond lengths. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Mn2+ and one O2- atom. The O–O bond length is 3.04 Å. In the sixth O2- site, O2- is bonded in a 6-coordinate geometry to six O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(PO4)2 by Materials Project

Mn(PO4)2 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one Mn(PO4)2 sheet oriented in the (0, 1, 1) direction. there are two inequivalent Mn7+ sites. In the first Mn7+ site, Mn7+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Mn–O bond distances ranging from 1.76–2.12 Å. In the second Mn7+ site, Mn7+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Mn–O bond distances ranging from 1.75–2.11 Å. There are four inequivalent P+4.50+ sites. In the first P+4.50+ site, P+4.50+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.47–1.51 Å. In the second P+4.50+ site, P+4.50+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.47–1.51 Å. In the third P+4.50+ site, P+4.50+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.47–1.51 Å. In the fourth P+4.50+ site, P+4.50+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.47–1.51 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one P+4.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one P+4.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one P+4.50+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one P+4.50+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn7+ and one P+4.50+ atom. In the thirteenth O2- site, O2- is bonded in a single-bond geometry to one Mn7+ atom. In the fourteenth O2- site, O2- is bonded in a single-bond geometry to one Mn7+ atom. In the fifteenth O2- site, O2- is bonded in a single-bond geometry to one Mn7+ atom. In the sixteenth O2- site, O2- is bonded in a single-bond geometry to one Mn7+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn(HCl)2 by Materials Project

Mn(HCl)2 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two Mn(HCl)2 ribbons oriented in the (0, 0, 1) direction. Mn2+ is bonded to two equivalent H and four equivalent Cl1- atoms to form edge-sharing MnH2Cl4 octahedra. Both Mn–H bond lengths are 1.66 Å. There are two shorter (2.31 Å) and two longer (2.32 Å) Mn–Cl bond lengths. H is bonded in a single-bond geometry to one Mn2+ atom. Cl1- is bonded in an L-shaped geometry to two equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Degradation of Adsorbed Bisphenol A by Soluble Mn(III)

Bisphenol A (BPA), a high production volume chemical and potential endocrine disruptor, is found to be associated with sediments and soils due to its hydrophobicity (log K OW of 3.42). Here, we used superfine powdered activated carbon (SPAC) with a particle size of 1.38 ± 0.03 μm as a BPA sorbent and assessed degradation of BPA by oxidized manganese (Mn) species. SPAC strongly sorbed BPA, and desorption required organic solvents. No degradation of adsorbed BPA (278.7 ± 0.6 mg BPA g –1 SPAC) was observed with synthetic, solid α-MnO 2 with a particle size of 15.41 ± 1.35 μm; however, 89% mass reduction occurred following the addition of 0.5 mM soluble Mn(III). Small-angle neutron scattering data suggested that both adsorption and degradation of BPA occurred in SPAC pores. The findings demonstrate that Mn(III) mediates oxidative transformation of dissolved and adsorbed BPA, the latter observation challenging the paradigm that contaminant desorption and diffusion out of pore structures are required steps for degradation. Soluble Mn(III) is abundant near oxic-anoxic interfaces, and the observation that adsorbed BPA is susceptible to degradation has implications for predicting, and possibly managing, the fate and longevity of BPA in environmental systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Effect of Cationic (Na + ) and Anionic (F – ) Co-Doping on the Structural and Electrochemical Properties of LiNi 1/3 Mn 1/3 Co 1/3 O 2 Cathode Material for Lithium-Ion Batteries

Elemental doping for substituting lithium or oxygen sites has become a simple and effective technique to improve the electrochemical performance of layered cathode materials. Compared with single-element doping, this work presents an unprecedented contribution to the study of the effect of Na + /F – co-doping on the structure and electrochemical performance of LiNi 1/3 Mn 1/3 Co 1/3 O 2 . The co-doped Li 1-z Na z Ni 1/3 Mn 1/3 Co 1/3 O 2-z F z (z = 0.025) and pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 materials were synthesized via the sol–gel method using EDTA as a chelating agent. Structural analyses, carried out by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, revealed that the Na + and F – dopants were successfully incorporated into the Li and O sites, respectively. The co-doping resulted in larger Li-slab spacing, a lower degree of cation mixing, and the stabilization of the surface structure, which substantially enhanced the cycling stability and rate capability of the cathode material. The Na/F co-doped LiNi 1/3 Mn 1/3 Co 1/3 O 2 electrode delivered an initial specific capacity of 142 mAh g –1 at a 1C rate (178 mAh g –1 at 0.1C), and it maintained 50% of its initial capacity after 1000 charge–discharge cycles at a 1C rate.

