From Graphite to carbon nanotubes. A guide for its
applications on nanoscience and nanotechnology
Juan Salvador Arellano Peraza
Área de Física Atómica Molecular Aplicada, Universidad Autónoma Metropolitana Azcapotzalco, C.P. 02200, México D.F., México
2mev/atom: energy difference between graphite and graphene
Motivation
* Graphene, has been obtained (year 2004). This is a 2D and only one atom thick material.
It can be converted to 0D buckyballas, 1D nanotubes or stacked in the best known 3D
graphite. See Figure 1.
* Graphite is formed by weakly interacting parallel planar carbon layers. Atoms and
molecules can be intercalated between those layers giving rise to a variety of intercalated
compounds.
[1]
Figure 1
Figure 2
[2]
AB stacking, is the most abundant form
of graphite (circles)
rDensity Functional
Formalism: FHI96MD code
rExchange-Correlation
functional: Local Density
Approximation
rNonlocal norm-conserving
pseudopotential of Hamman et
al. for Carbon (4 valence
electrons)
rAll electron description of
Lithium for all the lithium
intercalated compounds.
Hydrogen molecule adsorption on nanotube
AA stacking (two adjacent graphene
layers), present in the intercalated
compounds (triangles)
LiC6
[3]
[3]
It is the richest Li compound existing at normal pressure
Stage-1 compound
AA stacking of the graphene layers
The Li atoms are placed midway between two parallel
hexagons, above the center of the hexagon
Only one third of those positions are occupied by Li
[2]
LiC2
[3]
This compound forms only by high pressure synthesis
Experimental phase: AA stacking of the graphene layers
The Li atoms are placed midway between two parallel hexagons, above the center of the hexagon
circles: AA stacking
stars: AB stacking
circles: AA stacking
stars: AB stacking
LiC3
Superdense compound formed by ball-milling; it is stable under ambient pressure
-49.22
-140.70
ENERGÍA POTENCIAL TOTAL (u.a.)
ENERGÍA POTENCIAL TOTAL (u.a.)
Pb difussion along the /6,6) carbon nanotube
-140.72
-140.74
-140.76
The X-ray diffraction pattern indicates Li atoms at ± 0.83 au from the medium plane between
the graphene layers
-49.24
-49.26
-49.28
Li midway between graphene layers
-49.30
Li up and down the middle
-49.32
relaxed Li positions
-49.34
2
-140.78
0
5
10
15
20
4
6
8
10
12
14
16
DISTANCIA (u.a.) DE LA HOJA DE GRAFENO (CELDA 2X2) AL ÁTOMO DE PLOMO
DISTANCIA (u.a.) DEL EJE DEL NANOTUBO (6,6) AL ÁTOMO DE PLOMO
The binding energy for the
Pb atom on the (6,6)
carbon nanotube axis is
0.27 eV.
The initial calculations for
the difussion of the Pb
atom along the carbon
nanotube axis shows that
this could be and easy
process, that is, without
barrier energies.
Pb atom adsorption on a graphene layer. The
figure shows there are 8 carbon atoms per one
Pb atom. The atom is adsorbed at a distance
of 4.8 a.u., a little less than the equilibrium
distance for the hydrogen molecule above the
graphene layer, 5.07 a.u. These result was
reported on reference [4].
[1] A. K. Geim and K.S. Novoselov. Nature materials, Vol. 6,
March 2007, p. 183.
[2] J. S. Arellano, L.M. Molina, A. Rubio, M.J. López and J. A.
Alonso. J. Chem. Phys. Vol. 117, No. 5, 1 August 2002, p. 22812288.
[3] Juan Salvador Arellano Peraza, L. M. Molina, M. J. López, A.
Rubio y J. A.. Alonso. “Resultados para litio intercalado en grafito,
LiC2 y LiC6 usando teoría de funcionaled de la densidad”.
Memoria de la XIV Semana de la Docencia e Investigación en
Química. Universidad Autónoma Metropolitana-Azcapotzalco,
año 2001,p.113-123.
[4] J. S. Arellano, L.M. Molina, A. Rubio, and J. A. Alonso. J.
Chem. Phys. Vol. 112, Number 18, 8 May 2000, p. 8114-8119.
Conclusions
rAdequate description of graphite (AB packing, cohesion, compressibility) by DFT-LDA calculations
rLi intercalation changes the stacking of C layers from AB in graphite to AA in Li compounds
rThe distance between graphene layers increases and the uniaxial compressibility decreases in
LiC6 with respect to pure graphite
rDFT underestmates the expansion of the lattice and the uniaxial compressibility of LiC2 as
compared to the experimental values. Assuming AB stacking, we recover the experimental expansion of the
lattice but the value of the uniaxial compressibility is similar (small) to that obtained with AA stacking
rDFT calculations do not predict separation of the Li atoms from the medium plane between
graphene layers in the LiC3 compounds
rIt has been given a brief scope of the possible applications of the graphene, graphite and
carbonaceous materials as can be the design of new lithium batteries or the hydrogen storage.
¡There are many more applications under development!