Nitrogen substitution of carbon in graphite: Structure evolution toward molecular forms

Santos, M. C. dos; Alvarez, F.

doi:10.1103/physrevb.58.13918

Cited by 153 publications

(106 citation statements)

References 19 publications

(17 reference statements)

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“…12 The decrease in the formation energy from graphite to the ͑5, 5͒ tube is consistent with the proposal that N atom prefers a nonplanar surrounding in the graphitic materials, 33,34 although the actual buckling occurs at concentrations of N atoms exceeding 20%. 33 Calculations for ͑7,0͒ and ͑9,0͒ SWNTs gave 1.24 and 1.61 eV, respectively, which further validates this assumption. For B dopant atoms, the cost of substitution is 3.64 eV for graphite and 3.08 eV for a ͑5,5͒ SWNTs.…”

Section: B Density Functional Theory Calculations Of Dopant Atomnanosupporting

confidence: 84%

B and N ion implantation into carbon nanotubes: Insight from atomistic simulations

Kotakoski

Krasheninnikov

et al. 2005

Phys. Rev. B

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By employing atomistic computer simulations with empirical potential and density functional force models, we study B / N ion implantation onto carbon nanotubes. We simulate irradiation of single-walled nanotubes with B and N ions and show that up to 40% of the impinging ions can occupy directly the sp 2 positions in the nanotube atomic network. We further estimate the optimum ion energies for direct substitution. Ab initio simulations are used to get more insight into the structure of the typical atomic configurations which appear under the impacts of the ions. As annealing should further increase the number of sp 2 impurities due to dopant atom migration and annihilation with vacancies, we also study migration of impurity atoms over the tube surface. Our results indicate that irradiation-mediated doping of nanotubes is a promising way to control the nanotube electronic and even mechanical properties due to impurity-stimulated crosslinking of nanotubes.

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Section: B Density Functional Theory Calculations Of Dopant Atomnanosupporting

confidence: 84%

B and N ion implantation into carbon nanotubes: Insight from atomistic simulations

Kotakoski

Krasheninnikov

et al. 2005

Phys. Rev. B

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“…This observation would support previous quantum chemical calculations indicating that the nitrogen atoms prefer a nonplanar surrounding. 4,17 Apart from the distortedgraphitic phase, we also observed regions on the 350°C grown CN x films consisting of graphitic planes that appears to be cross linked and intersected, as shown in Fig. 4͑b͒.…”

Section: Carbon Nitride Filmsmentioning

confidence: 75%

In situscanning tunneling microscopic and spectroscopic investigation of magnetron-sputtered C and CN thin films

et al. 2000

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Carbon and carbon nitride films, grown in argon or nitrogen discharges by reactive dc magnetron sputtering of a graphite target, were characterized by in situ scanning tunneling microscopy. When the growth temperature increased from ambient to 800°C, we observed a topographic evolution of the carbon films from an amorphous to a graphitelike structure, and further to a distorted-graphitic phase with curved and intersecting basal planes, and finally to a surface containing nanotubes and nanodomes. When nitrogen was incorporated into the films, distortion of the graphitic basal planes occurred at a lower temperature compared to the pure carbon case. At temperatures of ϳ200°C and above, regions of a nongraphitic phase, containing a high degree of carbon sp 3 bonds were observed. Spatially resolved tunneling spectroscopic measurements indicated that the band gaps were 0, ϳ0-0.6 eV, and ϳ0.4-2.0 eV for graphitelike structures, the distorted-graphitic phase, and the nongraphitic phase, respectively. Together with ex situ x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy measurements, the results suggest that the incorporation of nitrogen promotes bending of the graphitic basal planes and thereby facilitates the formation of three-dimensional covalently bonded networks with a high degree of sp 3 -coordinated carbon atoms.

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“…2). When a nitrogen atom substitutes for carbon in a hexagonal structure, it shares the same sp 2 -hybridization as neighboring carbon atoms, and its remaining two electrons participate in the delocalized π-electron network as described, for instance, in graphite (Dos Santos and Alvarez, 1998), fullerene (Reuther and Hirsch, 2000), and carbon nanotubes (Choi et al, 2005). Three-coordinated N prefers a locally 'buckled', non-planar structure.…”

Section: Anthracitementioning

confidence: 99%

Organic nitrogen chemistry during low-grade metamorphism

Boudou

Schimmelmann

Ader

et al. 2008

Geochimica et Cosmochimica Acta

130

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-Most of the organic nitrogen (N org ) on Earth is disseminated in crustal sediments and rocks in the form of fossil nitrogen-containing organic matter. The chemical speciation of fossil N org within the overall molecular structure of organic matter changes with time and heating during burial. Progressive thermal evolution of organic matter involves phases of enhanced elimination of N org and ultimately produces graphite containing only traces of nitrogen. Long-term chemical and thermal instability makes the chemical speciation of N org a valuable tracer to constrain the history of sub-surface metamorphism and to shed light on the subsurface biogeochemical nitrogen cycle and its participating organic and inorganic nitrogen pools. This study documents the evolutionary path of N org speciation, transformation and elimination before and during metamorphism and advocates the use of XRay Photoelectron Spectroscopy (XPS) to monitor changes in N org speciation as a diagnostic tool for organic metamorphism. Our multidisciplinary evidence from XPS, stable isotopes, traditional quantitative coal analyses, and other analytical approaches shows that at the metamorphic onset N org is dominantly present as pyrrolic and pyridinic nitrogen. The relative abundance of nitrogen substituting for carbon in condensed, partially aromatic systems (where N is covalently bonded to three C atoms) increases exponentially with increasing metamorphic grade, at the expense of pyridinic and pyrrolic nitrogen. At the same time, much N org is eliminated without significant nitrogen isotope fractionation. The apparent absence of Rayleigh-type nitrogen isotopic fractionation suggests that direct thermal loss of nitrogen from an organic matrix does not serve as a major pathway for N org elimination. Instead, we propose that hot H, O-containing fluids or some of their components gradually penetrate into the carbonaceous matrix and eliminate N org along a progressing reaction front, without causing nitrogen isotope fractionation in the residual N org in the unreacted core of the carbonaceous matrix. Before the reaction front can reach the core, an increasing part of core N org chemically stabilizes in the form of nitrogen atoms substituting for carbon in condensed, partially aromatic systems forming graphite-like structural domains with delocalized π-electron systems (nitrogen atoms substituting for "graphitic" carbon in natural metamorphic organic matter). Thus, this nitrogen species with a conservative isotopic composition is the dominant form of residual nitrogen at higher metamorphic grade.

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Nitrogen substitution of carbon in graphite: Structure evolution toward molecular forms

Cited by 153 publications

References 19 publications

B and N ion implantation into carbon nanotubes: Insight from atomistic simulations

B and N ion implantation into carbon nanotubes: Insight from atomistic simulations

In situscanning tunneling microscopic and spectroscopic investigation of magnetron-sputtered C and CN thin films

Organic nitrogen chemistry during low-grade metamorphism

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