Phase Diagram and Transformations of Iron Pentacarbonyl to nm Layered Hematite and Carbon-Oxygen Polymer under Pressure

Ryu, Young Jay; Kim, Minseob; Yoo, Choong Shik

doi:10.1038/srep15139

Cited by 7 publications

(5 citation statements)

References 44 publications

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“…In literature, Raman spectrum of α-Fe 2 O 3 shows similar characteristic phonon modes, e.g., peak positions at 225 and 495 cm −1 are attributed to the A 1g mode, whereas, peak at positions 245, 290, 406, 611 and 818 cm −1 are attributed as E g modes [7,16,17,24]. The peak at 1309 cm −1 is also associated with the α-Fe 2 O 3 particle [7,25]. Moreover, the origin of the peak at 659 cm −1 is still not clear and discrepancies exist in literature.…”

Section: Raman Spectroscopic Studiesmentioning

confidence: 71%

Structural and optical properties of α-Fe₂O₃ nanoparticles realized by simple thermal decomposition route

Srivastava¹,

Kumar²

2020

Phys. Scr.

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Herein, we present the synthesis and thermal treatment effect of Hematite (α-Fe2O3). Hematite nanoparticles were prepared by repeated calcination of a precursor obtained from Fe(NO3)3.9H2O and Hexamethylenetetramine (HMTA). Thermal treatment of the precursor at 400 °C for 4 h, resulted in the formation of Fe3O4 nanoparticles, which on repeated calcination at 400 °C, 500 °C and 600 °C, resulted in α-Fe2O3 nanoparticles. Synthesized samples were characterized by using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and UV–vis spectroscopy techniques. XRD result reveals the formation of cubic Fe3O4 phase at 400 °C, which is transformed into rhombohedral α-Fe2O3 polymorphs on repeated calcination. Crystallinity of the α-Fe2O3 is enhanced on repeated calcination up to 500 °C after that it gets slightly amorphized at 600 °C. Raman and FTIR results further corroborate the XRD result. Optical band gap of most crystalline α-Fe2O3, as estimated from UV–vis results, is 1.87 eV. Urbach energy of the samples has been calculated from absorption data, which shows the minimum value for most crystalline material. These findings demonstrate the close relation between structure and optical properties of α-Fe2O3.

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Section: Raman Spectroscopic Studiesmentioning

confidence: 71%

Structural and optical properties of α-Fe₂O₃ nanoparticles realized by simple thermal decomposition route

Srivastava¹,

Kumar²

2020

Phys. Scr.

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“…Experiments performed at high pressures (GPa) on pure CO, produced a metastable CO polymer (Lipp et al, 2005 ) structurally characterized by partially interconnected polycarbonyl chains where the monomeric unit of five carbons contains a lactone moiety (Bernard et al, 1998 ). Further high pressure experiments conducted on Fe(CO) 5 resulted in a mixture of Fe 2 O 3 crystals immersed in a polymerized CO (Ryu et al, 2015 ). Overall, CO polymerization is a difficult reaction if a catalyst is not involved.…”

Section: Resultsmentioning

confidence: 99%

Complex Organic Matter Synthesis on Siloxyl Radicals in the Presence of CO

Fioroni

DeYonker

2021

Front. Chem.

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Heterogeneous phase astrochemistry plays an important role in the synthesis of complex organic matter (COM) as found on comets and rocky body surfaces like asteroids, planetoids, moons and planets. The proposed catalytic model is based on two assumptions: (a) siliceous rocks in both crystalline or amorphous states show surface-exposed defective centers such as siloxyl (Si-O•) radicals; (b) the second phase is represented by gas phase CO molecules, an abundant C1 building block found in space. By means of quantum chemistry; (DFT, PW6B95/def2-TZVPP); the surface of a siliceous rock in presence of CO is modeled by a simple POSS (polyhedral silsesquioxane) where a siloxyl (Si-O•) radical is present. Four CO molecules have been consecutively added to the Si-O• radical and to the nascent polymeric CO (pCO) chain. The first CO insertion shows no activation free energy with ΔG200K = −21.7 kcal/mol forming the SiO-CO• radical. The second and third CO insertions show ΔG200K‡ ≤ 10.5 kcal/mol. Ring closure of the SiO-CO-CO• (oxalic anhydride) moiety as well as of the SiO-CO-CO-CO• system (di-cheto form of oxetane) are thermodynamically disfavored. The last CO insertion shows no free energy of activation resulting in the stable five member pCO ring, precursor to 1,4-epoxy-1,2,3-butanone. Hydrogenation reactions of the pCO have been considered on the SiO oxygen or on the carbons and oxygens of the pCO chains. The formation of the reactive aldehyde SiO-CHO on the siliceous surface is possible. In principle, the complete hydrogenation of the (CO)1−4 series results in the formation of methanol and polyols. Furthermore, all the SiO-pCO intermediates and the lactone 1,4-epoxy-1,2,3-butanone product in its radical form can be important building blocks in further polymerization reactions and/or open ring reactions with H (aldehydes, polyols) or CN (chetonitriles), resulting in highly reactive multi-functional compounds contributing to COM synthesis.