25 ENERGY STORAGE↗
DOE OSTI2021

Diffusional and Partitionless Ferrite‐to‐Austenite Phase Transformations during Intercritical Annealing of Medium‐Mn Steels

Experimental research on intercritical annealing of a cold‐rolled Fe–7Mn steel with ultralow carbon concentration is presented, providing insight into the efficacy of generating Mn‐enriched austenite during relatively short (≈1000 s) heat treatments compared with batch annealing, as well as the phase transformation mechanisms that can occur during intercritical annealing. It is shown through both bulk characterization and electron microscopy in conjunction with energy‐dispersive X‐ray spectroscopy that Mn partitioning to austenite occurs via diffusional, partitioning growth of austenite during these shorter treatments and that the intercritical temperature influences the level of Mn enrichment in austenite. Evidence of massive (partitionless) and diffusional (partitioning) transformations of ferrite to austenite occurring simultaneously in a single sample are also shown along with a thermodynamic rationale for this occurrence, which is suggested to be related to residual Mn‐banding that develops during solidification.

Mueller, Josh J.↗
DOE OSTI2022

Predicting the oxidation states of Mn ions in the oxygen-evolving complex of photosystem II using supervised and unsupervised machine learning

Abstract Serial Femtosecond Crystallography at the X-ray Free Electron Laser (XFEL) sources enabled the imaging of the catalytic intermediates of the oxygen evolution reaction of Photosystem II (PSII). However, due to the incoherent transition of the S-states, the resolved structures are a convolution from different catalytic states. Here, we train Decision Tree Classifier and K-means clustering models on Mn compounds obtained from the Cambridge Crystallographic Database to predict the S-state of the X-ray, XFEL, and CryoEM structures by predicting the Mn’s oxidation states in the oxygen-evolving complex. The model agrees mostly with the XFEL structures in the dark S 1 state. However, significant discrepancies are observed for the excited XFEL states (S 2 , S 3, and S 0 ) and the dark states of the X-ray and CryoEM structures. Furthermore, there is a mismatch between the predicted S-states within the two monomers of the same dimer, mainly in the excited states. We validated our model against other metalloenzymes, the valence bond model and the Mn spin densities calculated using density functional theory for two of the mismatched predictions of PSII. The model suggests designing a more optimized sample delivery and illumiation systems are crucial to precisely resolve the geometry of the advanced S-states to overcome the noncoherent S-state transition. In addition, significant radiation damage is observed in X-ray and CryoEM structures, particularly at the dangler Mn center (Mn4). Our model represents a valuable tool for investigating the electronic structure of the catalytic metal cluster of PSII to understand the water splitting mechanism.

Plant Sciences↗
DOE OSTI2020

Aqueous passivation of multi-principal element alloy Ni 38 Fe 20 Cr 22 Mn 10 Co 10 : Unexpected high Cr enrichment within the passive film

The aqueous passivation of a non-equiatomic Ni 38 Fe 20 Cr 22 Mn 10 Co 10 - at.% (Ni 40 Fe 20 Cr 20 Mn 10 Co 10 - wt.%) multi-principal element alloy (MPEA) was investigated in 0.1 M NaCl at pH 4 and compared to a conventional binary Ni 76 Cr 24 – at.% (Ni 78 Cr 22 – wt.%) alloy. The electrochemical behavior and oxide film characteristics were explored utilizing in-situ electrochemical and ex-situ surface-sensitive techniques. The passive film composition, thickness, and elemental valence states, as well as, the fate of each element were studied by in-situ atomic emission spectro-electrochemistry, ex-situ X-ray photoelectron spectroscopy, and atom probe tomography. The Ni 38 Fe 20 Cr 22 Mn 10 Co 10 MPEA demonstrated slightly better corrosion resistance compared to the binary Ni 76 Cr 24 , alloy. Passive films on the MPEA contained primarily Cr, and small amounts of Ni, Fe, Co and Mn, while dissolution of Ni, Fe, Co was observed. Ni 0 was enriched at the oxide/metal interface while Cr was depleted. Enrichment of Cr in the passive film occurred to a greater extent in the MPEA than for the Ni-Cr binary alloy. As a result, enrichment factors were determined and the origins of enrichment are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Perovskite evolution on La modified Mn 1.5 Co 1.5 O 4 spinel through thermal ageing with enhanced oxidation activity: Is sintering always an issue?

