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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CoMo3 by Materials Project

CoMo3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Mo sites. In the first Mo site, Mo is bonded in a distorted body-centered cubic geometry to four equivalent Mo and four equivalent Co atoms. All Mo–Mo bond lengths are 2.66 Å. All Mo–Co bond lengths are 2.66 Å. In the second Mo site, Mo is bonded in a 8-coordinate geometry to eight equivalent Mo and six equivalent Co atoms. All Mo–Co bond lengths are 3.08 Å. Co is bonded in a distorted body-centered cubic geometry to fourteen Mo atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na4Co9(MoO4)12 by Materials Project

Na4Co9(MoO4)12 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share a cornercorner with one CoO6 octahedra, corners with six MoO4 tetrahedra, and edges with two equivalent NaO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 67°. There are a spread of Na–O bond distances ranging from 2.29–2.51 Å. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share a cornercorner with one CoO6 octahedra, corners with six MoO4 tetrahedra, and edges with two equivalent NaO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 69°. There are a spread of Na–O bond distances ranging from 2.28–2.51 Å. In the third Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with two CoO6 octahedra, corners with six MoO4 tetrahedra, and edges with two equivalent NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 63–68°. There are a spread of Na–O bond distances ranging from 2.36–2.41 Å. In the fourth Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with two CoO6 octahedra, corners with six MoO4 tetrahedra, and edges with two equivalent NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 62–68°. There are a spread of Na–O bond distances ranging from 2.35–2.43 Å. There are twelve inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 28–53°. There are a spread of Mo–O bond distances ranging from 1.74–1.86 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 28–53°. There are a spread of Mo–O bond distances ranging from 1.74–1.86 Å. In the third Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 19–63°. There are a spread of Mo–O bond distances ranging from 1.76–1.87 Å. In the fourth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 45–63°. There are a spread of Mo–O bond distances ranging from 1.76–1.85 Å. In the fifth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 18–56°. There are a spread of Mo–O bond distances ranging from 1.76–1.89 Å. In the sixth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 37–55°. There are a spread of Mo–O bond distances ranging from 1.75–1.91 Å. In the seventh Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with five CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 28–60°. There are a spread of Mo–O bond distances ranging from 1.75–1.83 Å. In the eighth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with five CoO6 octahedra and corners with three NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 29–59°. There are a spread of Mo–O bond distances ranging from 1.75–1.83 Å. In the ninth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with five CoO6 octahedra. The corner-sharing octahedra tilt angles range from 40–63°. There are a spread of Mo–O bond distances ranging from 1.77–1.85 Å. In the tenth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with five CoO6 octahedra. The corner-sharing octahedra tilt angles range from 14–62°. There are a spread of Mo–O bond distances ranging from 1.77–1.85 Å. In the eleventh Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with seven CoO6 octahedra. The corner-sharing octahedra tilt angles range from 25–65°. There are a spread of Mo–O bond distances ranging from 1.76–1.84 Å. In the twelfth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with seven CoO6 octahedra. The corner-sharing octahedra tilt angles range from 26–64°. There are a spread of Mo–O bond distances ranging from 1.76–1.84 Å. There are nine inequivalent Co+2.22+ sites. In the first Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six MoO4 tetrahedra. There are a spread of Co–O bond distances ranging from 2.06–2.15 Å. In the second Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six MoO4 tetrahedra and faces with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 2.03–2.18 Å. In the third Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six MoO4 tetrahedra and faces with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 2.03–2.19 Å. In the fourth Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, corners with six MoO4 tetrahedra, and edges with two equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 54°. There are a spread of Co–O bond distances ranging from 1.99–2.24 Å. In the fifth Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, corners with six MoO4 tetrahedra, and edges with two equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are a spread of Co–O bond distances ranging from 1.99–2.26 Å. In the sixth Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, and corners with six MoO4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. There are a spread of Co–O bond distances ranging from 1.87–2.39 Å. In the seventh Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, and corners with six MoO4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. There are a spread of Co–O bond distances ranging from 1.86–2.37 Å. In the eighth Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one NaO6 pentagonal pyramid, corners with six MoO4 tetrahedra, and edges with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 2.00–2.19 Å. In the ninth Co+2.22+ site, Co+2.22+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one NaO6 pentagonal pyramid, corners with six MoO4 tetrahedra, and edges with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 2.02–2.29 Å. There are forty-eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mo6+ and two Co+2.22+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the sixteenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the seventeenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one Mo6+ atom. In the eighteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one Mo6+ atom. In the nineteenth O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+2.22+ atom. In the twentieth O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+2.22+ atom. In the twenty-first O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+2.22+ atom. In the twenty-second O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+2.22+ atom. In the twenty-third O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+2.22+ atom. In the twenty-fourth O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+2.22+ atom. In the twenty-fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the twenty-sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the twenty-seventh O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the twenty-eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the twenty-ninth O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the thirtieth O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the thirty-first O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the thirty-second O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and one Mo6+ atom. In the thirty-third O2- site, O2- is bonded in a bent 120 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the thirty-fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Mo6+ and one Co+2.22+ atom. In the thirty-fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the thirty-sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two Co+2.22+ atoms. In the thirty-seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mo6+ and one Co+2.22+ a