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“…In this work, we have re-examined the structure and vibrational spectroscopy of Fe(CO) 5 , both of which have provided surprises. The diffraction study found a hitherto unknown phase transition, although a recent study of iron carbonyl using Raman spectroscopy had determined that two high-pressure phases exist in the region up to ∼16 GPa and ∼600 K, above which pressures and temperatures the material breaks down into a mixture of hematite and a polymeric C−O solid. In that work, the I → II phase boundary was represented by a straight line with a zero-pressure intercept at ∼160 K; however, the scatter of their observations is consistent with a steeper d T /d P at low pressure that could result in an intercept closer to 100 K. It thus seems reasonable to hypothesize that the high-pressure phase II is the same as our low-temperature phase II.…”

Section: Discussionmentioning

confidence: 99%

Structure and Spectroscopy of Iron Pentacarbonyl, Fe(CO)₅

Fortes

Parker

2022

J. Am. Chem. Soc.

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We have re-investigated the structure and vibrational spectroscopy of the iconic molecule iron pentacarbonyl, Fe(CO)5, in the solid state by neutron scattering methods. In addition to the known C2/c structure, we find that Fe(CO)5 undergoes a displacive ferroelastic phase transition at 105 K to a P1̅ structure. We propose that this is a result of certain intermolecular contacts becoming shorter than the sum of the van der Waals radii, resulting in an increased contribution of electrostatic repulsion to these interactions; this is manifested as a strain that breaks the symmetry of the crystal. Evaluation of the strain in a triclinic crystal required a description of the spontaneous strain in terms of a second-rank tensor, something that is feasible with high-precision powder diffraction data but practically very difficult using strain gauges on a single crystal of such low symmetry. The use of neutron vibrational spectroscopy (which is not subject to selection rules) has allowed the observation of all the fundamentals below 700 cm–1 for the first time. This has resulted in the re-assignment of several of the modes. Surprisingly, density functional theory calculations that were carried out to support the spectral assignments provided a poor description of the spectra.

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Phase Diagram and Transformations of Iron Pentacarbonyl to nm Layered Hematite and Carbon-Oxygen Polymer under Pressure

Cited by 7 publications

References 44 publications

Structural and optical properties of α-Fe₂O₃ nanoparticles realized by simple thermal decomposition route

Structural and optical properties of α-Fe₂O₃ nanoparticles realized by simple thermal decomposition route

Complex Organic Matter Synthesis on Siloxyl Radicals in the Presence of CO

Structure and Spectroscopy of Iron Pentacarbonyl, Fe(CO)₅

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Phase Diagram and Transformations of Iron Pentacarbonyl to nm Layered Hematite and Carbon-Oxygen Polymer under Pressure

Cited by 7 publications

References 44 publications

Structural and optical properties of α-Fe2O3 nanoparticles realized by simple thermal decomposition route

Structural and optical properties of α-Fe2O3 nanoparticles realized by simple thermal decomposition route

Complex Organic Matter Synthesis on Siloxyl Radicals in the Presence of CO

Structure and Spectroscopy of Iron Pentacarbonyl, Fe(CO)5

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Product

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Structural and optical properties of α-Fe₂O₃ nanoparticles realized by simple thermal decomposition route

Structural and optical properties of α-Fe₂O₃ nanoparticles realized by simple thermal decomposition route

Structure and Spectroscopy of Iron Pentacarbonyl, Fe(CO)₅