Non-precious metal oxides have great potential in catalytic deep oxidation of emitted hydrocarbons to help address various environmental pollution concerns. However, sintering issue is a stumbling block in practical application upon long-term high-temperature operation or thermal shock experience. Herein, La was applied to modify Mn 1.5 Co 1.5 O 4 spinel to get a highly active oxidation catalyst with exceptional stability against high-temperature thermal ageing treatment. With thermal ageing at 750 °C for 100 h, the La modified Mn–Co composite reached 90 % conversion in toluene oxidation at 265 °C under the high WHSV of 120,000 mL g -1 h -1 , while this value increased to 312 °C over blank Mn–Co spinel. The addition of La not only inhibited the growth of spinel nanocrystals, but also brought about perovskite formation through sintering, generating perovskite-spinel interfaces, thus enhancing both activity and stability. Meanwhile, the La modified Mn–Co spinel exhibited superior performance in presence of water or sulfur dioxide after thermal ageing treatment. In conclusion, this work offers a versatile strategy to design anti-sintering and active oxidation nanocatalysts based on non-precious metal oxides for industrial applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Increasing the composition range of a novel τ 11 -Al 4 Fe 1.7 Si alloy with additions of Mn

Automotive applications need low-cost, lightweight, high-temperature alloys to increase vehicle efficiency. The Al–Fe–Si system provides an opportunity to develop such a material, as it consists of three low-cost elements that are all abundant in nature. Specifically, the τ 11 -Al 4 Fe 1.7 Si ternary intermetallic phase is a high-temperature, lightweight phase with high strength and good corrosion resistance. However, this phase exhibits a narrow compositional range of stability, resulting in undesirable microstructures forming during solidification and processing, limiting its use in potential applications. Density functional theory (DFT) calculations and a thermodynamically-driven experimental approach utilizing diffusion couples were employed to study the effect of Mn on the stability and composition range of τ 11 -Al 4 Fe 1.7 Si. The DFT calculations showed a decrease in the energy of the structure when alloying with Mn. Experimental results confirmed the predictions from the DFT calculations, indicating that alloying with Mn increases the compositional range, and thus the processability of this phase. New phase diagrams and equilibria are proposed by exploring and determining phase boundaries for the τ 11 -Al 4 Fe 1.7 Si phase with Mn.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Epitaxial columnar growth of strain-free antiferromagnetic Weyl semimetal Mn 3 Sn on wurtzite c -plane GaN/Al 2 O 3 (0001)

Weyl semimetal thin films with excellent crystalline quality are of great interest for antiferromagnetic spintronics. Mn 3 Sn is one Weyl semimetal with great properties and promise for exciting science and applications. It has proven very challenging, however, to grow Mn 3 Sn thin films with smooth surfaces, negligible strain, and excellent crystallinity. In this work, we discuss the successful preparation of epitaxial Mn 3 Sn (0001)-oriented thin films via molecular beam epitaxial growth on c -plane wurtzite GaN which was grown by MBE on Al 2 O 3 (0001). We present the reflection high energy electron diffraction analysis along with x-ray diffraction in order to demonstrate the crystalline quality of the film, and we give atomic models to explain the epitaxial orientation relationships between the crystal lattices of the substrate, GaN layer, and Mn 3 Sn layer. Importantly, we discuss the film lattice parameters as compared to expected values, demonstrating negligible strain both in-plane and out-of-plane . Atomic force microscopy reveals an epitaxial columnar growth mode characterized by flat-top-mesa islands, while scanning tunneling microscopy shows the atomically smooth surfaces of the mesa-top structures. Finally, Rutherford backscattering informs the stoichiometry of the film as well as the layer thicknesses.

Chiral antiferromagnetic material↗