Deepak Srivastava Computational Nanotechnology at CSC/NAS NASA Ames Research Center Moffett Field, CA 95014 Collaborators: M. Menon – University of Kentucky K. Cho – Stanford University D. Brenner – NC State University R. Ruoff – Northwestern University M. Osman – Washington State University Computational Nanotechnology of Materials, Devices and Machines: Carbon Nanotubes
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Deepak Srivastava Computational Nanotechnology at CSC/NAS NASA Ames Research Center Moffett Field, CA 95014 Collaborators: M. Menon – University of Kentucky.
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Deepak Srivastava
Computational Nanotechnology at CSC/NAS
NASA Ames Research Center
Moffett Field, CA 95014
Collaborators:M. Menon – University of KentuckyK. Cho – Stanford UniversityD. Brenner – NC State UniversityR. Ruoff – Northwestern UniversityM. Osman – Washington State University
Computational Nanotechnology of Materials, Devices and Machines: Carbon Nanotubes
http://www.ipt.arc.nasa.gov at Ames Research Center
Simulation Techniques
•Large scale Classical Molecular Dynamics Simulations on a SharedMemory Architecture Computer
• Tersoff-Brenner reactive many-body potential for hydrocarbons
with long range LJ(6-12) Van der Walls interactions
• Parallel implementation on a shared memory Origin2000
• Quantum Molecular Dynamics Simulations
• Tight-binding MD in a non-orthogonal atomic basis
• Previous parametrization: silicon and carbon (M. Menon and K. R
Subbaswami, Phys. Rev. B 1993-94.
• Extended to heteroatomic systems including C, B, N, H
Experimental Nanotechnology at Ames Research Center
http://www.ipt.arc.nasa.gov at Ames Research Center
Nanomechanics of Nanomaterials
• Nanotubes are extremely strong highly elastic nanofibers
~ High value of Young’s Modulus (1.2 -1.3 T Pa for SWNTs)
~ Elastic limit upto 10-15% strain
• Dynamic response under axial compression, bending torsion
• redistribution of strain• sharp buckling leading to bond rupture• SWNT is stiffer than MWNT
Nanomechanics of Nanomaterials
Nanotubes in Composites
• Experiment: buckling and collapse of nanotubes embedded in polymer composites.
Buckle, bend andloops of thicktubes..
Local collapse orfracture of thintubes.
Stiffness and Plasticity of Compressed C Nanotubes
Plastic Collapse of an (8,0) Carbon Nanotube
Quantum Molecular Dynamics
•D. Srivastava, M. Menon and K. Cho, Phys. Rev. Lett. (1999)
Plastic Collapse by Design
• Tube plastically collapses at the location of the defect• New types of heterojunctions can be created • Quantum dot effect in one dimensional system
CxByNz Nanotubes
• Band gap engineering over a larger range
• BN ~ 5 eV• BC2N ~ 2 eV• C ~ 0 - 1 eV• BC3 ~ 0.5 eV