NSF Pan-American Advanced Studies Institutes (PASI) Workshop January 5-16, 2004

1. NSF Pan-American Advanced Studies Institutes (PASI) WorkshopJanuary 5-16, 2004 Computational Nanotechnology and Molecular Engineering MSC/Caltech: Dr. Mario Blanco and Dr. Mamadou Diallo First principles Simulations of Nanoscale Materials Technology William A. Goddard III Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics Director, Materials and Process Simulation Center California Institute of Technology, Pasadena, California 91125 [http://www.wag.caltech.edu]

2. Who is Goddard? Born El Centro, California (in Southern California deserteast San Diego) Public schools of El Centro, Delano, Indio, Lodi, Firebaugh, MacFarland, Oildale (Bakersfield), Modesto, Yuma BS Engineering, UCLA,June, 1960 PhD Engineering Science (Minor physics) CaltechOct. 1964 Caltech Chemistry FacultyNov. 1964-2024 108 PhD’s, 550 publications, Member National Academy of Science, Int. Acad. Quantum Molec. Sci. 8 patents in protein structure prediction, new polymerization catalysts, semiconducting processing modeling Co-founded 5 companies(all still thriving) William Goddard PhD (Engr. Sci. 1965,Caltech) advisor: Pol Duwez Pol Duwez DSc (1933, Brussels) advisor: Emile Henriot Emile Henriot DSc (Phys, 1912, Sorbonne, Paris) advisor: Marie Curie Marie Curie DSc (1903, Ecole Phys. Chim. Ind, Paris) advisor: Becqeurel

3. What is Caltech? Throop University founded in 1891 (at Green and Fair Oaks, near old town Pasadena). vocational college, high school, grammar school ~1905George Ellery Hale, Astronomer came to Pasadena to build Mt. Wilson Observatory (because of clear air) In ~ 1907 changed from to Throop Polytechnic Institute (engineering college) In ~1910 Throop moved to current site (previously a citrus grove) ~1915Arthur Amos Noyes came from MIT to start science (chemistry) at Caltech ~1918 Noyes attracted Robert A. Millikan to Caltech In ~ 1920 changed to California Institute of Technology In 1920’s Nobel Prizes to Mulliken (Physics), Morgan (Biology)

4. Caltech Today • Six Divisions: • Chemistry and Chemical Engineering • Biology • Geosciences • Physics, Math, and Astronomy • Engineering and Applied Science • Humanities and Social Science • ~1000 undergraduates • ~1200 graduate students • ~350 faculty

5. What is Beckman Institute? • Gift by Arnold and Mabel Beckman • (Arnold got PhD at Caltech, stayed of faculty for 10 years, then started Beckman Instruments) • Construction finished July,1990 • Resource Centers in Chemistry and Biology • Imaging • Lasers • Materials • Synthesis • Materials and Process Simulation Center (MSC)

6. What is Materials and Process Simulation Center? (MSC) Senior Staff: All involved in nanotechnolgy William A. Goddard III, Director Blanco, Director Process Simulations and Industrial Technology Cagin, Director Mesoscale and Materials Science Technology van Duin, Director Force Field and Materials Technology Vaidehi, Director of Biotechnology and Pharma Meulbroek, Director Software Integration and Databases Oxgaard, Director of Quantum and CatalysisTechnology Diallo, Manager Molecular Environmental Technology Molinero, Manager of Complex Materials Simulations Willick, Manager of Computer Technology and Networks Staff: (over 60)Trained in Chem., Phys., Mat. Sci., Appl. Phys., Biol., Envir. Engr., Chem. Eng., Comp. Sci., Elect. Engr. Excellent team for complex problems Critical Mass of Expertise in Most areas of Atomistic Theory and Applications to Materials, Chemistry, and Biology Including QM, FF, MD, MesoDyn, Stat. Mech. Biochem., Catalysis, Ceramics, Polymers, Semicond., Metal Alloys, Nanotechnology, Environmental Technology

7. Vision of MSC: First Principles Modeling: Base on QMTo predict macroscale from QM use Multiscale Strategy ELECTRONS ATOMS GRAINS GRIDS time hours Continuum (FEM) Fracture, Plasticity, Creep, Fatigue with application scales of time-space seconds Build from QMFFMDMesoContinuum MESO microsec nanosec MD picosec FF Constitutive relations mechanisms plastic deformation Mesoscale FF (beads) MD simulations of deformation QM EOS of different phases, vacancy energy, surface energy femtosec distance Å nm micron mm meters First principles Force Field

