Mechanosynthesis

1
Mechanosynthesis

• Ralph C. Merkle
• Senior Fellow IMM

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Web page

• www.molecularassembler.com/Nanofactory/
• (For further information, links to papers, links
  to other researchers)
• Long-term goal design and ultimately build a
  diamondoid nanofactory.

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Health, wealth and atoms
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Arranging atoms

• Flexibility
• Precision
• Cost

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Richard Feynman,1959
Theres plenty of room at the bottom
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What to make
Diamond physical properties

• Property Diamonds value Comments
• Chemical reactivity Extremely low
• Hardness (kg/mm2) 9000 CBN 4500 SiC 4000
• Thermal conductivity (W/cm-K) 20 Ag 4.3 Cu
  4.0
• Tensile strength (pascals) 3.5 x 109
  (natural) 1011 (theoretical)
• Compressive strength (pascals) 1011 (natural) 5 x
  1011 (theoretical)
• Band gap (ev) 5.5 Si 1.1 GaAs 1.4
• Resistivity (W-cm) 1016 (natural)
• Density (gm/cm3) 3.51
• Thermal Expansion Coeff (K-1) 0.8 x 10-6 SiO2
  0.5 x 10-6
• Refractive index 2.41 _at_ 590 nm Glass 1.4 - 1.8
• Coeff. of Friction 0.05 (dry) Teflon 0.05
• Source Crystallume

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Hydrocarbon bearing
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Hydrocarbon universal joint
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Rotary to linear
NASA Ames
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Bucky gears
NASA Ames
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Bearing
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Planetary gear
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Neon pump
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Making diamond today
Illustration courtesy of P1 Diamond Inc.
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A synthetic strategy for the synthesis of
diamondoid structures
Molecular tools

• Positional assembly (6 degrees of freedom)
• Highly reactive compounds (radicals, carbenes,
  etc)
• Inert environment (vacuum, noble gas) to
  eliminate side reactions

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Positional assembly
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Thermal noise
s mean positional error k restoring force kb
Boltzmanns constant T temperature
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Thermal noise
s 0.02 nm (0.2 Å) k 10 N/m kb 1.38 x 10-23
J/K T 300 K
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Annotated bibliography on diamond mechanosynthesis
Molecular tools
(over 50 entries)

• http//www.molecularassembler.com/
• Nanofactory/AnnBibDMS.htm

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Hydrogen abstraction tool
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Hydrogen abstraction tools
Theoretical bibliography

• Michael Page, Donald W. Brenner, Hydrogen
  abstraction from a diamond surface Ab initio
  quantum chemical study using constrained
  isobutane as a model, J. Am. Chem. Soc.
  113(1991)3270-3274.
• Charles B. Musgrave, Jason K. Perry, Ralph C.
  Merkle, William A. Goddard III, Theoretical
  studies of a hydrogen abstraction tool for
  nanotechnology, Nanotechnology 2(1991)187-195
  http//www.zyvex.com/nanotech/Habs/Habs.html
• Xiao Yan Chang, Martin Perry, James Peploski,
  Donald L. Thompson, Lionel M. Raff, Theoretical
  studies of hydrogen-abstraction reactions from
  diamond and diamond-like surfaces, J. Chem.
  Phys. 99(15 September 1993)4748-4758.
• Susan B. Sinnott, Richard J. Colton, Carter T.
  White, Donald W. Brenner, Surface patterning by
  atomically-controlled chemical forces molecular
  dynamics simulations, Surf. Sci.
  316(1994)L1055-L1060.
• D.W. Brenner, S.B. Sinnott, J.A. Harrison, O.A.
  Shenderova, Simulated engineering of
  nanostructures, Nanotechnology 7(1996)161-167
  http//www.zyvex.com/nanotech/nano4/brennerPaper.p
  df
• A. Ricca, C.W. Bauschlicher Jr., J.K. Kang, C.B.
  Musgrave, Hydrogen abstraction from a diamond
  (111) surface in a uniform electric field, Surf.
  Sci. 429(1999)199-205.
• Berhane Temelso, C. David Sherrill, Ralph C.
  Merkle, Robert A. Freitas Jr., High-level Ab
  Initio Studies of Hydrogen Abstraction from
  Prototype Hydrocarbon Systems, J. Phys. Chem. A
  110(28 September 2006)11160-11173
  http//pubs.acs.org/cgi-bin/abstract.cgi/jpcafh/20
  06/110/i38/abs/jp061821e.html (abstract),
  http//www.MolecularAssembler.com/Papers/TemelsoHA
  bst.pdf (paper).

