NASA Sponsored Computational Nanotechnology Project:

Principal Investigators

Accomplishments

The following list includes the projects completed, papers submitted, preprints (including the links which has the detailed materials on the progress over the 1997 funding year) and educational impact and public outreach aspects of the NASA sponsored Computational Nanotechnology Project.

1. Molecular Mechanics and Molecular Dynamics Studies of alkali doped Single Walled Nanotubes [1]

2. Characterization of SWNTs and Tori with accurate (QM derived) Force Fields using molecular mechanics [2]

3. Molecular Dynamics and Molecular Mechanics Simulations of Nanomachines [3]

4. Extensive Quantum Mechanical (QM) studies of diamond mechano-synthesis [4]

5. Development of Nanodevice and Nanomachine Simulation Tools in a Molecular Modeling Environment[5]

6. Incorporation and extension of Empirical Bond Order Dependent Potentials for Carbon Nanotechnology into MPSim, and Polygraf[6]

7. Substantial portion of the thesis of Dr. Guanghua Gao focused on the carbon based computational nanotechnology[7]

8. A visiting scientist is trained in computational nanotechnology applications and will complete his Ph.D. in the area of connection between robotics and molecular nanotechnology.[8]

9. A postdoctoral scholar is being trained in the areas of computational nanotechnology and nanotribology.[9]

10. Senior Investigators have presented research results in the computational nanotechnology project at various conferences.

Ongoing Projects

1. Empirical Bond Order Dependent Potentials: Development of EBOP with terms to represent long range tube-tube interactions in a continuous manner to address nano and micro tribology problems for nano-mechanical and micro mechanical devices. The problems of wear and friction are especially important in the design of nano- or micro-mechanical devices for long term space mission. The preliminary results of this investigation will be presented at the American Physical Society March 1998 meeting.[10]
2. Molecular Self Assembly: Researchers at the MSC have made substantial progress in investigating the role molecular self assembly of Langmuir Blodgett (LB) films on Gold[11], of corrosion inhibitors[12] and of wear inhibitors[13] on metals and ceramics. At present, we are investigating the tribology of molecularly thin self assembled layers and their influence on device operations. These systems involve heteregenous systems composed of surfaces (mostly hard materials), physisorbed or chemisorbed organic molecularly thin layers on these surfaces and fluid interfaces. Preliminary results of this initiative will be presented at the upcoming American Physical Society March 1998 meeting and ACS 1998 August meetings.[14]
3. Supramolecular Assembly: The convergent and divergent synthetic methods developed for dendrimers have substantial potential in the design of tailored hyperbranched structures for use in molecular nanotechnology applications. We have initiated a subproject to understand the self assembly of dendrimers on surfaces as possible nano- or micro scale sensor applications.[15]
4. Transport Properties of Carbon Nanotubes: Nanotubes as nano electronic device components are being experimented by many researchers at various labs. In nanoelectronic devices, one of the issues that needs to be studied is the thermal transport properties of the carbon nanotubes. At the MSC over the past two years Cagin and Goddard have developed non equilibrium molecular dynamics techniques to study the transport properties of materials by employing synthetic fields to generate currents and measure the response of materials. Until recently, most of the applications have centered around mass transport and flow properties[16] such as diffusion constants[17] and viscosity index for fluids.[16] Recently we have focused on the thermal transport using a synthetic hamiltonian approach. Over the next year we plan to study the thermal conductivity of nanotubes using the NEMD techniques.
5. Modeling and Simulation tools for Computational Nanotechnology: We will continue to develop tools for molecular nanotechnology in MPSim and SDK.

New Projects

1. Inherent Tribological Properties of Nanoscale Materials At present, silicon forms the basis of microelectronic and microelectromechanical devices. However, silicon has inherently less desirable wear properties when compared to diamond and polycrystalline diamond. The promising developments in carbon nanotube synthesis and application make carbon based materials attractive for device design. Using advanced quantum mechanical techniques, we will investigate the wear phenomena at the electronic level.
2. Failure Mechanisms in Nanotubes:Using steady state molecular dynamics techniques and long range corrected EBOPs, we plan to investigate the yield, fracture and failure of nanotubes as a function of strain rate and strain profiles. The steady state molecular dynamics technique differs from standard equilibrium molecular dynamics techniques in the sense that the the system is not at equilibrium, but it is maintained under a steady state by the presence of various thermodynamic baths. The thermodynamic baths include heat, pressure and stress for which a constant gradient is maintained.