8. Materials and Process Simulation Center (MSC) Each student involved with both • developing tools (theory and software) to solve impossible problems (1/2 effort) • using simulation (and experiment) to develop new materials and processes materials (1/2 effort) • Nearly every project has a strong coupling with experiment • Experiment stimulates current theory with impossible problems • Results from simulation guide and interpret experiments • Experiment essential to validate theory and simulation • Ultimately, de novo simulation will be at the heart of chemistry, biology, materials science

9. Theory Essential to solve Grand Challenges in Technology Materials Science: Nanoscale Technology • Opportunity: Tremendous potential for new functional materials (artificial machines smaller than cells) • Problems: Synthesis, Characterization, Design • Need Multiscale Modeling: couple time/length scales from electrons/atoms to manufacturing Biology: Protein Folding: Predict all structures of life • Opportunity Will soon have Genomes for All Life Now: Over 700,000 genes but only ~10,000 protein structures • Problem: experiment can do only ~ 2000/year ($200 million) • Need: Prediction of Reliable Protein Structure and Function for 1,000,000 proteins Chemistry: Methane (CH4) Activation, Gas to Liquid • Opportunity Enormous reserves of CH4 for energy, chemicals, and materials, mostly wasted • Problem: no efficient, selective, low temperature catalyst • Need: Predictive Mechanism to predict new catalysts First Principles Theory will lead developments of new technologies in 21st Century

10. Applications Focus at the MSC • BIOTECHNOLGY: MembraneProteins (GPCR), non-natural Amino Acids, Pharma (VLS) • POLYMERS: PEM (nafion),Dendrimers, Gas diffusion, Surface Tension, Biobased • CATALYSTS: Methane Activation, Selective Oxidation, ElectroCat (O2), Polar Olefins • SEMICONDUCTORS: Dielectric Breakdown,Si/SiO2/Si3N4 interfaces,B diffusion • CERAMICS: Ferroelectrics,Zeolites, Exfoliation Clays • METAL ALLOYS:Glass Formation,Plasticity (dislocations, crack propagation, spall) • NANOSYSTEMS: DNA based Machines,Carbon Nanotubes, nanoelectronics • ENVIRONMENTAL: Dendrimers for Selective Encapsulation, Humic acid • INDUSTRIAL APPLICATIONS(GM-GAPC, ChevronTexaco, GM-R&D, Asahi Kasei, Toray) • Polymers: Gas Diffusion, Surface Tension Modification, Water solubility • Polymerization Catalysts for Polar Monomers • Catalysts: CH4 activation, Alkylation phenols, zeolites (Acid sites/templates) • Semiconductors: Dielectric Breakdown nanometer oxides, nitrides, B Diffusion in Si • Automobile Engines: Wear Inhibitors (iron and aluminum based engines) • Oil Pipelines: Inhibitors for Corrosion , Scale, Wax; Hydrates, Demulsifiers • Oil Fields: Surfactants for low water/oil interface energy, Basin models • Ceramics: Bragg Reflection Gratings • Catalysts: ammoxidation of propane • Fuel Cells: H2 Storage, Polymer Electrolyte Membranes, Electrocatalysis

11. Stimulation toward solving impossible problemsCollaborations with Industry • GM advanced propulsion: Fuel Cells (store H2, membrane, cathode) • Chevron Corporation: CH4 to CH3OH, Alkylation, Wax Inhibition • General Motors - Wear inhibition in Aluminum engines • Seiko-Epson: Dielectric Breakdown in nm oxide films, TED(B/Si) • Asahi Kasei: AmmoxidationCatalysis, polymer properties • Berlex Biopharma: Structures and Function of CCR1 and CCR5 (GPCRs) • Aventis Pharma:Structures and Function of GPCR’s Asahi Glass: Fluorinated Polymers and Ceramics Avery-Dennison: Nanocomposites for computer screensAdhesives, Catalysis BP Amoco: HeterogeneousCatalysis (alkanes to chemicals, EO) Dow Chemical: Microstructure copolymers, Catalysis polymerize polar olefins Exxon Corporation:Catalysis (Reforming to obtain High cetane diesel fuel) Hughes Satellites/Raytheon: Carbon Based MEMS Hughes Research Labs: Hg Compounds for HgCdTe from MOMBE Kellogg:Carbohydrates/sugars(corn flakes)Structures, water content MMM: Surface Tension and structure of polymers Nippon Steel: CO + H2 to CH3OH over metal catalysts Owens-Corning: Fiberglas (coupling of matrix to fiber) Saudi Aramco: Demulsifiers, Asphaltenes Each project (3 Years) supports full time postdoc and part of a senior scientist

