Nanomaterials

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Nanomaterials

• Boxuan Gu and David McQuilling

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What are they?

• Nano 10-9 or one billionth in size
• Materials with dimensions and tolerances in the
  range of 100 nm to 0.1 nm
• Metals, ceramics, polymeric materials, or
  composite materials
• One nanometer spans 3-5 atoms lined up in a row
• Human hair is five orders of magnitude larger
  than nanomaterials

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Nanomaterial Composition

• Comprised of many different elements such as
  carbons and metals
• Combinations of elements can make up nanomaterial
  grains such as titanium carbide and zinc sulfide
• Allows construction of new materials such as C60
  (Bucky Balls or fullerenes) and nanotubes

4
How they are made

• Clay/polymer nanocomposites can be made by
  subjecting clay to ion exchange and then mixing
  it with polymer melts
• Fullerenes can be made by vaporizing carbon
  within a gas medium
• Current carbon fullerenes are in the gaseous
  phase although samples of solid state fullerenes
  have been found in nature

5
Bucky Ball properties

• Arranged in pentagons and hexagons
• A one atom thick seperation of two spaces
  inside the ball and outside
• Highest tensile strength of any known 2D
  structure or element, including cross-section of
  diamonds which have the highest tensile strength
  of all known 3D structures (which is also a
  formation of carbon atoms)
• Also has the highest packing density of all known
  structures (including diamonds)
• Impenetrable to all elements under normal
  circumstances, even a helium atom with an energy
  of 5eV (electron Volt)

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Bucky Ball properties cont.

• Even though each carbon atom is only bonded with
  three other carbons (they are most happy with
  four bonds) in a fullerene, dangling a single
  carbon atom next to the structure will not affect
  the structure, i.e. the bond made with the
  dangling carbon is not strong enough to break the
  structure of the fullerene
• No other element has such wonderful properties as
  carbon which allows costs to be relatively cheap
  after all its just carbon and carbon is
  everywhere

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Buckminsterfullerene uses

• Due to their extremely resilient and sturdy
  nature bucky balls are debated for use in combat
  armor
• Bucky balls have been shown to be impervious to
  lasers, allowing for defenses from future warfare
• Bucky balls have also been shown to be useful at
  fighting the HIV virus that leads to AIDS
• Researchers Kenyan and Wudl found that water
  soluble derivates of C60 inhibit the HIV-1
  protease, the enzyme responsible for the
  development of the virus
• Elements can be bonded with the bucky ball to
  create more diverse materials including
  superconductors and insulators
• Can be used to fashion nanotubes

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Bucky Balls
C240 colliding with C60 at 300 eV (Kinetic energy)
Bucky Ball (C60)
http//www.pa.msu.edu/cmp/csc/simindex.html
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Nanotube properties

• Superior stiffness and strength to all other
  materials
• Extraordinary electric properties
• Reported to be thermally stable in a vacuum up to
  2800 degrees Centigrade (and we fret over CPU
  temps over 50o C)
• Capacity to carry an electric current 1000 times
  better than copper wires
• Twice the thermal conductivity of diamonds
• Pressing or stretching nanotubes can change their
  electrical properties by changing the quantum
  states of the electrons in the carbon bonds
• They are either conducting or semi-conducting
  depending on the their structure

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Nanotube uses

• Can be used for containers to hold various
  materials on the nano-scale level
• Due to their exceptional electrical properties,
  nanotubes have a potential for use in everyday
  electronics such as televisions and computers to
  more complex uses like aerospace materials and
  circuits

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Nanotubes
Switching nanotube-based memory
Carbon based nanotubes
http//www.pa.msu.edu/cmp/csc/simindex.html
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Applications of Nanotechnology

• Next-generation computer chips
• Ultra-high purity materials, enhanced thermal
  conductivity and longer lasting nanocrystalline
  materials
• Kinetic Energy penetrators (DoD weapon)
• Nanocrystalline tungsten heavy alloy to replace
  radioactive depleted uranium
• Better insulation materials
• Create foam-like structures called aerogels
  from nanocrystalline materials
• Porous and extremely lightweight, can hold up to
  100 times their weight

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More applications

• Improved HDTV and LCD monitors
• Nanocrystalline selenide, zinc sulfide, cadmium
  sulfide, and lead telluride to replace current
  phosphors
• Cheaper and more durable
• Harder and more durable cutting materials
• Tungsten carbide, tantalum carbide, and titanium
  carbide
• Much more wear-resistant and corrosion-resistant
  than conventional materials
• Reduces time needed to manufacture parts, cheaper
  manufacturing

