156
7 Carbon Allotropes
energy between the present results and previous observations evidences sufficiently
the accuracy and reliability of the BOLS-TB-ZPS derivatives.
The ratio of the energy shift between the 2- and the 3-coordinated atoms (252/169
= 149%) and the bond contraction of monolayer graphene (18.5%) agrees exceedingly well with that observed from monolayer graphene [49]. The C–C bond contracts
by 14.7% from 0.246 to 0.207 nm and the minimal energy (7.50 eV/bond) required
for breaking a bond between two-coordinated carbon atoms is 32% times higher
than that (5.67 eV/bond) required for breaking a bond between three-coordinated
carbon atoms in a suspended graphene. Information in Table 7.2 further confirms
BOLS-NEP derivatives on the CN dependence of the Raman shift [122, 123]. With
the known bond length, bond energy, effective CN, one is able to derive the local
energy density E den and atomic cohesive energy E coh at different atomic sites of
carbon allotropes.
Most strikingly, only one neighbor loss makes a great difference between C atoms
at edges and C atoms in the monolayer skin. The defected P states of C are the same
to Rh, Au, Ag, Cu and W adatoms or terrace edges and the skin entrapment is the
same to Pt, Re, and Co adatoms or nanocrystals.
7.5 Summary
BOLS-NEP incorporation into the STM/S, TEM, and ZPS has enabled comprehensive information of the local bond length, bond energy, energy density, and cohesive
energy at GNR edges, point defects, and monolayer skin of graphite. As compared
in Fig. 7.1, STM protrusions and STS resonant peaks of vacancy defects at graphite
surface are naturally the same to that of the graphene zigzag edge. One can therefore
focus on the graphite surface vacancy more conveniently to mimic the GNR edge,
as the latter is hardly accurately detectable in measurements. One neighbor loss differentiates greatly the edge carbon atom from the skin atom in the entrapment or
the polarization dominance. Importantly, the practice clarifies the mechanism and
dynamics of DFs creation. Polarization of the dangling-bond electrons by the locally
densely entrapped bonding electrons dictates the unusual performance of GNRs.
References
1. S. Iijima, Helical microtubes of graphitic carbon. Nature 354(6348), 56–58 (1991)
2. H.J. Dai, J.H. Hafner, A.G. Rinzler, D.T. Colbert, R.E. Smalley, Nanotubes as nanoprobes in
scanning probe microscopy. Nature 384(6605), 147–150 (1996)
3. P.G. Collins, A. Zettl, Unique characteristics of cold cathode carbon-nanotube-matrix field
emitters. Phys. Rev. B 55(15), 9391–9399 (1997)
4. W.A. Deheer, A. Chatelain, D. Ugarte, Acarbon nanotube field-emission electron cource.
Science 270(5239), 1179–1180 (1995)
7 Carbon Allotropes
energy between the present results and previous observations evidences sufficiently
the accuracy and reliability of the BOLS-TB-ZPS derivatives.
The ratio of the energy shift between the 2- and the 3-coordinated atoms (252/169
= 149%) and the bond contraction of monolayer graphene (18.5%) agrees exceedingly well with that observed from monolayer graphene [49]. The C–C bond contracts
by 14.7% from 0.246 to 0.207 nm and the minimal energy (7.50 eV/bond) required
for breaking a bond between two-coordinated carbon atoms is 32% times higher
than that (5.67 eV/bond) required for breaking a bond between three-coordinated
carbon atoms in a suspended graphene. Information in Table 7.2 further confirms
BOLS-NEP derivatives on the CN dependence of the Raman shift [122, 123]. With
the known bond length, bond energy, effective CN, one is able to derive the local
energy density E den and atomic cohesive energy E coh at different atomic sites of
carbon allotropes.
Most strikingly, only one neighbor loss makes a great difference between C atoms
at edges and C atoms in the monolayer skin. The defected P states of C are the same
to Rh, Au, Ag, Cu and W adatoms or terrace edges and the skin entrapment is the
same to Pt, Re, and Co adatoms or nanocrystals.
7.5 Summary
BOLS-NEP incorporation into the STM/S, TEM, and ZPS has enabled comprehensive information of the local bond length, bond energy, energy density, and cohesive
energy at GNR edges, point defects, and monolayer skin of graphite. As compared
in Fig. 7.1, STM protrusions and STS resonant peaks of vacancy defects at graphite
surface are naturally the same to that of the graphene zigzag edge. One can therefore
focus on the graphite surface vacancy more conveniently to mimic the GNR edge,
as the latter is hardly accurately detectable in measurements. One neighbor loss differentiates greatly the edge carbon atom from the skin atom in the entrapment or
the polarization dominance. Importantly, the practice clarifies the mechanism and
dynamics of DFs creation. Polarization of the dangling-bond electrons by the locally
densely entrapped bonding electrons dictates the unusual performance of GNRs.
References
1. S. Iijima, Helical microtubes of graphitic carbon. Nature 354(6348), 56–58 (1991)
2. H.J. Dai, J.H. Hafner, A.G. Rinzler, D.T. Colbert, R.E. Smalley, Nanotubes as nanoprobes in
scanning probe microscopy. Nature 384(6605), 147–150 (1996)
3. P.G. Collins, A. Zettl, Unique characteristics of cold cathode carbon-nanotube-matrix field
emitters. Phys. Rev. B 55(15), 9391–9399 (1997)
4. W.A. Deheer, A. Chatelain, D. Ugarte, Acarbon nanotube field-emission electron cource.
Science 270(5239), 1179–1180 (1995)