12. Quantum Mechanics Solvation (Poisson-Boltzmann) Periodic Systems (Gaussians) New Functionals DFT(bond breaking) Quantum Monte Carlo methods Time Dependent DFT (optical spectra) Force Fields Polarizable, Charge Transfer Describe Chemical Reactions Describe Phase Transitions Mixed Metal, Ceramic, Polymer MesoScale Dynamics Coarse Grained FF Kinetic Monte Carlo (Gas Diffusion, Epitaxial Growth) Hybrid MD and Meso Dynamics Tribology Utilization: Integrated,Web-based Molecular Dynamics Non-Equilibrium Dynamics Viscosity, rheology Thermal Conductivity Solvation Forces (continuum Solv) surface tension, contact angles Hybrid QM/MD Plasticity Formation Twins, Dislocations Crack Initiation Interfacial Energies Process Simulation Vapor-Liquid Equilibria Reaction Networks Method Developments in MSC Method Development critical to progress Generally not supported by US government or industry

13. Nanotechnology: Experiment and Theory Closing the Gap • Opportunity: Nanotechnology provides tremendous potential for new functional materials (artificial machines smaller than cells) • Problems to be solved before commercialization: • Synthesis • Characterization • Design • In each area there are tremendous experimental challenges. • In each case the time to solution will be dramatically decreased by the use of de novo simulations Multiscale Modeling that couples the time and length scales from electrons and atoms to manufacturing

14. Nanoelectronics Many experimental efforts to make nanoscale electronic devices based on molecules sandwiched between conducting surfaces(e.g., Jim Heath/UCLA-Caltech, Charley Lieber/Harvard, Jan Schön/Lucent, Phaedon Avouris/IBM) This could be most useful.For example a future MEMS-scale device (say 20 microns in size) might have an onboard computer based on nanometer sized elements with built in sensors and logic to respond to local environment without the necessity of communicating to remote computer. Thus to be useful the nanosized switches need not be as fast as current computer elements (GHz). They could be even as slow as KHz and still be useful. Unfortunately little is known about the atomic-level structure and properties of these nanoelectronics systems, making difficult the design of improved devices.

15. Computational Nanoelectronics Step 1: Use theory to predict the structuresand mechanical properties of Nanoelectronics systems Step 2: Use theory to predict electrical performance from 1st principles. To predict electrical performance of experimental systems we must develop QM based methods to predict current/voltage (I/V) performance from first principles. We have been working on this over the last 2 years (with support from an industrial partner). We can now predict I/V both for isolated molecules and for 2-dimensional slabs (still need to make the software faster for routine use). We are now in the position to design new systems that can be synthesized and tested.

16. Stoddart-Heath-Type [2]Rotaxane Molecular Switch DNP=1,5-dioxynaphthalene TTF=tetrathiafulvalene; OFF OFF CBPQT=cyclobis(paraquat-p-phenylene) Weiqiao Deng Yun Hee Jang Seung Soon Jang Hoon Kim [2]Rotaxane

17. Molecular Switch Me 11_26e KAN242 O s +2V  -2.5V 11_26C KAN242 -2.5V  +2V +2.5 V  -2.5 V Return Current 0 Current + + -0 D D redox -1 0 1 + + Volts + + -2 -1 0 1 2 D Voltage D + + Switch diode orientation at –2.3V Fraser Stoddart (UCLA) Jim Heath Caltech) ON OFF NDR=Acceptor Charging(?) TTF Napthyl and TTF nearly equally good donors Rotaxane ring binds to TTF > 300K Rotaxane binds to napthyl > 250K Assume ring moves when apply external voltage which cause diode to switch. TTF Naphthyl Naphthyl OFF ON

