From Graphite to carbon nanotubes. A guide for itsFrom Graphite to carbon nanotubes. A guide for its applications on nanoscience and nanotechnology applications on nanoscience and nanotechnology

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DISTANCIA (u.a.) DEL EJE DEL NANOTUBO (6,6) AL ÁTOMO DE PLOMO

Juan Salvador Arellano Peraza Juan Salvador Arellano Peraza

Área de Física Atómica Molecular Aplicada, Universidad Autónoma Metropolitana Azcapotzalco, C.P. 02200, México D.F., MéxicoÁrea de Física Atómica Molecular Aplicada, Universidad Autónoma Metropolitana Azcapotzalco, C.P. 02200, México D.F., México

MotivationMotivation

Graphene, has been obtained (year 2004). This is a 2D and only one atom thick material. It 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 can be converted to 0D buckyballas, 1D nanotubes or stacked in the best known 3D graphite. See Figure 1.graphite. See Figure 1.

Graphite is formed by weakly interacting parallel planar carbon layers. Atoms and 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 molecules can be intercalated between those layers giving rise to a variety of intercalated intercalated compoundscompounds..

ConclusionsConclusions

Density Functional Formalism: Density Functional Formalism: FHI96MD codeFHI96MD code Exchange-Correlation Exchange-Correlation functional: Local Density functional: Local Density ApproximationApproximation Nonlocal norm-conserving Nonlocal norm-conserving pseudopotential of Hamman et pseudopotential of Hamman et al. for Carbon (4 valence al. for Carbon (4 valence electrons)electrons) All electron description of All electron description of Lithium for all the lithium Lithium for all the lithium intercalated compounds.intercalated compounds.

Pb difussion along the /6,6) carbon nanotubePb difussion along the /6,6) carbon nanotube

2mev/atom: energy difference between graphite and graphene2mev/atom: energy difference between graphite and graphene

LiCLiC66

It is the richest Li compound existing at normal pressure It is the richest Li compound existing at normal pressure

Stage-1 compoundStage-1 compound

AA stacking of the graphene layersAA stacking of the graphene layers

The Li atoms are placed midway between two parallel The Li atoms are placed midway between two parallel hexagons, above the center of the hexagonhexagons, above the center of the hexagon

Only one third of those positions are occupied by LiOnly one third of those positions are occupied by Li

LiCLiC22

This compound forms only by high pressure synthesisThis compound forms only by high pressure synthesis

Experimental phase: AA stacking of the graphene layersExperimental phase: AA stacking of the graphene layers

The Li atoms are placed midway between two parallel hexagons, above the center of the hexagonThe 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

LiCLiC33

Li midway between graphene layers

Li up and down the middle

relaxed Li positions

Superdense compound formed by ball-milling; it is stable under ambient pressureSuperdense compound formed by ball-milling; it is stable under ambient pressure

The X-ray diffraction pattern indicates Li atoms at The X-ray diffraction pattern indicates Li atoms at ±± 0.83 au from the medium plane between 0.83 au from the medium plane between the graphene layersthe graphene layers

Adequate description of graphite Adequate description of graphite (AB packing, cohesion, compressibility)(AB packing, cohesion, compressibility) by DFT-LDA calculations by DFT-LDA calculations

Li intercalation changes the stacking of C layers from AB in graphite to AA in Li compoundsLi intercalation changes the stacking of C layers from AB in graphite to AA in Li compounds

The distance between graphene layers increases and the uniaxial compressibility decreases in The distance between graphene layers increases and the uniaxial compressibility decreases in LiCLiC66 with respect to pure graphite with respect to pure graphite

DFT underestmates the expansion of the lattice and the uniaxial compressibility of LiCDFT underestmates the expansion of the lattice and the uniaxial compressibility of LiC22 as as

compared to the experimental values. compared to the experimental values. Assuming AB stacking, we recover the experimental expansion of the 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 stackinglattice but the value of the uniaxial compressibility is similar (small) to that obtained with AA stacking

DFT calculations do not predict separation of the Li atoms from the medium plane between DFT calculations do not predict separation of the Li atoms from the medium plane between graphene layers in the LiCgraphene layers in the LiC33 compounds compounds

It has been given a brief scope of the possible applications of the graphene, graphite and It 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. carbonaceous materials as can be the design of new lithium batteries or the hydrogen storage. ¡There are many more applications under development!¡There are many more applications under development!

AB stacking, is the most abundant form AB stacking, is the most abundant form of graphite (circles)of graphite (circles)

AA stacking (two adjacent graphene AA stacking (two adjacent graphene layers), present in the intercalated layers), present in the intercalated compounds (triangles)compounds (triangles)

[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. 2281-2288.[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.

Hydrogen molecule adsorption on nanotube Hydrogen molecule adsorption on nanotube

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.

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DISTANCIA (u.a.) DE LA HOJA DE GRAFENO (CELDA 2X2) AL ÁTOMO DE PLOMO

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].