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Theoretical studies of reactions on diamond surfaces

S.P. Walch*(a), W.A. Goddard, III(b), and R.M. Merkle(c)

(a)Thermosciences Institute (MS 230-3)
NASA Ames Research Center
Moffett Field, CA 94035-1000
(b)Materials and Process Simulation Center
Beckman Institute
California Institute of Technology
Pasadena, CA 91125
(c)Xerox, PARC
3333 Coyote Hill Road
Palo Alto, CA 94304
This is an abstract for a talk to be given at the Fifth Foresight Conference on Molecular Nanotechnology. The full article is available at the author's web site.
Density functional theory and other methods are being used to examine reactions of tools and other molecules with diamond surfaces.

In one study, we looked at the interaction of several mechanosynthesis tools with a pair of radical sites on the diamond (111) surface. The carbene tool (carbenecyclopropene) is found to bond preferentially to a single radical site (on top site) rather than at a bridged site. This means this tool is not useful for adding a carbon to diamond (111). The C2 tool, on the other hand, is found to add a bridged C2 molecule, through a series of steps which are overall exothermic. The carbene tool can add a carbon to the bridged C2 molecule, leading to a bridged C3 molecule perpendicular to the surface, by an overall exothermic series of steps. If another radical site is activated, the C3 can bend over to a three fold coordinated position, with only a small barrier. Thus, this series of steps can be used to create a three fold coordinated C3 molecule on the diamond (111) surface. These studies are being extended to the reconstructed diamond (100) surface.

In another study, we are looking at the reaction of H and H2 with the reconstructed diamond(100) surface. We are interested in barriers to addition, abstraction, and migration.

Finally, we are planning studies (which should be complete by the time of the meeting) of the reaction of acetylene with the reconstructed diamond (100) surface.

*Corresponding Address:
Stephen P. Walch, Thermosciences Institute (MS 230-3), NASA Ames Research Center, Moffett Field, CA 94035-1000, ph: 415-604-6189, fax: 415-604-0350, email: walch@pegasus.arc.nasa.gov
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