ChE/MSE 557 Fall 2006 1Computational Nanoscience of Soft Materialssglotzer@umich.edu

ChE/MSE 557Intro part 2

What is the role of simulationin nanoscience research?

ChE/MSE 557 Fall 2006 2Computational Nanoscience of Soft Materialssglotzer@umich.edu

Opportunities for Simulation

• Simulation– Extends window of observation

– Helps interpret experimental results– Provides tests of new theories

and predictions for experiment

Simulation complements both experiment and theory.

ChE/MSE 557 Fall 2006 3Computational Nanoscience of Soft Materialssglotzer@umich.edu

Opportunities for Simulation: 2006

• Enormous gains in computer– Speed -

• processors, bus, memory access– Memory– Storage– Affordability– Accessibility– Ease of use

Computer simulation is notjust for the selected few anymore: it’s mainstream!

ChE/MSE 557 Fall 2006 4Computational Nanoscience of Soft Materialssglotzer@umich.edu

Model vs. Method

• Using computational science to study materialsphenomena involves both a model and a method.

– The model captures the essential features of thephenomena we wish to describe.

– The simulation method is what we use to study themodel.

– Sometimes, the model and the method are intertwinedand considered together in a simulation approach.

ChE/MSE 557 Fall 2006 5Computational Nanoscience of Soft Materialssglotzer@umich.edu

Modeling Materials Phenomena

• How do we describe (i.e. make a model for) a material or aphenomenon?– E.g.

• flow of DNA through a membrane• interaction of a dendrimer with a cell wall• clay particles dispersed in a polymer• crystallization of a liquid within a nanopore• nanotubes aligned on polymer-templated microchip• DNA-tethered nanocrystal in solution• Nanocolloidal assembly• …

ChE/MSE 557 Fall 2006 6Computational Nanoscience of Soft Materialssglotzer@umich.edu

Modeling Materials Phenomena

• There are many possible levels of description; choosingamong them depends on your goals and on the availabletools.

• In building a model, we must make decisions, eitherexplicitly or implicitly, about what is important for thequestions we seek to answer.

ChE/MSE 557 Fall 2006 7Computational Nanoscience of Soft Materialssglotzer@umich.edu

Modeling Materials Phenomena

specific

numerical

stochastic

microscopic

discrete

qualitative

general

analytical

deterministic

macroscopic

continuous

quantitative

No “best” model. Depends on the question, and on the investigator. Different standards for success.

ChE/MSE 557 Fall 2006 8Computational Nanoscience of Soft Materialssglotzer@umich.edu

Simulating Materials Phenomena

• Choosing which simulation method to use depends on the level of description of the model, the phenomena we wish to study, and the questions we seek to answer.

• Some of the simulation methods used to study soft matter are also used to study hard matter, and some are special to soft matter (usually those at the mesoscale).

After choosing a model, choose a method.

ChE/MSE 557 Fall 2006 9Computational Nanoscience of Soft Materialssglotzer@umich.edu

Simulation of Soft Matter

What are the challenges?

ChE/MSE 557 Fall 2006 10Computational Nanoscience of Soft Materialssglotzer@umich.edu

Computational Challenges of Soft Matter

Soft materials are computationally challenging due to :• Wide range of length scales: Å - mm• Wide range of time scales: fs - years

– Complex nature of individual molecules– Hierarchical, cooperative nature of structure and assembly– Formation from complex liquid state– Can be far from equilibrium– Often amorphous– Viscoelasticity -> complex response

• Interfaces• Dissimilar materials

Is “soft” special?

Polymers, foams, emulsions, surfactants, liquid crystals, gels, DNA, colloids, proteins, connective tissue, membranes, cells, …

No one (or two) methods will suffice!

