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.