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Mechanosynthesis

Ralph C. MerkleSenior Fellow IMM

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www.molecularassembler.com/Nanofactory/(For further information, links to papers, links to other researchers)

Long-term goal: design and ultimately build a diamondoid nanofactory.

Web page

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Health, wealth and atoms

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Arranging atoms

• Flexibility• Precision• Cost

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Richard Feynman,1959

There’s plenty of roomat the bottom

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Property Diamond’s value Comments

Chemical reactivity Extremely lowHardness (kg/mm2) 9000 CBN: 4500 SiC: 4000Thermal conductivity (W/cm-K) 20 Ag: 4.3 Cu: 4.0Tensile 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: 1.4Resistivity (W-cm) 1016 (natural)Density (gm/cm3) 3.51Thermal Expansion Coeff (K-1) 0.8 x 10-6 SiO2: 0.5 x 10-6

Refractive index 2.41 @ 590 nm Glass: 1.4 - 1.8Coeff. of Friction 0.05 (dry) Teflon: 0.05

Source: Crystallume

Diamond physical properties

What to make

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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

• Positional assembly (6 degrees of freedom)• Highly reactive compounds (radicals,

carbenes, etc)• Inert environment (vacuum, noble gas) to

eliminate side reactions

Molecular tools

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Positional assembly

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kTkb2

σ: mean positional error k: restoring forcekb: Boltzmann’s constantT: temperature

Thermal noise

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kTkb2

σ: 0.02 nm (0.2 Å) k: 10 N/mkb: 1.38 x 10-23 J/KT: 300 K

Thermal noise

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Annotated bibliography on diamond mechanosynthesis

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

Molecular tools

(over 50 entries)

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Hydrogen abstraction tool

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Hydrogen abstraction tools

•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.pdf•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/2006/110/i38/abs/jp061821e.html (abstract), http://www.MolecularAssembler.com/Papers/TemelsoHAbst.pdf (paper).

Theoretical bibliography

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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

• 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

Making almost anything

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New paper in preparation

• A Minimal Toolset for Positional Diamond Mechanosynthesis

• Robert A. Freitas Jr., Ralph C. Merkle

Publication

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Three elements: H, C, Ge

• 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

Reduce complexity

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Computational methods

1630 tooltip/workpiece structures65 Reaction Sequences328 reaction steps354 unique pathological side reactions1321 reported energiesconsuming 102,188 CPU-hours (using 1-GHz

CPUs)

Minimal toolset

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Computational methodsGaussian 98Singlet 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/6-311+G(2d,p) level of theory

The mean absolute deviation from experiment (MAD) for B3LYP/6-311+G(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

Minimal toolset

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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 toolC 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 toolC 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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Today

Overview

What we see when we look only at today’s experimental work

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Core molecularmanufacturingcapabilities

Today

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Overview

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