[tt] A Minimal Toolset for Positional Diamond Mechanosynthesis

[Brian Atkins]

http://www.ingentaconnect.com/content/asp/jctn/2008/00000005/00000005/art00002

A Minimal Toolset for Positional Diamond Mechanosynthesis

Authors: Freitas, Robert A.; Merkle, Ralph C.

Source: Journal of Computational and Theoretical Nanoscience, Volume 5, Number 
5, May 2008 , pp. 760-861(102)

Abstract:

This paper presents the first theoretical quantitative systems level study of a 
complete suite of reaction pathways for scanning-probe based ultrahigh-vacuum 
diamond mechanosynthesis (DMS). A minimal toolset is proposed for positionally 
controlled DMS consisting of three primary tools—the (1) Hydrogen Abstraction 
(HAbst), (2) Hydrogen Donation (HDon), and (3) Dimer Placement (DimerP) 
tools—and six auxiliary tools—the (4) Adamantane radical (AdamRad) and (5) 
Germyladamantane radical (GeRad) handles, the (6) Methylene (Meth), (7) 
Germylmethylene (GM), and (8) Germylene (Germ) tools, and (9) the Hydrogen 
Transfer (HTrans) tool which is a simple compound of two existing tools (HAbst + 
GeRad). Our description of this toolset, the first to exhibit 100% process 
closure, explicitly specifies all reaction steps and reaction pathologies, also 
for the first time. The toolset employs three element types (C, Ge, and H) and 
requires inputs of four feedstock molecules—CH4 and C2H2 as carbon sources, 
Ge2H6 as the germanium source, and H2 as a hydrogen source. The present work 
shows that the 9-tooltype toolset can, using only these simple bulk-produced 
chemical inputs: (1) fabricate all nine tooltypes, including their adamantane 
handle structures and reactive tool intermediates, starting from a flat 
passivated diamond surface or an adamantane seed structure; (2) recharge all 
nine tooltypes after use; and (3) build both clean and hydrogenated 
molecularly-precise unstrained cubic diamond C(111)/C(110)/C(100) and hexagonal 
diamond surfaces of process-unlimited size, including some Ge-substituted 
variants; methylated and ethylated surface structures; handled polyyne, 
polyacetylene and polyethylene chains of process-unlimited length; and both flat 
graphene sheet and curved graphene nanotubes. Reaction pathways and transition 
geometries involving 1620 tooltip/workpiece structures were analyzed using 
Density Functional Theory (DFT) in Gaussian 98 at the B3LYP/6-311+G(2d,p) // 
B3LYP/3-21G* level of theory to compile 65 Reaction Sequences comprised of 328 
reaction steps, 354 unique pathological side reactions and 1321 reported DFT 
energies. The reactions should exhibit high reliability at 80 K and moderate 
reliability at 300 K. This toolset provides clear developmental targets for a 
comprehensive near-term DMS implementation program.
-- 
Brian Atkins
Singularity Institute for Artificial Intelligence
http://www.singinst.org/