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Even more applications

• High power magnets
• Nanocrystalline yttrium-samarium-cobalt grains
  possess unusually large surface area compared to
  traditional magnet materials
• Allows for much higher magnetization values
• Possibility for quieter submarines,
  ultra-sensitive analyzing devices, magnetic
  resonance imaging (MRI) or automobile alternators
  to name a few
• Pollution clean up materials
• Engineered to be chemically reactive to carbon
  monoxide and nitrous oxide
• More efficient pollution controls and cleanup

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Still more applications

• Greater fuel efficiency for cars
• Improved spark plug materials, railplug
• Stronger bio-based plastics
• Bio-based plastics made from plant oils lack
  sufficient structural strength to be useful
• Merge nanomaterials such as clays, fibers and
  tubes with bio-based plastics to enhance strength
  and durability
• Allows for stronger, more environment friendly
  materials to construct cars, space shuttles and a
  myriad of other products

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Applications wrapup

• Higher quality medical implants
• Current micro-scale implants arent porous enough
  for tissue to penetrate and adapt to
• Nano-scale materials not only enhance durability
  and strength of implants but also allow tissue
  cells to adapt more readily
• Home pregnancy tests
• Current tests such as First Response use gold
  nanoparticles in conjunction with micro-meter
  sized latex particles
• Derived with antibodies to the human chorionic
  gonadotrophin hormone that is released by
  pregnant women
• The antibodies react with the hormone in urine
  and clump together and show up pink due to the
  nanoparticles plamson resonance absortion
  qualities

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Modeling and Simulation of Nanostructured
Materials and Systems
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Preface

• Each distinct age in the development of humankind
  has been associated with advances in materials
  technology.
• Historians have linked key technological and
  societal events with the materials technology
• that was prevalent during the stone age,
  bronze age, and so forth.

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Significant events In materials

• 1665 - Robert Hooke material microstructure
• 1808 - John Dalton atomic theory
• 1824 - Portland cement
• 1839 - Vulcanization
• 1856 - Large-scale steel production
• 1869 - Mendeleev and Meyer Periodic Table of
  the Chemical Elements
• 1886 - Aluminum
• 1900 - Max Planck . quantum mechanics

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Cont.

• 1909 - Bakelite
• 1921 - A. A. Griffith . fracture strength
• 1928 - Staudinger polymers (small molecules that
  link to form chains)
• 1955 - Synthetic diamond
• 1970 - Optical fibers
• 1985 - First university initiatives attempt
  computational materials design
• 1985 - Bucky balls (C60) discovered at Rice
  University
• 1991 - Carbon nanotubes discovered by Sumio
  Iijima

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Why we need Computational Materials?

• Traditionally, research institutions have relied
  on a discipline-oriented approach to material
• development and design with new materials.
• It is recognized, however, that within the scope
  of materials and structures research, the breadth
  of length and time scales may range more than 12
  orders of
• magnitude, and different scientific and
  engineering disciplines are involved at each
  level.

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• To help address this wide-ranging
  interdisciplinary research, Computational
  Materials has been formulated with the specific
  goal of exploiting the tremendous physical and
  mechanical properties of new nano-materials by
  understanding materials at atomic, molecular, and
  supramolecular levels.

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• Computational Materials at LaRC draws from
  physics and chemistry, but focuses on
  constitutive descriptions of materials that are
  useful in formulating macroscopic models of
  material performance.

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Benefit of Computational materials

• First, it encourages a reduced reliance on costly
  trial and error, or serendipity, of the
  Edisonian approach to materials research.
• Second, it increases the confidence that new
  materials will possess the desired properties
  when scaled up from the laboratory level, so that
  lead-time for the introduction of new
  technologies is reduced.
• Third, the Computational Materials approach
  lowers the likelihood of conservative or
  compromised designs that might have resulted from
  reliance on less-than-perfect materials.

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Schematic illustration of relationships between
time and length scales for the multi-scale
simulation methodology.
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Cont.

• The starting point is a quantum description of
  materials this is carried forward to an
  atomistic scale for initial model development.
• Models at this scale are based on molecular
  mechanics or molecular dynamics.

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Cont.

• At the next scale, the models can incorporate
  micro-scale features and simplified constitutive
  relationships.
• Further progress up, the scale leads to the meso
  or in-between levels that rely on combinations of
  micromechanics and wellestablished theories such
  as elasticity.

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Cont.

• The last step towards engineering-level
  performance is to move from mechanics of
  materials to structural mechanics by using
  methods that rely on empirical data,constitutive
  models, and fundamental mechanics.