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mo3C2 by Materials Project

Mo3C2 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one Mo2C sheet oriented in the (0, 0, 1) direction and one Mo4C3 sheet oriented in the (0, 0, 1) direction. In the Mo2C sheet, Mo+2.67+ is bonded in a distorted T-shaped geometry to three equivalent C4- atoms. All Mo–C bond lengths are 2.14 Å. C4- is bonded to six equivalent Mo+2.67+ atoms to form edge-sharing CMo6 octahedra. In the Mo4C3 sheet, there are two inequivalent Mo+2.67+ sites. In the first Mo+2.67+ site, Mo+2.67+ is bonded in a distorted T-shaped geometry to three equivalent C4- atoms. All Mo–C bond lengths are 2.07 Å. In the second Mo+2.67+ site, Mo+2.67+ is bonded to six C4- atoms to form a mixture of edge and corner-sharing MoC6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (2.18 Å) and three longer (2.23 Å) Mo–C bond lengths. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded to six equivalent Mo+2.67+ atoms to form a mixture of edge and corner-sharing CMo6 octahedra. The corner-sharing octahedral tilt angles are 2°. In the second C4- site, C4- is bonded to six Mo+2.67+ atoms to form a mixture of edge and corner-sharing CMo6 octahedra. The corner-sharing octahedral tilt angles are 2°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Determination of the N–H Bond Dissociation Free Energy in a Pyridine(diimine)molybdenum Complex Prepared by Proton-Coupled Electron Transfer

The pyridine(diimine) molybdenum bis(imido) complex, ( iPr PDI)Mo(=NTol) 2 (Tol = 4-methylphenyl) was synthesized by addition of two equivalents of 4-methylphenylazide to a corresponding molybdenum benzene derivative, ( iPr PDI)Mo(η 6 -C 6 H 6 ) ( iPr PDI = 2,6-(2,6-iPr 2 C 6 H 3 N=CMe) 2 C 5 H 3 N). Protonation of ( iPr PDI)Mo(=NTol) 2 with 2,6-lutinidum triflate yielded a cationic molybdenum amido complex, [( iPr PDI)Mo(NHTol)(=NTol)][OTf], which was further transformed into the neutral molybdenum amido complex, ( iPr PDI)Mo(NHTol)(=NTol) by reduction with zinc powder. A series of spectroscopic, synthetic and pK a determination studies along with electrochemical measurements by the protonation-reduction pathway were used to establish an N–H bond dissociation free energy (BDFE) between 65-69 kcal/mol for the molybdenum imido-amido compound, ( iPr PDI)Mo(NHTol)(=NTol). Full molecule DFT studies provided a computed value of 61 kcal/mol. By contrast, reduction of ( iPr PDI)Mo(=NTol) 2 with KC 8 afforded the corresponding anionic molybdenum complex, K[( iPr PDI)Mo(=NTol) 2 ] that has a potassium cation intercalated with the pyridine and the tolyl groups. Protonation of K[( iPr PDI)Mo(=NTol) 2 ] with the weak amidinium acids [TBD(H)][BArF 24 ] (TBD = triazabicyclodecene, BArF 24 = B[3,5-(CF 3 ) 2 C 6 H 3 ] 4 ) also produced the neutral molybdenum amido complex, ( iPr PDI)Mo(NHTol)(=NTol). Measurement of the pKa and oxidation potential of K[( iPr PDI)Mo(=NTol) 2 ] provided a range of 69-73 kcal/mol for the N–H BDFE of ( iPr PDI)Mo(NHTol)(=NTol), in good agreement with the protonation-reduction route and completing the square scheme. The similar pK a and redox potentials obtained from each pathway demonstrate that both sequences are energetically feasible for PCET events. This study on the determination of N–H BDFE of the molybdenum amido complex renders fundamental insight into the N 2 reduction cycle by proton-coupled electron transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis and Structure–Activity Characterization of a Single-Site MoO 2 Catalytic Center Anchored on Reduced Graphene Oxide

Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances have been made with well-defined oxide supports, the structural complexity of other supports and the nature of the grafted surface species present an intriguing challenge. In this study, single-site Mo(=O) 2 species grafted onto reduced graphene oxide (rGO/MoO 2 ) are characterized by XPS, DRIFTS, powder XRD, N 2 physisorption, NH 3 -TPD, aqueous contact angle, active site poisoning assay, Mo EXAFS, model compound single-crystal XRD, DFT, and catalytic performance. NH 3 -TPD reveals that the anchored MoO 2 moiety is not strongly acidic, while Mo 3d 5/2 XPS assigns the oxidation state as Mo(VI), and XRD shows little rGO periodicity change on MoO 2 grafting. Contact angle analysis shows that MoO 2 grafting consumes rGO surface polar groups, yielding a more hydrophobic surface. The rGO/MoO 2 DRIFTS assigns features at 959 and 927 cm –1 to the symmetric and antisymmetric Mo=O stretching modes, respectively, of an isolated cis-(O=Mo=O) moiety, in agreement with DFT computation. Moreover, the Mo EXAFS rGO/MoO 2 structural data are consistent with isolated (C–O) 2– Mo(=O) 2 species having two Mo=O bonds and two Mo–O bonds at distances of 1.69(3) and 1.90(3) Å, respectively. rGO/MoO 2 is also more active than the previously reported AC/MoO 2 catalyst, with reductive carbonyl coupling TOFs approaching 1.81 × 10 3 h –1 . rGO/MoO 2 is environmentally robust and multiply recyclable with 69 ± 2% of the Mo sites catalytically significant. Altogether, rGO/MoO 2 is a structurally well-defined and versatile single-site Mo(VI) dioxo heterogeneous catalytic system.