18. Atomic level simulation of Current/VoltageFinite (non periodic) case Electrode 2 Transmission function: p(E,V) difference in the Fermi-Dirac occupations between electrodes, 1 and 2 Electrode 1 Green’s function: Molecule HMM obtained from ab initio QM calculation: Overlap matrix S Ab initio Fock matrix H Spectrum functions: Self energy: Formalism due to Mark Ratner Green’s functions for electrodes g1 and g2: Describe as Cluster, slab and surface

19. Predicted I(transmission) -V(energy) Naphthyl, ON TTF, OFF Naphthyl ON V(energy) Not known experimentally which state is on and which is off I(transmission) TTF OFF I(current) H = HM+ Voltage

20. Switch mechanism: Location of HOMO and LUMO Rotaxane on TTF, OFF Rotaxane on Naphthyl, ON HOMO LUMO HOMO LUMO Big gap not coupled. ~insulating Nearly degenerate, thus strongly coupled. ~metallic

21. + + N N O O O M e S S O O O S S O O O – O O O M e –2e + 2 O O O N N + + – +2e O O O M e Ti / Al Ti / Al – – e + + + + + + + + + + + + + – – – – + + + + – e + e + e – e + + + + + + + + + + + + + + + + – + e + + + + + + + + S i S i Next step on Heath-Stoddart molecular devices Get fundamental understanding of how the device is switched. Currently the switching is done using chemical oxidants, reductants(experiments may take minutes) or by applying a voltage step It is not known what the limiting speed is or how it depends on the design The theory has already shown which site blue box sits on in the On/Off states We are now determining how the blue box moves: applied voltage or chemical reductant

22. Research plan: Optimize molecules for devices Can do computational experiments in hours Lab experiments sometimes months R = NO2, CN, COOH, OH etc R = CN:30% increase Connection between molecule tail and electrode

23. Failure of Theory? Bell Labs Molecular Transistor (Schön) Drain Conducting molecules mixed with insulator molecules Drain PURESAM SiO2 MIXED SAM SiO2 Gate Gate Source Source SAM transistor: Nature (2001) Vol, 413, p. 713 Ion/Ioff = 106 Single molecule transistor: Science (2001) Vol 294, p. 2138 Ion/Ioff = 450 at 1:5000 4K temperature • Goals in theoretical Study: • Validate the ability to predict field-effect modulation behavior • Determine the reason for the difference in behavior of these systems • Design new improved systems These papers are now in dispute, Results may have been faked

24. Field-effect modulation behavior Single molecule transistor Experiment (Schoen) theory Shift in Gate voltage can modify MOs near Fermi energy leading to a transistor effect but the maximum effect is only a factor or 20 not the 450 that Schoen reported. Also this value of 20 depends on the optimum placement of the energies of the MOs. Our work was done in Sept. 2001 and not published since it seemed so inconsistent with experiment. Since then the experimental results have been withdrawn because of possible fraud. Thus the theory might be ok. Ion/Ioff = 450 Molecular orbitals shift under Gate voltage, can shift to fermi energy of electrodes Gate voltage theory Predicted field-effect modulation under Gate voltage Ion/Ioff = 20 gate field Drain bias

25. What is the arrangement of Rotaxanes on surface? Assumed Could be... + + + + + + + + + + + + + + + + + + + + + + + + Best performance  Ordered Self Assembled Monolayer L u o – C o l l i e r – J e p p e s e n – N i e l s e n – D e I o n n o – H o – P e r k i n s – T s e n g – Y a m a m o t o – S t o d d a r t – H e a t h

26. SAM of Rotaxane on Au(111) • SAM structures at various packing density • Determine How the SAM structure affects (1) the shuttling motion and (2) the I-V (current-voltage) characteristics Started with half rotaxane 1 (fewer conformations) 1 Bryce, et al. Tetrahed. Lett. (2001), 42, 1143 Bryce, et al. J. Mater. Chem. (2003) 13, 1

27. Validate Force field - Crystal structure VOLMEO (TTF CBPQT4+ 4 PF6 4 CH3CN) UBULUY (TTF PQT2+ 2 PF6) R = 0.094; Philp, JCS, Chem. Commun. (1991) Cooke, Tetrahed. Lett. (2001) X-ray structure vs. average from MD Density 1.59 1.546 (3 % ) 1.8011.789 (0.67 % ) (g/cm3) @ 295 K@ 295 K @ 160 K@ 160 K