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Nanostructured Materials

• The origins of focused research into
  nanostructured materials can be traced back to a
  seminal lecture given by Richard Feynman in
  19591.
• In this lecture, he proposed an approach to the
  problem of manipulating and controlling things on
  a small scale. The scale he referred to was not
  the microscopic scale that was familiar to
  scientists of the day but the unexplored
  atomistic scale.

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• The nanostructured materials based on carbon
  nanotubes and related carbon structures are of
  current interest for much of the materials
  community.
• More broadly then, nanotechnology presents the
  vision of working at the molecular level, atom by
  atom, to create large structures with
  fundamentally new molecular organization.

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Simluation methods
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Atomistic, Molecular Methods

• The approach taken by the Computational Materials
  is formulation of a set of integrated predictive
  models that bridge the time and length scales
  associated with material behavior from the nano
  through the meso scale.

33

• At the atomistic or molecular level, the reliance
  is on molecular mechanics,
• molecular dynamics, and coarse-grained,
  Monte-Carlo simulation.
• Molecular models encompassing thousands and
  perhaps millions of atoms can be solved by these
  methods and used to predict fundamental,
  molecular level material behavior. The methods
  are both static and dynamic.

34

• Molecular dynamics simulations generate
  information at the nano-level, including atomic
  positions and velocities.
• The conversion of this information to macroscopic
  observables such as pressure, energy, heat
  capacities, etc., requires statistical mechanics.

35

• An experiment is usually made on a macroscopic
  sample that contains an extremely large number of
  atoms or molecules, representing an enormous
  number of conformations.
• In statistical mechanics, averages corresponding
  to experimental measurements are defined in terms
  of ensemble averages.

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For example
where M is the number of configurations in the
molecular dynamics trajectory and Vi is the
potential energy of each configuration.
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where M is the number of configurations in the
simulation, N is the number of atoms in the
system, mi is the mass of the particle i and vi
is the velocity of particle i. To ensure a
proper average, a molecular dynamics simulation
must account for a large number of representative
conformations.
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• By using Newtons second law to calculate a
  trajectory, one only needs the initial positions
  of the atoms, an initial distribution of
  velocities and the acceleration, which is
  determined by the gradient of the potential
  energy function.
• The equations of motion are deterministic i.e.,
  the positions and the velocities at time zero
  determine the positions and velocities at all
  other times, t. In some systems, the initial
  positions can be obtained from experimentally
  determined structures.

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• In a molecular dynamics simulation, the time
  dependent behavior of the molecular system is
  obtained by integrating Newtons equations of
  motion.
• The result of the simulation is a time series of
  conformations or the path followed by each atom.
• Most molecular dynamics simulations are performed
  under conditions of constant number of atoms,
  volume, and energy (N,V,E) or constant number of
  atoms, temperature, and pressure (N,T,P) to
  better simulate experimental conditions.

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Basic steps in the MD simulation

• 1. Establish initial coordinates.
• 2. Minimize the structure.
• 3. Assign initial velocities.
• 4. Establish heating dynamics.
• 5. Perform equilibration dynamics.
• 6. Rescale the velocities and check if the
  temperature is correct.
• 7. Perform dynamic analysis of trajectories.

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Monte Carlo Simulation

• Although molecular dynamics methods provide the
  kind of detail necessary to resolve molecular
  structure and localized interactions, this
  fidelity comes with a price. Namely, both the
  size and time scales of the model are limited by
  numerical and computational boundaries.

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• To help overcome these limitations,coarse-grained
  methods are available that represent molecular
  chains as simpler, bead-spring models.
• Coarse-grain models are often linked to Monte
  Carlo (MC) simulations to provide a timely
  solution.
• The MC method is used to simulate stochastic
  events and provide statistical approaches to
  numerical Integration.

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• There are three characteristic steps in the MC
  simulation that are given as follows.
• 1. Translate the physical problem into an
  analogous probabilistic or statistical model.
• 2. Solve the probabilistic model by a numerical
  sampling experiment.
• 3. Analyze the resultant data by using
  statistical methods.

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Continum Methods

• Despite the importance of understanding the
  molecular structure and nature of materials, at
  some level in the multi-scale analysis the
  behaviour of collections of molecules and atoms
  can be homogenized.

45

• At this level, the continuum level, the observed
  macroscopic behaviour is explained by
  disregarding the
• discrete atomistic and molecular structure and
  assuming that the material is continuously
  distributed throughout its volume.
• The continuum material is assumed to have an
  average density and can be subjected to body
  forces such as gravity and surface forces such as
  the contact between two bodies.