ChE/MSE 557 Fall 2006 11Computational Nanoscience of Soft Materialssglotzer@umich.edu

Brief Overview

Simulation methods for softmaterials

ChE/MSE 557 Fall 2006 12Computational Nanoscience of Soft Materialssglotzer@umich.edu

Simulation Methods for Soft MaterialsTi

me

Scal

e (s

ec)

Length Scale

pico

Angstroms nanometers microns mm

AbInitio

metersfemto

nano

micro

millise

c MacroscaleSimulation

ElectronicStructure - MO & DFTAb initio MDQuantum MC

MesoscaleSimulation Finite

element

MolecularSimulation

Brownian DynamicsLattice BoltzmannCellular AutomataDPDDDFTMolecular dynamics

Monte Carlo

CFDMech

ChE/MSE 557 Fall 2006 13Computational Nanoscience of Soft Materialssglotzer@umich.edu

Ab initio methods

ChE/MSE 557 Fall 2006 14Computational Nanoscience of Soft Materialssglotzer@umich.edu

Molecular Dynamics for Soft Matter

• EA/UA Atom MDE.g. Lubrication

in nanoscale gapsFor dodecane between mica- 6 orders increase in µ- 7 orders lower for

transition to Newtonian flow

• Coarse-grained MDE.g. nano-filled polymer melt– Molecular packing and dynamics near nanoparticle surface– Effect of np/polymer interactions on processing parameters

Starr, Schroder, Glotzer, PRE 64, 021802-1, 2001

S. T

. Cui

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ChE/MSE 557 Fall 2006 15Computational Nanoscience of Soft Materialssglotzer@umich.edu

T = 7dN = 72

T = 13dN = 132

T = 7lN = 72

T = 13lN = 132

bacteriophage HK 97Simulated Structure

rhesus rotavirus Simulated Structure

Murine Polyomavirus

Simulated Structure

Bursal diseasevirus

Simulated Structure

The Glotzer Group @ University of Michiganhttp://viperdb.scripps.edu

Monte Carlo simulation

ChE/MSE 557 Fall 2006 16Computational Nanoscience of Soft Materialssglotzer@umich.edu

Brownian dynamics simulations

Self-assemblyof tetherednano buildingblocks

Zhang, Horsch,Lamm, Glotzer,Nano Letters, 2003.

ChE/MSE 557 Fall 2006 17Computational Nanoscience of Soft Materialssglotzer@umich.edu

Dissipative Particle Dynamics

Surfactant self-assembly on nanostructured surfaces

length red,yellow = 4,7red:yellow = 1:1

length red,yellow = 4,4red:yellow = 1:1

Chetana Singh

ChE/MSE 557 Fall 2006 18Computational Nanoscience of Soft Materialssglotzer@umich.edu

Field Theoretic Methods for Soft Matter

3-d Patterning at the Nanoscale Nanotemplating

“Nanofillers”

S.C. Glotzer, 1995

B.P.

Lee

, J.F

. Dou

glas

, &

S.C.

Glo

tzer

, 199

9

B.P. Lee, J.F. Douglas, SCG 1998.

- photonic devices- scaffolds for molecular electronics, tissue growth- high strength nanocomposites

ChE/MSE 557 Fall 2006 19Computational Nanoscience of Soft Materialssglotzer@umich.edu

We’ll learn aboutstrategies for bridginglength and time scales

Simulation Methods for Soft MaterialsTi

me

Scal

e (s

ec)

Length Scale

pico

Angstroms nanometers microns mm

AbInitio

metersfemto

nano

micro

millise

c MacroscaleSimulation

ElectronicStructure - MO & DFTAb initio MDQuantum MC

MesoscaleSimulation Finite

element

MolecularSimulation

Brownian DynamicsLattice BoltzmannCellular AutomataDPDDDFTMolecular dynamics

Monte Carlo

CFDMech

ChE/MSE 557 Fall 2006 20Computational Nanoscience of Soft Materialssglotzer@umich.edu

Holy Grail: “In silico” nano-scale design

From molecular processes to macroscopic properties

Mesoscale

Atomistic

Macroscale

Molecular/mesoscale

Example:“Designed” polymernanocomposite

First principles

• Seamless linking of nanoscale processes to macroscopic properties.