Presentation on theme: "The Energetics of the Hydrogenation of a Single- Walled Carbon Nanotube Janet Ryu Professor Nicola Marzari May 10, 2005 3.021J."— Presentation transcript:
The Energetics of the Hydrogenation of a Single- Walled Carbon Nanotube Janet Ryu Professor Nicola Marzari May 10, 2005 3.021J
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=2 5371,00.jpg http://ww w.udel.e du/PR/U Daily/20 04/Chou- Atomic- Structure slg.jpg
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.
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
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
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.
Fully Hydrogenated CNT 2 rings of a 5,0 CNT fully hydrogenated.
Energies of a 5,0 CNT and H 2 Hydrogen molecule 5,0 CNT E(CNT) = - 227.15609 ryd E(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: 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.
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
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.