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1 Mechanosynthesis Ralph C. Merkle Senior Fellow IMM.

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Presentation on theme: "1 Mechanosynthesis Ralph C. Merkle Senior Fellow IMM."— Presentation transcript:

1 1 Mechanosynthesis Ralph C. Merkle Senior Fellow IMM

2 2 (For further information, links to papers, links to other researchers) Long-term goal: design and ultimately build a diamondoid nanofactory. Web page

3 3 Health, wealth and atoms

4 4 Arranging atoms Flexibility Precision Cost

5 5 Richard Feynman,1959 There’s plenty of room at the bottom

6 6 PropertyDiamond’s valueComments Chemical reactivityExtremely low Hardness (kg/mm2)9000CBN: 4500 SiC: 4000 Thermal conductivity (W/cm-K)20Ag: 4.3 Cu: 4.0 Tensile strength (pascals)3.5 x 10 9 (natural)10 11 (theoretical) Compressive strength (pascals)10 11 (natural)5 x (theoretical) Band gap (ev)5.5Si: 1.1 GaAs: 1.4 Resistivity (W-cm)10 16 (natural) Density (gm/cm3)3.51 Thermal Expansion Coeff (K-1)0.8 x SiO2: 0.5 x Refractive 590 nmGlass: Coeff. of Friction0.05 (dry)Teflon: 0.05 Source: Crystallume Diamond physical properties What to make

7 7 Hydrocarbon bearing

8 8 Hydrocarbon universal joint

9 9 Rotary to linear NASA Ames

10 10 Bucky gears NASA Ames

11 11 Bearing

12 12 Planetary gear

13 13 Neon pump

14 14 Making diamond today Illustration courtesy of P1 Diamond Inc.

15 15 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

16 16 Positional assembly

17 17 σ:mean positional error k: restoring force k b : Boltzmann’s constant T:temperature Thermal noise

18 18 σ:0.02 nm (0.2 Å) k: 10 N/m k b : 1.38 x J/K T:300 K Thermal noise

19 19 Annotated bibliography on diamond mechanosynthesis Nanofactory/AnnBibDMS.htm Molecular tools (over 50 entries)

20 20 Hydrogen abstraction tool

21 21 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): 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): ; 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): 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): ; 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): 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): ; (abstract), (paper).http://pubs.acs.org/cgi-bin/abstract.cgi/jpcafh/2006/110/i38/abs/jp061821e.htmlhttp://www.MolecularAssembler.com/Papers/TemelsoHAbst.pdf Theoretical bibliography

22 22 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

23 23 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

24 24 New paper in preparation A Minimal Toolset for Positional Diamond Mechanosynthesis Robert A. Freitas Jr., Ralph C. Merkle Publication

25 25 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

26 26 Computational methods 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) Minimal toolset

27 27 Computational methods 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/ 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

28 28 Molecular tools HAbs HDon GM Germylene Methylene HTrans AdamRad DimerP GeRad

29 29 H donation Hydrogen donation onto a C(111) surface radical eV

30 30 H donation Hydrogen donation onto a C(110) surface radical eV

31 31 H donation Hydrogen donation onto a C(111) surface radical eV

32 32 H donation Recharging HAbs (initial approach of first GeRad optimized by Tarasov et al (2007), eV with -0.1 eV barrier) Second GeRad abstraction eV

33 33 C placement C placement on C(111) using GM tool C radical addition to C radical eV (note undesired H abstraction by C radical from sidewall, eV barrier) GeRad removal eV (note Ge-C bond is “soft”) HDon hydrogenate C radical eV

34 34 C placement 2 nd C placement on C on C(111) C radical addition to C radical eV (note undesired H abstraction by C radical from C radical, eV barrier) GeRad removal eV (note Ge-C bond is “soft”) HDon hydrogenate C radical eV

35 35 C placement C placement on C(100) using GM tool C radical addition to C radical eV (note undesired H abstraction by C radical from adjacent dimer, eV barrier) GeRad removal eV (note Ge-C bond is “soft”) HDon hydrogenate C radical eV

36 36 C placement C placement on adamantane when sidewall site is occupied

37 37 C placement C placement on adjacent site of C(111) surface

38 38 C placement 3 rd C placement on adjacent site of C(111) surface

39 39 C placement C placement on adjacent site of C(100) dimer

40 40 Making tools Building HAbs from DimerP

41 41 Making tools Building HAbs

42 42 Making GM tool

43 43 Making polyyne chain

44 44 Inputs/outputs 100% process closure 9 tools Feedstock: CH 4, C 2 H 2, Ge 2 H 6, and H 2 Flat depassivated diamond and germanium surfaces for C and Ge feedstock presentation Six(?) degree of freedom positional control

45 45 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)

46 46 Today Overview What we see when we look only at today’s experimental work

47 47 Core molecular manufacturing capabilities Today Products Overview The context that theory provides

48 48 Future work We will wander in the desert for a long time without the guidance that computational and theoretical work can provide

49 49 End of talk END OF TALK


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