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• The continuum can be assumed to obey several
  fundamental laws.
• The first, continuity, is derived from the
  conservation of mass.
• The second, equilibrium, is derived from momentum
  considerations and Newtons second law.
• The third, the moment of momentum principle, is
  based on the model that the time rate of change
  of angular momentum with respect to an arbitrary
  point is equal to the resultant moment.

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• These laws provide the basis for the continuum
  model and must be coupled with the appropriate
  constitutive equations and equations of state to
  provide all the equations necessary for solving a
  continuum problem.
• The state of the continuum system is described by
  several thermodynamic and kinematic state
  variables.
• The equations of state provide the relationships
  between the non-independent state variables.

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• The continuum method relates the deformation of a
  continuous medium to the external forces acting
  on the medium and the resulting internal stress
  and strain.
• Computational approaches range from simple
  closed-form analytical expressions to
  micromechanics to complex structural mechanics
  calculations basedon beam and shell theory.

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• The continuum-mechanics methods rely on
  describing the geometry, (I.e.physical model),
  and must have a constitutive relationship to
  achieve a solution.
• For a displacement based form of continuum
  solution, the principle of virtual work is
  assumed valid.

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In general, this is given as
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where W is the virtual work which is the work
done by imaginary or virtual displacements, is
the strain, is the stress, P is the body force, u
is the virtual displacement, T is the tractions
and F is the point forces. The symbol is the
variational operator designating the virtual
quantity. For a continuum system, a necessary
and sufficient condition for equilibrium is that
the virtual work done by sum of the external
forces and internal forces vanish for any virtual
displacement.
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Software for Nanomaterials
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BOSS-Biochemical and Organic Simulation System

• The B O S S program performs (a) Monte Carlo (MC)
  statistical mechanics simulations for solutes in
  a periodic solvent box, in a solvent cluster, or
  in a dielectric continuum including the gas
  phase, and (b) standard energy minimizations,
  normal mode analysis, and conformational
  searching.

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XMakemol

• XMakemol is a mouse-based program, written using
  the LessTif widget set, for viewing and
  manipulating atomic and other chemical systems.
  It reads XYZ input and renders atoms, bonds and
  hydrogen bonds.

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Features

• Animating multiple frame files
• Interactive measurement of bond lengths, bond
  angles and torsion angles
• Control over atom/bond sizes
• Exporting to XPM, Encapsulated PostScript and Fig
  formats
• Toggling the visibility of groups of atoms
• Editing the positions of subsets of atoms

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A water molecule with vectors along the principal
axes
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As above, with lighting turned off
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Candidate structure for the H2O(20) global
minimum
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Buckminster Fullerene
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Amsterdam Density Functional (ADF) package

• The Amsterdam Density Functional (ADF) package is
  software for first-principles electronic
  structure calculations. ADF is used by academic
  and industrial researchers worldwide in such
  diverse fields as pharmacochemistry and materials
  science

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• It is currently particularly popular in the
  research areas of
• homogeneous and heterogeneous catalysis
• inorganic chemistry
• heavy element chemistry
• various types of spectroscopy
• biochemistry

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ARP/wARP 
ARP/wARP  is a package for automated protein
model building and structure refinement. It is
based on a unified approach to the structure
solution process by combining electron density
interpretation using the concept of the hybrid
model, pattern recognition in an electron density
map and maximum likelihood model parameter
refinement.
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• The ARP/wARP suite is under continuous
  development. The present release, Version 6.0,
  can be used in the following ways
• Automatic tracing of the density map and model
  building. This includes the refinement of MR
  solutions and the improvement of MAD and
  M(S)IR(AS) phases via map interpretation
• Free atoms density modification
• Building of the solvent structure

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Chemsuite - A suite designed for chemistry on
Linux

• Chemsuite is composed by several program
• Chem2D A 2D molecular drawer.
• Molcalc A molecular weight calculator  
• ChemModel3D Molecular 3D modeler
• ChemIR An infrared spectra processor.
• It can read, process, export and print Perkin
  Elmerspectra.
• ChemNMR 1D NMR Processor
• ChemMC Monte carlo Simulator and Integrator

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General Atomic and Molecular Electronic Structure
System (GAMESS)

• GAMESS is a program for ab initio quantum
  chemistry. Briefly, GAMESS can compute SCF
  wavefunctions ranging from RHF, ROHF, UHF, GVB,
  and MCSCF. Correlation corrections to these SCF
  wavefunctions include Configuration Interaction,
  second order perturbation theory, and
  Coupled-Cluster approaches, as well as the
  Density Functional Theory approximation.

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Useful site

• http//www.linuxlinks.com/Software/Scientific/Chem
  istry/