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Science Forum Index » Nanotechnology Forum » Important new paper out from Freitas and Merkle
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| Perry E. Metzger |
 Posted: Tue Apr 22, 2008 11:32 am |
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Freitas and Merkle have just published a paper on nine "tooltips" for
mechanosynthesis that possess process closure -- that is, given all
nine, you can build all nine. They were designed with computational
chemistry simulations, rather than being synthesized and then tested,
so there is still a lot of work to do here before one can absolutely
know that the things work, but it is still an amazing achievement.
The paper is over 100 pages long, and required over 105,000 hours of
computer time to do the simulations.
From here, large amounts of work will be needed to validate the
designs with better simulations (i.e. "higher levels of theory" in
computational chemistry parlance) and to actually synthesize the
tooltips and get them attached to scanning microscopy probes.
See: http://www.aspbs.com/ctn/
A Minimal Toolset for Positional Diamond Mechanosynthesis
Freitas, Robert A.; Merkle, Ralph C.
Journal of Computational and Theoretical Nanoscience, Volume
5, Number 5, May 2008 , pp. 760-861(102)
DOI: 10.1166/jctn.2008.002
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 ( 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.
Perry |
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| Tim Tyler |
| Posted: Tue Apr 22, 2008 9:20 pm |
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Perry E. Metzger wrote:
Quote: See: http://www.aspbs.com/ctn/
A Minimal Toolset for Positional Diamond Mechanosynthesis
Freitas, Robert A.; Merkle, Ralph C.
Journal of Computational and Theoretical Nanoscience, Volume
5, Number 5, May 2008 , pp. 760-861(102)
DOI: 10.1166/jctn.2008.002 [...]
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.
Although none of this has actually been tested 
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| James A. Donald |
| Posted: Fri Apr 25, 2008 11:43 am |
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On Tue, 22 Apr 2008 21:20:27 -0500, Tim Tyler
<seemysig@googlemail.com> wrote:
Quote:
Perry E. Metzger wrote:
See: http://www.aspbs.com/ctn/
A Minimal Toolset for Positional Diamond Mechanosynthesis
Freitas, Robert A.; Merkle, Ralph C.
Journal of Computational and Theoretical Nanoscience, Volume
5, Number 5, May 2008 , pp. 760-861(102)
DOI: 10.1166/jctn.2008.002 [...]
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.
Although none of this has actually been tested
And assuming it can be tested, does not mean we can build the first
one.
The great ingenuity of the first lathe was that it could be built by a
blacksmith - in fact, everything about the first lathe could be made
by black smith, a woodcarver, and a stonecutter, starting from
charcoal, iron ore and stones, and probably was so made. Figuring out
how to build a lathe, assuming you already have a lathe, is easy.
Building the first lathe from primitive materials and simple tools of
hammered and ground iron made from primitive materials was the hard
part.
Back then, a blacksmith would often himself toss lumps of iron ore in
the fire, where they would convert iron sponge, and then himself
hammer the iron sponge into useful things - and eventually one of
these useful things was a bizarrely modern lathe capable of
constructing precision instruments. We have reconstruction of how it
was done, starting with primitive materials.
--
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We have the right to defend ourselves and our property, because
of the kind of animals that we are. True law derives from this
right, not from the arbitrary power of the omnipotent state.
http://www.jim.com/ James A. Donald |
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| James A. Donald |
| Posted: Fri Apr 25, 2008 11:43 am |
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On Tue, 22 Apr 2008 11:32:09 -0500, "Perry E. Metzger"
<perry@piermont.com> wrote:
Quote:
Freitas and Merkle have just published a paper on nine "tooltips" for
mechanosynthesis that possess process closure -- that is, given all
nine, you can build all nine. They were designed with computational
chemistry simulations, rather than being synthesized and then tested,
so there is still a lot of work to do here before one can absolutely
know that the things work, but it is still an amazing achievement.
The paper is over 100 pages long, and required over 105,000 hours of
computer time to do the simulations.
From here, large amounts of work will be needed to validate the
designs with better simulations (i.e. "higher levels of theory" in
computational chemistry parlance) and to actually synthesize the
tooltips and get them attached to scanning microscopy probes.
This simulation is important, in that it shows, to the extent that a
simulation can, that Drexlerian mechanosynthesis (done in cold vacuum)
is possible, something I was much inclined to doubt.
The mechanosynthesis reactions proposed require quite large forces and
quite fine precision. Are there any estimates on the properties
required for the scanning microscopy probes?
I suspect that for our first practical mechanosynthesis device, we
might need more forgiving tooltips.
--
----------------------
We have the right to defend ourselves and our property, because
of the kind of animals that we are. True law derives from this
right, not from the arbitrary power of the omnipotent state.
http://www.jim.com/ James A. Donald |
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| Tim Tyler |
| Posted: Mon Apr 28, 2008 11:28 am |
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Perry E. Metzger wrote:
Quote: Actual nanomachines will be the most complicated objects ever produced
by man. One should not assume that the path to building such things
will be cheap and easy. It takes gargantuan sums of money and armies
of people working very hard to design a new microprocessor, so
we should expect something far more complicated to have higher
barriers, if anything.
What about the cost of the product? Say, hypothetically, that it is
possible to pull those H atoms off and replace them by carbon atoms
pulled from a C source - and form a large lattice, one atom at a
time, using a pointy tool, and get a low error rate at 80 K. That's
a number of mechanically-broken bonds per atom, and the acceleration
and deceleration expenditure on the tool and its holder - probably
plus a whole bunch of monitoring costs, so the constructor can see
what it is doing when grabbing carbon atoms.
Has anyone ever calculated how much it would cost (in terms of
energy costs) to make a diamond that way? How would it compare to:
http://en.wikipedia.org/wiki/Chemical_vapor_deposition_of_diamond
....? Rather poorly, I would expect.
This seems like a kind of "brute force" nanotechnology to me.
It doesn't follow the Taoist principle of cooperating with nature.
They won't make diamonds - but I would expect fields such as DNA
self-assembly to make much better progress than this sort of thing.
--
__________
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