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The Energetics of the Hydrogenation of a Single- Walled Carbon Nanotube Janet Ryu Professor Nicola Marzari May 10, 2005 3.021J

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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.

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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=2 5371,00.jpg http://ww w.udel.e du/PR/U Daily/20 04/Chou- Atomic- Structure slg.jpg

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Zigzag and Armchair? http://www.pa.msu.edu/cmp/csc/ntprop erties/ Type of CNT depends on the angle between R and armchair. na 1 + ma 2 = R Chirality, or twist, depends on n and m.

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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/publ ications/annual2001/nod e12.html

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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/ho me/mcclurem/lattice/latt ice.html

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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.

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Carbon Nanotube

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Creation of CNT Model with XCrySDen Application for visualizing crystalline and molecular structures. Makes it possible to check that the geometry is described correctly.

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Functionalized CNT with 2 Hydrogens

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Fully Hydrogenated CNT 2 rings of a 5,0 CNT fully hydrogenated.

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Energies of a 5,0 CNT and H 2 Hydrogen molecule 5,0 CNT E(CNT) = - 227.15609 ryd E(H2) = -2.33059 ryd

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Energies of a Functionalized CNT E(CNT + 2H) = - 229.53916 ryd -229.50896 ryd -229.52976 ryd

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Results Energy required to functionalize a 5,0 CNT with 2H is given by: E f = E(CNT + 2H) – E(CNT) –E(H2) E f = -0.05248 ryd Since E f < 0, E(CNT + 2H) is at lower energy. Hydrogenation of the CNT is thermodynamically favored.

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Future Work Study the physical properties and characteristics of a hydrogenated CNT. Create a thermodynamical model. Applications Ultra-small electronics Biomedical Microscopy http://www.fna.muohio.edu/amu/nano/ewels.html Nanotube above with Galaxy, Route to the Stars 2

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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.

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