Deepak Srivastava

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Computational Nanotechnology of Materials,
Devices and Machines Carbon Nanotubes

• 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
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http//www.ipt.arc.nasa.gov at Ames Research
Center
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Simulation Techniques

• Large scale Classical Molecular Dynamics
  Simulations on a Shared
• Memory 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

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Experimental Nanotechnology at Ames Research
Center
http//www.ipt.arc.nasa.gov at Ames Research
Center
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Nanomechanics of Nanomaterials

• Nanotubes are extremely strong highly elastic
  nanofibers

High value of Youngs 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

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Nanomechanics of Nanomaterials
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Nanotubes in Composites

• Experiment buckling and collapse of nanotubes
  embedded
• in polymer composites.

Local collapse or fracture of thin tubes.
Buckle, bend and loops of thick tubes..
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Stiffness and Plasticity of Compressed C Nanotubes
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Plastic Collapse of an (8,0) Carbon Nanotube
Quantum Molecular Dynamics

• D. Srivastava, M. Menon and K. Cho, Phys. Rev.
  Lett. (1999)

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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

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CxByNz Nanotubes

• Band gap engineering over a larger range

• BN 5 eV
• BC2N 2 eV
• C 0 - 1 eV
• BC3 0.5 eV

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BN Nanotubes - Structural Characteristics

• BN bond buckling effect

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BN Nanotubes Nanomechanics and Plasticity

• Comparison of Youngs modulus and elastic limit

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Anisotropic Plasticity of BN Nanotube

• Plastic collapse at 14.75 strain

(a)
(b)
(c)
(d)
(e)
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Anisotropic Plasticity of BN Nanotubes
Quantum Molecular Dynamics
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Comparison of Plastic Collapse of BN and C
Anisotropic strain release
Isotropic strain release
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BN Nanotubes - Nanomechanics

• BN nanotube based composite with anisotropic
  plasticity
• Nanostructured skin effect !

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Nanotube Electronics (Basics)
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Band Structure
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Nanoelectronics with Doping
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Nano Electromechanical Effects (NEMS)
Mechanical deformation alter the electronic
deformation Of nanotubes effect is chirality
dependent
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Mechano-Chemical Effects Kinky Chemistry
Cohesive Energy
Binding Energy
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Functionalization of Nanotubes
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Mechano-Chemical Effects Kinky chemistry
SEM images of MWNTs dispersed on a V-ridged
Formvar substrate
D. Srivastava, J. D. Schall, D. W. Brenner, K. D.
Ausman, M. Feng And R. Ruoff, J. Phys. Chem. Vol.
103, 4330 (1999).
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Molecular Machines and Laser Motor
J. Han, A Globus and R. Jaffe
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Molecular Machines and Laser Motor
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Computational Nanotechnology PSE
Nanomanipulation in Virtual World
Simulations
Experiments
Next Generation of Technology and Products
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Comments

• compressed C nanotube nanomechanics in
  composites
• BN nanotube is almost as stiff as a C nanotube
  with even higher
• elastic limit
• anisotropic plastic collapse is observed
• nanostructured skin effect
• functionality of a smart material
• concept of a mechanical kink catalyzed chemistry
  of flexible
• nanoscale materials
• kinky chemistry