28. SAM at various coverages n(1)/n(Au (111) surf) Uncomplexed Up along x Up along y Tilt around y-axis lie down Complexed high low 1/48 (64r3) 3.46 nm2/1 1/12 (32r3) 0.86 1/18 c(92r3) 1.30 1/24 c(64r3) 1.73 1/27 c(93r3) 1.94 1/36 (63r3) 2.59

29. Most stable packing  coverage of [0.9, 1.3] (nm2/1) SAM 1/15 (footage 1.08 nm2/1) SAM 1/12 (footage 0.86 nm2/1) Stand up! Ring face (PQT or Ph) parallel to surface: -contact?

30. Now do full rotaxane 2 (DNP added with ethylene oxide linker) 2 SAM 1/12 (footage 0.86 nm2/2) SAM 1/24 (footage 1.73 nm2/2) Good -contact between stations

31. p-Stacking arrangement in [2]rotaxane SAM? Ideal, assumed + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + z need to understand the “shoulder-to-shoulder sticking” versus “p-stacking” on the surface. This Could be better...

32. Electronic Structure of Model [2]Rotaxane (with shuttle) (TTF)(CBPQT)(PF6)4(DNP) “CBPQT@TTF” HOMO1 (DNP) HOMO (TTF + CBPQT) • Significant overlap • Shifted to lower energy LUMO (CBPQT) • LUMO+1: CBPQT + TTF • LUMO, LUMO+1 Splitting (TTF)(DNP)(CBPQT)(PF6)4 “CBPQT@DNP” HOMO1 (DNP) HOMO (TTF) LUMO (CBPQT) Ring provides low-lying LUMO’s. Ring stabilizes energy level of nearby station. Only  orbitals around EF

33. Two Plausible, Conformation-Dependent, Tunneling Mechanisms in [2]Rotaxane extended configuration Better tunneling between aligned HOMOs (each at each station: folded configuration Better tunneling between aligned HOMO (free station) and LUMO (ring): Need direct contact between free station and CBPQT such as folding and -contact

34. Exper. UCLA Theory: Goddard, Caltech

35. Manipulate Graphene, Graphite, and Single Walled Carbon Nanotubes Motivation: Hongjai Dai, J. Am. Chem. Soc. 2001, 123, 3838-3839 The experiment provided evidence of 1-PBSE absorption by imaging gold clusters presumably attached to the ester tails of the molecules absorbed on SWNT, but what is really happening? 1-Pyrene Butanoic Acid Succinimidyl Ester concept Purpose: Understand the interaction of 1-PBSE with carbon nanotubes and with one another so that we can use non-covalent sidewall functionalization of carbon nanotubes to for molecular electronics and self assembly.

36. Methods Step One: Find out how different parts of PBSE interact with one another in free space. Step Three: Look at the dynamics of isolated PBSE clusters on graphene and graphite. Step Two: Do the same with a PBSE dimer. Step Four: Examine packed configurations for pyrene and PBSE on graphene and graphite (check this against experimental results if possible). Each pyrene covers 50 graphene atoms, each PBSE can cover 24 or 40 atoms.

37. More on Methods Step Six: Put PBSE on (10,10) nanotube and compare the free energies of different packing configurations. Try different nanotube sizes and chiralities. Validating Tools – Bonding forces: We should have the right shape for our molecules. Validating Tools – Friction: Our tools need to produce the right energy barrier for translation of the absorbed molecules on the graphene surface. We should have the correct stresses for the shearing of graphite. Validating Tools – Non-Bond forces: We should produce the correct inter-plane separation in graphite. Our QEq parameters should give the right charges.

38. Surprises So Far Pyrene Ester tail PBSE 4x5 PBSE 4x3 For isolated PBSE clusters on graphite, both the ester tail and the pyrene part of PBSE like to lay flat. On Graphene, Coulombic interactions between neighboring PBSE’s has led to tighter than expected optimum packing of PBSE. Whereas a single pyrene covered 50 graphene atoms, a single PBSE can cover 24 or 40 graphene atoms. Results on graphite and nanotubes are pending. Van der Waals interaction is responsible for absorption onto graphite, graphene, and nanotube, but there is strong Coulombic interaction between absorbed PBSE’s.