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Dimer placement
Fig. 2. Stepwise retraction simulation of
Ge-based tool from clean diamond C(110) surface
(A) initial configuration (C in brown, H in
white, Ge in blue) (B) ending configuration
after 200 fs at 1.6 Å above starting position, at
300 K. Peng et al., work done at Zyvex using VASP
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High complexity
Making almost anything

• Over 100 elements in periodic table
• Therefore over 100 tools
• Combinatorial explosion in considering reaction
  sequences
• Can build almost any structure consistent with
  physical law
• Great flexibility in synthesis

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New paper in preparation
Publication

• A Minimal Toolset for Positional Diamond
  Mechanosynthesis
• Robert A. Freitas Jr., Ralph C. Merkle

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Three elements H, C, Ge
Reduce complexity

• Limit combinatorial explosion
• H and C can build almost any rigid structure
  (diamond, lonsdaleite, graphite, buckytubes,
  fullerenes, carbyne, organic compounds)
• Ge provides just enough synthetic flexibility

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Computational methods
Minimal toolset

• 1630 tooltip/workpiece structures
• 65 Reaction Sequences
• 328 reaction steps
• 354 unique pathological side reactions
• 1321 reported energies
• consuming 102,188 CPU-hours (using 1-GHz CPUs)

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Computational methods
Minimal toolset

• Gaussian 98
• Singlet or doublet geometries optimized with no
  constrained degrees of freedom using
  spin-unrestricted Hartree-Fock (UHF) analysis at
  the B3LYP/3-21G level of theory
• Single point energy calculations performed at the
  B3LYP/6-311G(2d,p) level of theory
• The mean absolute deviation from experiment (MAD)
  for B3LYP/6-311G(2d,p) // B3LYP/3-21G energies
  is estimated as 0.14 eV for carbon-rich molecules
• Barriers of 0.4 eV against side reactions in most
  cases

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Molecular tools
HAbs HDon GM Germylene
Methylene
HTrans AdamRad DimerP GeRad
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H donation
Hydrogen donation onto a C(111) surface
radical. -0.61 eV
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H donation


Hydrogen donation onto a C(110) surface
radical. -0.73 eV

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H donation


Hydrogen donation onto a C(111) surface
radical. -1.43 eV

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H donation



Recharging HAbs (initial approach of first GeRad
optimized by Tarasov et al (2007), -0.43 eV with
-0.1 eV barrier) Second GeRad abstraction -0.83
eV






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C placement




C placement on C(111) using GM tool C radical
addition to C radical -3.17 eV (note undesired H
abstraction by C radical from sidewall, 0.63 eV
barrier) GeRad removal 2.76 eV (note Ge-C bond
is soft) HDon hydrogenate C radical -0.70 eV










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C placement
2nd C placement on C on C(111) C radical addition
to C radical -3.12 eV (note undesired H
abstraction by C radical from C radical, 0.69 eV
barrier) GeRad removal 2.74 eV (note Ge-C bond
is soft) HDon hydrogenate C radical -0.65 eV

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C placement




C placement on C(100) using GM tool C radical
addition to C radical -3.29 eV (note undesired H
abstraction by C radical from adjacent dimer,
0.55 eV barrier) GeRad removal 2.66 eV (note
Ge-C bond is soft) HDon hydrogenate C radical
-0.64 eV










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C placement





C placement on adamantane when sidewall site is
occupied













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C placement





C placement on adjacent site of C(111) surface













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C placement
3rd C placement on adjacent site of C(111) surface


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C placement







C placement on adjacent site of C(100) dimer
















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Making tools
Building HAbs from DimerP



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Making tools
Building HAbs

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Making GM tool




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Making polyyne chain



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Inputs/outputs

• 100 process closure
• 9 tools
• Feedstock CH4, C2H2, Ge2H6, and H2
• Flat depassivated diamond and germanium surfaces
  for C and Ge feedstock presentation
• Six(?) degree of freedom positional control

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Future work

• Further analysis of all reactions (higher level
  of theory, molecular dynamics, etc)
• Note the volume of work for HAbs alone analysis
  of all reactions at this depth will require
  substantial resources
• Development of directly accessible experimental
  pathways (the Direct Path)

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Overview
What we see when we look only at todays
experimental work
Today
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Overview
Core molecular manufacturing capabilities
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Today
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The context that theory provides
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Future work
We will wander in the desert for a long time
without the guidance that computational and
theoretical work can provide



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End of talk


END OF TALK