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

The 2022 magneto-optics roadmap

Abstract Magneto-optical (MO) effects, viz. magnetically induced changes in light intensity or polarization upon reflection from or transmission through a magnetic sample, were discovered over a century and a half ago. Initially they played a crucially relevant role in unveiling the fundamentals of electromagnetism and quantum mechanics. A more broad-based relevance and wide-spread use of MO methods, however, remained quite limited until the 1960s due to a lack of suitable, reliable and easy-to-operate light sources. The advent of Laser technology and the availability of other novel light sources led to an enormous expansion of MO measurement techniques and applications that continues to this day (see section 1). The here-assembled roadmap article is intended to provide a meaningful survey over many of the most relevant recent developments, advances, and emerging research directions in a rather condensed form, so that readers can easily access a significant overview about this very dynamic research field. While light source technology and other experimental developments were crucial in the establishment of today’s magneto-optics, progress also relies on an ever-increasing theoretical understanding of MO effects from a quantum mechanical perspective (see section 2), as well as using electromagnetic theory and modelling approaches (see section 3) to enable quantitatively reliable predictions for ever more complex materials, metamaterials, and device geometries. The latest advances in established MO methodologies and especially the utilization of the MO Kerr effect (MOKE) are presented in sections 4 (MOKE spectroscopy), 5 (higher order MOKE effects), 6 (MOKE microscopy), 8 (high sensitivity MOKE), 9 (generalized MO ellipsometry), and 20 (Cotton–Mouton effect in two-dimensional materials). In addition, MO effects are now being investigated and utilized in spectral ranges, to which they originally seemed completely foreign, as those of synchrotron radiation x-rays (see section 14 on three-dimensional magnetic characterization and section 16 on light beams carrying orbital angular momentum) and, very recently, the terahertz (THz) regime (see section 18 on THz MOKE and section 19 on THz ellipsometry for electron paramagnetic resonance detection). Magneto-optics also demonstrates its strength in a unique way when combined with femtosecond laser pulses (see section 10 on ultrafast MOKE and section 15 on magneto-optics using x-ray free electron lasers), facilitating the very active field of time-resolved MO spectroscopy that enables investigations of phenomena like spin relaxation of non-equilibrium photoexcited carriers, transient modifications of ferromagnetic order, and photo-induced dynamic phase transitions, to name a few. Recent progress in nanoscience and nanotechnology, which is intimately linked to the achieved impressive ability to reliably fabricate materials and functional structures at the nanoscale, now enables the exploitation of strongly enhanced MO effects induced by light–matter interaction at the nanoscale (see section 12 on magnetoplasmonics and section 13 on MO metasurfaces). MO effects are also at the very heart of powerful magnetic characterization techniques like Brillouin light scattering and time-resolved pump-probe measurements for the study of spin waves (see section 7), their interactions with acoustic waves (see section 11), and ultra-sensitive magnetic field sensing applications based on nitrogen-vacancy centres in diamond (see section 17). Despite our best attempt to represent the field of magneto-optics accurately and do justice to all its novel developments and its diversity, the research area is so extensive and active that there remains great latitude in deciding what to include in an article of this sort, which in turn means that some areas might not be adequately represented here. However, we feel that the 20 sections that form this 2022 magneto-optics roadmap article, each written by experts in the field and addressing a specific subject on only two pages, provide an accurate snapshot of where this research field stands today. Correspondingly, it should act as a valuable reference point and guideline for emerging research directions in modern magneto-optics, as well as illustrate the directions this research field might take in the foreseeable future.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

ModE Regulates Alternative Nitrogenase Expression in the Methanogen Methanosarcina acetivorans

ABSTRACT All methanogens that can fix nitrogen use molybdenum (Mo) nitrogenase. Some methanogens, including Methanosarcina acetivorans , also contain alternative vanadium‐ and iron‐nitrogenases, encoded by the vnf and anf operons, respectively. These nitrogenases are produced when there is insufficient Mo to support Mo‐nitrogenase activity. The factors that control the expression of the alternative nitrogenases in response to Mo availability are unknown in methanogens. Here we show that ModE is the regulator that represses transcription of the vnf and anf operons in M. acetivorans when cells are grown with Mo. CRISPRi repression of modE results in a significant increase in the transcription of the vnf and anf operons as well as the detection of Fe‐nitrogenase during nitrogen fixation in the presence of Mo. Gel shift assays with recombinant ModE demonstrated that ModE binds a specific sequence motif upstream of the vnf and anf operons, as well as other genes and operons related to nitrogen fixation and Mo transport. However, purified ModE does not contain Mo, and the addition of Mo does not alter the affinity of ModE for DNA, indicating M. acetivorans ModE may not directly bind Mo. This study shows that ModE is the primary Mo‐responsive regulator of alternative nitrogenase expression in M. acetivorans , but other factor(s) are likely involved in directly sensing Mo.

