Density Functional Theory versus Complete Active Space Self-Consistent Field Investigation of the Half-Metallic Character of Graphite-Like and Amorphous Carbon Nanoparticles

Khavryuchenko, Oleksiy V.; Khavryuchenko, V. D.; Peslherbe, Gilles H.

doi:10.1021/jp502207n

Cited by 7 publications

(9 citation statements)

References 32 publications

(40 reference statements)

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“…3 Two independent theoretical studies have shown that amorphous carbon nanoparticles with low or no hydrogen-content might even be (semi-)metallic. 14,15 In stark contrast, we consider hydrogen passivated structures that feature large band gaps because these are better models for the real situation, in which nonfunctionalized carbon surfaces and edges are unlikely.…”

Section: Introductionmentioning

confidence: 99%

The Electronic Structure of Amorphous Carbon Nanodots

et al. 2015

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We have studied hydrogen-passivated amorphous carbon nanostructures with semiempirical molecular orbital theory in order to provide an understanding of the factors that affect their electronic properties. Amorphous structures were first constructed using periodic calculations in a melt/quench protocol. Pure periodic amorphous carbon structures and their counterparts doped with nitrogen and/or oxygen feature large electronic band gaps. Surprisingly, descriptors such as the elemental composition and the number of sp(3)-atoms only influence the electronic structure weakly. Instead, the exact topology of the sp(2)-network in terms of effective conjugation defines the band gap. Amorphous carbon nanodots of different structures and sizes were cut out of the periodic structures. Our calculations predict the occurrence of localized electronic surface states, which give rise to interesting effects such as amphoteric reactivity and predicted optical band gaps in the near-UV/visible range. Optical and electronic gaps display a dependence on particle size similar to that of inorganic colloidal quantum dots.

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Section: Introductionmentioning

confidence: 99%

The Electronic Structure of Amorphous Carbon Nanodots

et al. 2015

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“…The properties of the C4Q2 cluster are analogous to that of the G‐4H bare‐edge cluster described in Ref. . The cluster is paramagnetic and half‐metallic with pseudo‐degenerate spin states, that is, the singlet and triplet states are almost equal in energy.…”

Section: Resultsmentioning

confidence: 60%

Spin Catalysis over Conductive Solids: Enhancing the Rate of Model C−C Bond Cracking over Carbon Nanoparticles

Khavryuchenko

Peslherbe

2016

ChemCatChem

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The concept of catalysis over a spin‐conductive mediator is investigated with quantum‐chemical calculations. Specifically, homolytic C−C bond cleavage in ethane over small edge‐oxidized half‐metallic carbon clusters in the presence of a methyl radical was considered with the complete active space self‐consistent field method. The methyl radical (spin catalyst) and carbon cluster (mediator) are found to share a common electronic orbital containing the radical unpaired electron, allowing nascent radicals emerging from ethane dissociation to interact with the spin catalyst through the carbon electronic system. This could result in spin flip, affording formation of a triplet radical pair not prone to recombination and thus resulting in the acceleration of the reaction rate. This demonstrates that new pathways may open up in controlled catalytic processes by allowing normally spin‐forbidden reactions and not necessarily lowering activation barriers in the traditional sense of catalysis.

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“…An analogous situation was reported previously for polyconjugated carbon materials. 44 Some prompts for appropriate selection can be derived from analysis of the electronic structure of the neutral forms of the complexes. The ''additional'' electron should occupy a spin-up LUMO or spin-down LUMO of the species, so comparison of their energies (Table 4) can indicate the preferable multiplicity of the reduced state.…”

Section: Modeling Of Complex Reductionmentioning

confidence: 99%

Modeling of catalytically active metal complex species and intermediates in reactions of organic halides electroreduction

Lytvynenko

Kolotilov

Кискин

et al. 2015

Phys. Chem. Chem. Phys.

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The results of quantum chemical modeling of organic and metal-containing intermediates that occur in electrocatalytic dehalogenation reactions of organic chlorides are presented. Modeling of processes that take place in successive steps of the electrochemical reduction of representative C1 and C2 chlorides - CHCl3 and Freon R113 (1,1,2-trifluoro-1,2,2-trichloroethane) - was carried out by density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2). It was found that taking solvation into account using an implicit solvent model (conductor-like screening model, COSMO) or considering explicit solvent molecules gave similar results. In addition to modeling of simple non-catalytic dehalogenation, processes with a number of complexes and their reduced forms, some of which were catalytically active, were investigated by DFT. Complexes M(L1)2 (M = Fe, Co, Ni, Cu, Zn, L1H = Schiff base from 2-pyridinecarbaldehyde and the hydrazide of 4-pyridinecarboxylic acid), Ni(L2) (H2L2 is the Schiff base from salicylaldehyde and 1,2-ethylenediamine, known as salen) and Co(L3)2Cl2, representing a fragment of a redox-active coordination polymer [Co(L3)Cl2]n (L3 is the dithioamide of 1,3-benzenedicarboxylic acid), were considered. Gradual changes in electronic structure in a series of compounds M(L1)2 were observed, and correlations between [M(L1)2](0) spin-up and spin-down LUMO energies and the relative energies of the corresponding high-spin and low-spin reduced forms, as well as the shape of the orbitals, were proposed. These results can be helpful for determination of the nature of redox-processes in similar systems by DFT. No specific covalent interactions between [M(L1)2](-) and the R113 molecule (M = Fe, Co, Ni, Zn) were found, which indicates that M(L1)2 electrocatalysts act rather like electron transfer mediators via outer-shell electron transfer. A relaxed surface scan of the adducts {M(L1)2·R113}(-) (M = Ni or Co) versus the distance between the chlorine atom leaving during reduction and the corresponding carbon atom showed an energy barrier to electron transfer (the first stage of R113 catalytic reduction), while DFT optimization of the {Ni(L2)·R113}(-) adduct showed barrier-free decomposition. The difference between the stabilities of the {Ni(L1)2·R113}(-) and {Ni(L2)·R113}(-) adducts correlates with the difference between the catalytic activities of Ni(L1)2 and Ni(L2) in the electrochemical reduction of R113.

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Density Functional Theory versus Complete Active Space Self-Consistent Field Investigation of the Half-Metallic Character of Graphite-Like and Amorphous Carbon Nanoparticles

Cited by 7 publications

References 32 publications

The Electronic Structure of Amorphous Carbon Nanodots

The Electronic Structure of Amorphous Carbon Nanodots

Spin Catalysis over Conductive Solids: Enhancing the Rate of Model C−C Bond Cracking over Carbon Nanoparticles

Modeling of catalytically active metal complex species and intermediates in reactions of organic halides electroreduction

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