Personnel and Collaborators

Citations

1. G. Gao, T. Cagin, and W. A. Goddard, III "Where the K are in doped single walled carbon nanotube crystals," submitted for publications and results presented at the Fifth Foresight Conference on Nanotechnology, Palo Alto, Nov. 7, 1997.
2. G. Gao, T. Cagin, and W. A. Goddard, III. "Structure, thermodynamic and mechanical properties of nanotubes," presented at the Fifth Foresight Conference on Nanotechnology, Palo Alto, Nov. 7, 1997; "Energetics, Structure, Mechanical and Vibrational Properties of Carbon Nanotubes and Nanofibers" to be submitted.
3. T. Cagin, A. Jaramillo-Botero, G. Gao, and W. A. Goddard, III "Molecular Mechanics and Molecular Dynamics Analysis of Drexler-Merkle Gears and Neon Pump", presented presented at the Fifth Foresight Conference on Nanotechnology, Palo Alto, Nov. 7, 1997.
4. S.P. Walch, W.A. Goddard, III, and R.M. Merkle "Theoretical studies of reactions on diamond surfaces", presented at the Fifth Foresight Conference on Nanotechnology, Palo Alto, Nov. 7, 1997.
5. J.W. Che, G. Gao, T. Cagin, W. A. Goddard, III, "Comparative studies on Properties of Carbon Nano tubes and Nano tori", in progress. This work compares the standard EBOP of Brenner, modified Brenner (with a long range correction) and Quantum Mechanics Derived Force Fields developed at the MSC.
6. The program is developed in Cerius² using Software Developers Kit (SDK) utilizes equilibrium and nonequilibrium Molecular Dynamics Techniques and manipulating capabilities most suitable for designing nanoscale molecular machines and devices. It is currently being reviewed and revised by us to expand the specifications based on suggestions from the Modellers.
7. Guanghua Gao, Ph. D. Thesis, California Institute of Technology, 1997.
8. Andres Jaramillo-Botero. Electronic Engineering Program Director. Engineering Faculty, PONTIFICIA UNIVERSIDAD JAVERIANA, Cali, Colombia.
9. Dr. Jianwei Che.
10. J. W. Che, T. Cagin, W. A. Goddard, III, in progress.
11. C. F. Fan, J. Gerdy, W. A. Goddard, III, submitted.
12. S. Ramachandran, B-L. Tsai, M. Blanco, H. Chen, Y. Tang, and W. A. Goddard III, "Self-Assembled Monolayer Mechanism for Corrosion Inhibition of Iron by Imidazolines", Langmuir 121, 6419 (1996)
13. S. Jiang, R. Frazier, E. S. Yamaguchi, M. Blanco, S. Dasgupta, Y. Zhou, T. Cagin, Y. Tang, and W. A. Goddard III "The SAM Model for Wear Inhibitor Performance of Dithiophosphates on Iron Oxide" J. Phys. Chem. B 101, 7702 (1997)
14. Y. H. Zhuo, T. Cagin, W. A. Goddard, III, in progress.
15. P. Miklis, T. Cagin, and W. A. Goddard III "Dynamics of Bengal Rose Encapsulated in the Meijer Dendrimer Box" J. Am. Chem. Soc. 119, 7458 (1997)
16. Yue Qi, T. Cagin. Y. Kimura, W. A. Goddard III, "Shear Viscosity of a Liquid Metal Alloy from NEMD: Au-Cu", submitted.
17. M. Iotov, S. Keshiara, S. D. Dasgupta, W. A. Goddard, III, "Diffusion of Gases in Polymers", to be submitted; M. Iotov, Ph. D. Thesis, California Institute of Technology, December 1997.