Chanderban, Melissa [Department of Biological Scie↗
DOE OSTI2024

High Temperature Tensile Testing of Molybdenum Before and After Exposure in Flowing He at 600°C to 1000°C

ORNL supported NorthStar Medical Radioisotope’s accelerator-based concept to produce the medical isotope molybdenum-99 (Mo-99). The Mo targets are expected to experience in the accelerator temperature ranging from 200°C to 1000°C, and previous studies have demonstrated the embrittlement of Mo targets at room temperature when exposed to impure He at 800 to 1000°C. The goal of this project was to evaluate potential embrittlement at temperature ranging from 600°C to 1000°C for three Mo materials exposed at the same temperatures for 100h in high purity He (O 2 < 5ppm (µl/l)) with a flow rate of ~1m/s. Enriched Mo-100 (aMo) and conventional pressed and sintered Mo (UHP) disks were provided by NorthStar while low carbon arc cast rolled Mo, fabricated at ORNL, was used for comparison. The as fabricated rolled Mo exhibited superior tensile strength due to the alloy very fine grain size with limited ductility except at 1000°C with the elongation at rupture reaching 30%. The UHP Mo disks showed the lowest strength but highest ductility at 20-1000°C with significant strain hardening during tensile testing. The ductility of the aMo material was quite low at all temperatures due to a high density of voids at grain boundaries. Significant embrittlement of the aMo material was observed after exposure at 600°C to 1000°C, most likely because of oxygen diffusion and segregation at grain boundaries. No embrittlement was observed for the UHP Mo material, with excellent elongation at rupture for some of the specimens oxidized in He and tested at 600-1000°C. Significant variation in ductility from one UHP Mo specimen to another was, however, measured, both in the as fabricated and He-oxidized conditions. The rolled Mo was not affected by oxidation in He at 800°C, but a decrease in strength and increase in ductility was observed at 1000°C, likely due to the material recrystallization.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al8Mo3 by Materials Project

Al8Mo3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Mo sites. In the first Mo site, Mo is bonded to twelve Al atoms to form a mixture of distorted face and edge-sharing MoAl12 cuboctahedra. There are a spread of Mo–Al bond distances ranging from 2.64–3.00 Å. In the second Mo site, Mo is bonded in a 11-coordinate geometry to eleven Al atoms. There are a spread of Mo–Al bond distances ranging from 2.56–2.98 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to four Mo and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.66–2.94 Å. In the second Al site, Al is bonded in a distorted rectangular see-saw-like geometry to four Mo and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.81–2.96 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to four Mo and eight Al atoms. There are two shorter (2.69 Å) and one longer (2.87 Å) Al–Al bond lengths. In the fourth Al site, Al is bonded in a 12-coordinate geometry to five equivalent Mo and seven Al atoms. There are one shorter (2.72 Å) and two longer (2.85 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ga(MoS2)4 by Materials Project

GaMo4S8 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Mo+3.25+ sites. In the first Mo+3.25+ site, Mo+3.25+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share corners with three equivalent GaS4 tetrahedra, edges with four equivalent MoS6 octahedra, and edges with two equivalent MoS6 pentagonal pyramids. There are a spread of Mo–S bond distances ranging from 2.35–2.62 Å. In the second Mo+3.25+ site, Mo+3.25+ is bonded to six S2- atoms to form distorted MoS6 pentagonal pyramids that share corners with three equivalent GaS4 tetrahedra and edges with six equivalent MoS6 octahedra. There are three shorter (2.37 Å) and three longer (2.64 Å) Mo–S bond lengths. Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with nine equivalent MoS6 octahedra and corners with three equivalent MoS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 65°. There are one shorter (2.31 Å) and three longer (2.32 Å) Ga–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to three Mo+3.25+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SGaMo3 tetrahedra. In the second S2- site, S2- is bonded to three equivalent Mo+3.25+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SGaMo3 tetrahedra. In the third S2- site, S2- is bonded in a 3-coordinate geometry to three Mo+3.25+ atoms. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent Mo+3.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Al2Mo)2 by Materials Project