39. Summary nanoelectronics • SAM packing on Au(111) from MD simulation  Coverage-dependence conformation (-stacking) • Electronic structure of essential components from QM •  Role of the ring 1: provide low-lying LUMO’s •  Role of the ring 2: stabilize levels of nearby stations •  -orbitals dominant around HOMO-LUMO • (Aliphatic linkers and anchors negligible?) • (3) I-V Calculation from periodic QM and Green’s matrix on • a. Fully extended (unfolded) form • b. Fully folded form • c. Fully folded form w/o linker/anchor Conformation effect on I-V Thru-bond effect on I-V

40. Application: Ferroelectric Actuators Must understand role of domain walls in mediate switching 1.0 E 2 Experiments in BaTiO3 Strain (%) Domain walls lower the energy barrierby enabling nucleation and growth 0 1 -10,000 0 10,000 90° domain wall Electric field (V/cm) Switching gives large strain, … but energy barrier is extremely high! Essential questions: Are domain walls mobile? Do they damage the material? In polycrystals? In thin films? Use MD with ReaxFF

41. P-QEq Force Field Model Proper description of Electrostatics is critical • Include Electrostatic interactions between all atoms (ECoulomb) • Describe Charges as distributed (Gaussians) • not point charges • Core charge is fixed to the mass of the atom • (total charge +4 for Ti) • Electron or shell charge is allowed to move • wrt the core (atomic polarizability) • This includes Shielding as charges overlap • Allow charge transfer (shell charges not fixed) • Self-consistent charge equilibration • Pair-wiseNonbond Terms between all atoms • Short range Pauli Repulsion plus Dispersion(EvdW)

42. Charge Equilibration (QEq): Environment dependent charges: Electrostatic energy Atomic self energy Pairwise electrostatic interaction (Shielded Coulomb) Charge Equilibration (QEq) Require that the chemical potential (dE/dQi) be the same at every atom Fix core charge, allow valence charge to transfer and to shift center Five universal parameters for each element describes charge distribution, polarization QEq parameters are fitted to reproduce QM charges on molecules and polarizability of atoms Original Paper: Rappe and Goddard, J. Phys. Chem. 1991

43. Pauli Principle and Dispersion Terms Distance energy Use simple Morse Form with 3 universal parameters per ij (R0, D0, ): Same parameters for same pair of atoms in all environments Determine from QM at very close separations 44

44. Phase transitions in BaTiO3 from MD Polarizable ReaxFF Rhomb. Ortho. Tetra. Cubic

45. Transition Temperature (K) Spontaneous Polarization (uC/cm2) * Merz, W. J., Phys. Rev. 76, 1221 (1949) 46

46. Hysterisis Loop of BaTiO3 at 300K, 25GHz by MD Dz (V/A) Applied Field (25 GHz) Time (ps) Polarization (mC/cm2) Applied Field(V/A) Electric Displacement Correction Dipole Correction Apply Dz at f=25GHz (T=40ps). T=300K. Monitor Pz vs. Dz. Pr Ec Get Pz vs. Ez. Ec = 0.05 V/A at f=25 GHz. 47

47. O Vacancy Jump When Applying Strain z z y y o x x O atom O vacancy site X-direction strain induces x-site O vacancies (i.e., neighboring Ti’s in x direction) to y or z-sites. 48

48. Effect of O Vacancy on the Hystersis Loop Pr Ec Supercell: 2x32x2 Total Atoms: 640/639 Perfect Crystal without O vacancy Crystal without 1 O vacancy. O Vacancy jumps when domain wall sweeps. • Introducing O Vacancy reduces both Pr & Ec. • O Vacancy jumps when domain wall sweeps. Can look at bipolar case where switch domains from x to y 49

49. Computational design: Nano-actuator Pt electrodes Si substrate PVDF chains • Nano-assembled structures • Isolated PVDF chains prefer combination of Trans and Gauch conformations • Control the packing density by assembling PVDF chains between Si slabs • when packing density is low  structure contains Trans and Gauch conformations • Can convert to All Trans with an electric field (get large strains, high frequency)

50. Computational design: nano-actuator Si (111) surface PVDF: 1/2 coverage 10 monomer long chains Play movie