The Energetics of the Hydrogenation of a Single-Walled Carbon Nanotube

Janet RyuProfessor Nicola Marzari

May 10, 20053.021J

Outline

• What are carbon nanotubes?

• Quantum mechanical approaches used.

• Models of carbon nanotubes.

• Calculations and results

• Potential future work with the attachment of

organic sidegroups to carbon nanotubes.

Carbon Nanotubes (CNT)• Created by rolling a sheet

of graphite into a

cylinder.

• Hexagonal lattice.

• Armchair and Zigzag

http://common.ziffdavisinternet.com/util_get_image/2/0,1311,sz=1&i=25371,00.jpg

http://www.udel.edu/PR/UDaily/2004/Chou-Atomic-Structureslg.jpg

Zigzag and Armchair?

http://www.pa.msu.edu/cmp/csc/ntproperties/

• Type of CNT

depends on the

angle between R

and armchair.

• na1 + ma2 = R

• Chirality, or twist,

depends on n and

m.

Properties of Carbon Nanotubes

• Extremely small.

• Strong and flexible structures.

• Efficient heat conductors along

tube.

• Unique electrical properties.

• Superconducting, insulating,

semiconducting or conducting. http://www.lce.hut.fi/publications/annual2001/node12.html

Quantum Mechanical Methods

• Study infinite systems.

• Density Functional

Theory

• PWscf (Plane-Wave Self-Consistent

Field)

• Use PWscf to calculate energies.

• Find which geometry has minimum

energy.

http://www.uncp.edu/

home/mcclurem/lattice/lattice.html

http://www.uncp.edu/home/mcclurem/lattice/lattice.html

Diamond

Lattice constant, A=6.73 bohr, at 300 K.Source: Sze, S.M., Physics of Semiconductor Devices, New York, Wiley

Interscience Publication, 1981, pp. 848-849.

Carbon Nanotube

Creation of CNT Model with XCrySDen

Application for visualizing crystalline and molecular structures. Makes it possible to check that the geometry is described correctly.

Functionalized CNT with 2 Hydrogens

Fully Hydrogenated CNT

2 rings of a 5,0 CNT fully hydrogenated.

Energies of a 5,0 CNT and H2

Hydrogen molecule

5,0 CNT E(CNT) = -

227.15609 rydE(H2) = -2.33059 ryd

Energies of a Functionalized CNT

E(CNT + 2H) = -229.53916 ryd

-229.50896 ryd

-229.52976 ryd

Results

Energy required to functionalize a 5,0 CNT with 2H is given by:

Ef = E(CNT + 2H) – E(CNT) –E(H2) Ef = -0.05248 ryd

Since Ef < 0, E(CNT + 2H) is at lower energy. Hydrogenation of the CNT is thermodynamically favored.

Future Work

• Study the physical properties and

characteristics of a hydrogenated

CNT.

• Create a thermodynamical model.

• Applications

• Ultra-small electronics

• Biomedical

• Microscopyhttp://www.fna.muohio.edu/amu/nano/ewels.html

Nanotube above with Galaxy, Route to the Stars 2

Acknowledgments

I would like to thank Professor Nicola Marzari and Young-Su Lee for their guidance and help in completing this project. I would also like to thank my classmate Adam Chao for his assistance.