YbMo2Al4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 4-coordinate geometry to twelve Al atoms. There are four shorter (2.91 Å) and eight longer (3.26 Å) Yb–Al bond lengths. Mo is bonded in a 10-coordinate geometry to two equivalent Mo and eight Al atoms. Both Mo–Mo bond lengths are 2.67 Å. All Mo–Al bond lengths are 2.79 Å. There are six inequivalent Al sites. In the first Al site, Al is bonded in a 11-coordinate geometry to three equivalent Yb, four equivalent Mo, and four Al atoms. There are two shorter (2.65 Å) and two longer (2.87 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 11-coordinate geometry to three equivalent Yb, four equivalent Mo, and four Al atoms. There are one shorter (2.65 Å) and two longer (2.87 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 11-coordinate geometry to three equivalent Yb, four equivalent Mo, and four Al atoms. There are one shorter (2.65 Å) and two longer (2.87 Å) Al–Al bond lengths. In the fourth Al site, Al is bonded in a 11-coordinate geometry to three equivalent Yb, four equivalent Mo, and four Al atoms. There are two shorter (2.65 Å) and two longer (2.87 Å) Al–Al bond lengths. In the fifth Al site, Al is bonded in a 11-coordinate geometry to three equivalent Yb, four equivalent Mo, and four Al atoms. The Al–Al bond length is 2.65 Å. In the sixth Al site, Al is bonded in a 11-coordinate geometry to three equivalent Yb, four equivalent Mo, and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BMo2C by Materials Project

Mo2BC crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Mo+3.50+ sites. In the first Mo+3.50+ site, Mo+3.50+ is bonded to one B3- and five equivalent C4- atoms to form a mixture of distorted edge and corner-sharing MoBC5 square pyramids. The Mo–B bond length is 2.76 Å. There are one shorter (2.16 Å) and four longer (2.19 Å) Mo–C bond lengths. In the second Mo+3.50+ site, Mo+3.50+ is bonded in a 1-coordinate geometry to six equivalent B3- and one C4- atom. There are four shorter (2.32 Å) and two longer (2.34 Å) Mo–B bond lengths. The Mo–C bond length is 2.09 Å. B3- is bonded in a 9-coordinate geometry to seven Mo+3.50+ and two equivalent B3- atoms. Both B–B bond lengths are 1.82 Å. C4- is bonded to six Mo+3.50+ atoms to form a mixture of edge and corner-sharing CMo6 octahedra. The corner-sharing octahedral tilt angles are 5°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U2Ge4Mo3 by Materials Project

U2Mo3Ge4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. U is bonded in a 7-coordinate geometry to two equivalent Mo and seven Ge atoms. There are one shorter (3.14 Å) and one longer (3.27 Å) U–Mo bond lengths. There are a spread of U–Ge bond distances ranging from 2.86–3.01 Å. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded to six Ge atoms to form distorted corner-sharing MoGe6 octahedra. The corner-sharing octahedral tilt angles are 47°. All Mo–Ge bond lengths are 2.69 Å. In the second Mo site, Mo is bonded in a 6-coordinate geometry to two equivalent U and six Ge atoms. There are a spread of Mo–Ge bond distances ranging from 2.55–2.69 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent U, four Mo, and one Ge atom. The Ge–Ge bond length is 2.76 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent U, five Mo, and one Ge atom. The Ge–Ge bond length is 2.78 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al(MoS2)4 by Materials Project

Al(MoS2)4 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Mo+3.25+ sites. In the first Mo+3.25+ site, Mo+3.25+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share corners with three equivalent AlS4 tetrahedra, edges with four equivalent MoS6 octahedra, and edges with two equivalent MoS6 pentagonal pyramids. There are a spread of Mo–S bond distances ranging from 2.34–2.63 Å. In the second Mo+3.25+ site, Mo+3.25+ is bonded to six S2- atoms to form distorted MoS6 pentagonal pyramids that share corners with three equivalent AlS4 tetrahedra and edges with six equivalent MoS6 octahedra. There are three shorter (2.37 Å) and three longer (2.64 Å) Mo–S bond lengths. Al3+ is bonded to four S2- atoms to form AlS4 tetrahedra that share corners with nine equivalent MoS6 octahedra and corners with three equivalent MoS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 65°. All Al–S bond lengths are 2.29 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent Mo+3.25+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three Mo+3.25+ atoms. In the third S2- site, S2- is bonded to three Mo+3.25+ and one Al3+ atom to form a mixture of distorted edge and corner-sharing SAlMo3 tetrahedra. In the fourth S2- site, S2- is bonded to three equivalent Mo+3.25+ and one Al3+ atom to form a mixture of distorted edge and corner-sharing SAlMo3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ga(MoS2)4 by Materials Project

