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, J
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 /util_get_image/2/0,1311,sz=1&i=2 5371,00.jpg w.udel.e du/PR/U Daily/20 04/Chou- Atomic- Structure slg.jpg
Zigzag and Armchair? 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. 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. 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
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 H 2 Hydrogen molecule 5,0 CNT E(CNT) = ryd E(H2) = ryd
Energies of a Functionalized CNT E(CNT + 2H) = ryd ryd 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 = 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 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.