Dataset Information

Elusive Co2O3: A Combined Experimental and Theoretical Study.

ABSTRACT: Despite several oxides with trivalent cobalt ions are known, the sesquioxide M2O3 with Co3+ ions remains elusive. Our attempts to prepare Co2O3 have failed. However, 50% of Co3+ ions could be substituted for Ln3+ ions in Ln2O3 (Ln = Y and Lu) with a cubic bixbyite structure where the Co3+ ions are in the intermediate-spin state. We have therefore examined the structural stability of Co2O3 and the special features of solid solutions (Ln0.5Co0.5)2O3 (Ln = Y and Lu). The experimental results are interpreted in the context of ab initio-based density functional theory, molecular dynamics (AIMD), and crystal orbital Hamiltonian population (COHP) analysis. Our AIMD study signifies that Co2O3 in a corundum structure is not stable. COHP analysis shows that there is instability in Co2O3 structures, whereas Co and O have a predominantly bonding character in the bixbyite structure of the solid solution (Y0.5Co0.5)2O3.

SUBMITTER: Shanbhag PN

PROVIDER: S-EPMC7675568 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Elusive Co2O3: A Combined Experimental and Theoretical Study.

Shanbhag Pavitra N PN Biswas Raju K RK Pati Swapan K SK Sundaresan Athinarayanan A Rao Chinthamani Nagesa Ramachandra CNR

ACS omega 20201102 45

Despite several oxides with trivalent cobalt ions are known, the sesquioxide M2O3 with Co3+ ions remains elusive. Our attempts to prepare Co2O3 have failed. However, 50% of Co3+ ions could be substituted for Ln3+ ions in Ln2O3 (Ln = Y and Lu) with a cubic bixbyite structure where the Co3+ ions are in the intermediate-spin state. We have therefore examined the structural stability of Co<s ...[more]

PMID: 33225132

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Project description:The gas-phase reaction between the ethyl cation (C2H5+) and ethyne (C2H2) is re-investigated by measuring absolute reactive cross sections (CSs) and branching ratios (BRs) as a function of collision energy, in the thermal and hyperthermal energy range, via tandem-guided ion beam mass spectrometry under single collision conditions. Dissociative photoionization of C2H5Br using tuneable VUV radiation in the range 10.5-14.0 eV is employed to generate C2H5+, which has also allowed us to explore the impact of increasing (vibrational) excitation on the reactivity. Reactivity experiments are complemented by theoretical calculations, at the G4 level of theory, of the relative energies and structures of the most relevant stationary points on the reactive potential energy hypersurface (PES) and by mass-analyzed ion kinetic energy (MIKE) spectrometry experiments to probe the metastable decomposition from the [C4H7]+ PES and elucidate the underlying reaction mechanisms. Two main product channels have been identified at a centre-of-mass collision energy of ∼0.1 eV: (a) C3H3++CH4, with BR = 0.76±0.05 and (b) C4H5++H2, with BR = 0.22±0.02. A third channel giving C2H3+ in association with C2H4 is shown to emerge at both high internal excitation of C2H5+ and high collision energies. From CS measurements, energy-dependent total rate constants in the range 4.3×10-11-5.2×10-10 cm3·molecule-1·s-1 have been obtained. Theoretical calculations indicate that both channels stem from a common covalently bound intermediate, CH3CH2CHCH+, from which barrierless and exothermic pathways exist for the production of both cyclic c-C3H3+ and linear H2CCCH+ isomers of the main product channel. For the minor C4H5+ product, two isomers are energetically accessible: the three-member cyclic isomer c-C3H2(CH3)+ and the higher energy linear structure CH2CHCCH2+, but their formation requires multiple isomerization steps and passages via transition states lying only 0.11 eV below the reagents' energy, thus explaining the smaller BR. Results have implications for the modeling of hydrocarbon chemistry in the interstellar medium and the atmospheres of planets and satellites as well as in laboratory plasmas (e.g., plasma-enhanced chemical vapor deposition of carbon nanotubes and diamond-like carbon films).

Dataset Information

Elusive Co2O3: A Combined Experimental and Theoretical Study.

Publications

Elusive Co<sub>2</sub>O<sub>3</sub>: A Combined Experimental and Theoretical Study.

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