GaMo4S8 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Mo+3.25+ sites. In the first Mo+3.25+ site, Mo+3.25+ is bonded to six S2- atoms to form distorted MoS6 octahedra that share corners with three equivalent GaS4 tetrahedra, edges with four equivalent MoS6 octahedra, and edges with two equivalent MoS6 pentagonal pyramids. There are a spread of Mo–S bond distances ranging from 2.35–2.62 Å. In the second Mo+3.25+ site, Mo+3.25+ is bonded to six S2- atoms to form distorted MoS6 pentagonal pyramids that share corners with three equivalent GaS4 tetrahedra and edges with six equivalent MoS6 octahedra. There are three shorter (2.37 Å) and three longer (2.63 Å) Mo–S bond lengths. Ga3+ is bonded to four S2- atoms to form GaS4 tetrahedra that share corners with nine equivalent MoS6 octahedra and corners with three equivalent MoS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 65°. All Ga–S bond lengths are 2.31 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent Mo+3.25+ atoms. In the second S2- site, S2- is bonded to three Mo+3.25+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SGaMo3 tetrahedra. In the third S2- site, S2- is bonded to three equivalent Mo+3.25+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SGaMo3 tetrahedra. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to three Mo+3.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(MoO2)6 by Materials Project

Pr(MoO2)6 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Pr3+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Pr–O bond lengths are 2.45 Å. There are two inequivalent Mo+3.50+ sites. In the first Mo+3.50+ site, Mo+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MoO6 octahedra. The corner-sharing octahedra tilt angles range from 49–57°. There are a spread of Mo–O bond distances ranging from 2.06–2.23 Å. In the second Mo+3.50+ site, Mo+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MoO6 octahedra. The corner-sharing octahedra tilt angles range from 49–52°. There are a spread of Mo–O bond distances ranging from 1.95–2.23 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Pr3+ and three Mo+3.50+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Mo+3.50+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to three Mo+3.50+ atoms. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to three Mo+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ga(MoSe2)4 by Materials Project

Ga(MoSe2)4 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Mo+3.25+ sites. In the first Mo+3.25+ site, Mo+3.25+ is bonded to six Se2- atoms to form distorted MoSe6 pentagonal pyramids that share corners with three equivalent GaSe4 tetrahedra and edges with six MoSe6 pentagonal pyramids. There are a spread of Mo–Se bond distances ranging from 2.47–2.76 Å. In the second Mo+3.25+ site, Mo+3.25+ is bonded to six Se2- atoms to form distorted MoSe6 pentagonal pyramids that share corners with three equivalent GaSe4 tetrahedra and edges with six equivalent MoSe6 pentagonal pyramids. There are three shorter (2.49 Å) and three longer (2.79 Å) Mo–Se bond lengths. Ga3+ is bonded to four Se2- atoms to form GaSe4 tetrahedra that share corners with twelve MoSe6 pentagonal pyramids. All Ga–Se bond lengths are 2.45 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Mo+3.25+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SeGaMo3 tetrahedra. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three Mo+3.25+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Mo+3.25+ atoms. In the fourth Se2- site, Se2- is bonded to three equivalent Mo+3.25+ and one Ga3+ atom to form a mixture of distorted edge and corner-sharing SeGaMo3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(MoO2)4 by Materials Project

K(MoO2)4 crystallizes in the tetragonal P4/n space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (3.01 Å) and four longer (3.16 Å) K–O bond lengths. In the second K1+ site, K1+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (3.08 Å) and four longer (3.12 Å) K–O bond lengths. There are two inequivalent Mo+3.75+ sites. In the first Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MoO6 octahedra. The corner-sharing octahedra tilt angles range from 48–55°. There are a spread of Mo–O bond distances ranging from 2.07–2.15 Å. In the second Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MoO6 octahedra. The corner-sharing octahedra tilt angles range from 48–53°. There are a spread of Mo–O bond distances ranging from 2.00–2.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two K1+ and three Mo+3.75+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Mo+3.75+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Mo+3.75+ atoms. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two K1+ and three Mo+3.75+ atoms.

36 MATERIALS SCIENCE↗