View
215
Download
0
Category
Tags:
Preview:
Citation preview
Basic Energy Sciences Advisory Committee Meeting
Omni Shoreham Hotel Washington, DCJune 6, 2005
Harriet Kung Division of Materials Sciences and EngineeringOffice of Basic Energy Sciences, Office of ScienceU.S. Department of Energy
Division of Materials Sciences and EngineeringDivision of Materials Sciences and Engineering
Reflection on BESAC Report on Theory and ComputationReflection on BESAC Report on Theory and Computation
Basic Energy SciencesBasic Energy SciencesServing the Present, Shaping the FutureServing the Present, Shaping the Future
Dramatic Progress in Theory and ModelingDFT, ab initio MD, Quantum MC, DMFT, etc.
New Computational CapabilitiesWorkstation and Cluster- Universities and Labs Massively Parallel Computers- LBNL/NERSC, PNNL/EMSL, ANL, ORNL
Theory and Computation Theory and Computation A Confluence of Opportunities in Materials Sciences and Engineering A Confluence of Opportunities in Materials Sciences and Engineering
0.78 Angstroms
Direct image of a silicon crystal showing atom columns in pairs only 0.78 Angstroms apart
A first-principles method describing the dynamics of magnetic moments in materials Charge Transport in Carbon Nanotubes
Source: A.P. Alivisatos
New Scientific FrontiersUltrasmall and Ultrafast Sciences, Quantum-Level Control of Matter and Information, Infusion of Bio Approaches and Techniques
Source: A.P. Alivisatos
New Experimental CapabilitiesTabletop Tools: STM, NMR, STEM, fs-LaserLarge Facilities: SNS, NSRCs, LCLS
Source: G.M. Stocks et al.
Source: S. Pennycook et al.
Theory and Computation in Materials Sciences and EngineeringTheory and Computation in Materials Sciences and Engineering
Electronic Structure Band structure, simulations, model development, many body theory, spin dynamics Correlation of electronic structure with materials properties; self-organized electronic structure (FQHE, stripes); superconductivity, magnetism, chemical reactivity, hardness, toughness Dynamics & fluctuations
New Materials
New combinations of atoms and new degrees of complexity, e.g., competing interactions among spin, charge, lattice, Vortex matter, Photonic Band Gap Materials, Granular Materials Nano and other low-dimensional structures Materials created by energetic processes Self assembly, pattern formation Modeling complex fluids, colloids, polymers, and biomolecular materials
Surfaces and Interfaces Electronic surface structure, surface reconstruction Patterns of crystal growth Solid – liquid interfaces, corrosive, adhesive, and electrochemical properties Defects in solids
Development of Computational Techniques Spin Dynamics, Inverse Band Structure, Linear Expansion in Geometric Objects, Algorithm Development, Hyperdynamics
Nanoscale ScienceNanoscale Science
Biomimetic Materials and Energy Processes Biomimetic Materials and Energy Processes
Correlated Electrons in Solids Correlated Electrons in Solids
Excited Electronic StatesExcited Electronic States
Magnetic Spin Systems & Single Electron DevicesMagnetic Spin Systems & Single Electron Devices
Defects in Solids Defects in Solids
Control of Energy, Matter & Information at the Quantum LevelControl of Energy, Matter & Information at the Quantum Level
Ultrafast Physics and ChemistryUltrafast Physics and Chemistry
Control of Chemical TransformationsControl of Chemical Transformations
New Opportunities Identified by the Report Match DMS&E PrioritiesNew Opportunities Identified by the Report Match DMS&E Priorities
Simulations of Self Assembly of Gold NanoparticlesSimulations of Self Assembly of Gold Nanoparticles
► Simulations have explored formation of nanocrystals composed of passivated gold clusters.
► Assembly begins by formation of chain structures. The length of the chains formed as well as the nanoparticle size and temperature all affect the resulting properties such as tetragonality, elastic properties of the lattice.
► Another related project has been examining how nanoparticles can be tailored to encourage chosen structures. (i.e., polymer tethers, reactive regions, etc.)
New insights on self assembly of nanoparticles were provided by atomistic simulations.DMS&E Theoretical Condensed Matter Physics CRA
Atomistic simulations are being used to gain insight on the unit processes involved in deformation. This array of pyramids was revealed by computer simulations as the structure of Cu/Ni interfaces and consists of defects known as stair-rods and stacking faults. The computer models also indicate that this structure is very resistant to deformation.
Theoretical Strength - Deformation in Nanostructured MetalsTheoretical Strength - Deformation in Nanostructured Metals
Cu
Ni
Cu
Ni
As-deposited Under applied strain 3-D view of the interface structure
Computation studies shed light on the role of defects in controlling ultimate strength in solids. DMS&E Mechanical Behavior CRA
k||-resolved contributions from Fe(001) minority states to the STM current (n1) and corrugation (n2) for different applied fields. Yellow (red) denotes positive (negative) values.
Charge density above the Fe(001) surface showing the anticorrugation for an applied electric field.
Scanning Tunneling Microscope data are normally interpreted as directly giving the positions of the atoms on a surface. Calculations of the effect indicate situations where the electric field induced by the tip modify the electronic densities and give false indications for the atomic positions.
New Ideas Underlie Experimental InterpretationsNew Ideas Underlie Experimental Interpretations
Angular Resolved Photoemission experiments reveal the breakup of the Fermi surface in high Tc cuprate superconductor by forming pseudogap, starting at about 180K and reaching the isolated points for the superconducting state at 85K. That these points exist is strong evidence for the d-wave character of the superconductivity. The ability to see this detail was enabled by the theorist’s realization that one could characterize the energy dependence of the experimental data that made it possible to extract the information.
Theoretical efforts allow interpretations of photoemission to reveal pseudogap in superconducting cuprate and account for tip effect in STM observations.
DMS&E Theoretical Condensed Matter Physics CRA
Theory of ExperimentsTheory of Experiments
To advance frontiers in computational materials science through strong coupling with table-top experimental efforts as well as at BES user facilities to benchmark theoretical models and to guide experimental designs.
Theory vs. Experiment:silicon nanoclusters
Excited State Electronic StructureExcited State Electronic Structure
Large Facilities Science Table-top ScienceTheory and Computation
CMSN Cooperative Research TeamsCMSN Cooperative Research Teams
Current Teams
Under
DMS&E
Support
Excited State Electronic Structure and Response Functions: Louis, Rehr Magnetic Materials Bridging Basic and Applied Science: Stocks, Harmon Microstructural Effects on the Mechanics of Materials: Wolf, LeSar Fundamentals of Dirty Interfaces: From Atoms to Alloy Microstructures:
Rollett, Karma Predictive Capability for Strongly Correlated Electron Materials:
Scalettar, Pickett
Potential Additions
Multiscale Studies of Formation and Stability of Surface-based Nanostructures
The mission of the Computational Materials Science Network is to advance frontiers in computational materials science by assembling diverse sets of researchers committed to working together to solve relevant materials problems that require cooperation across organizational and disciplinary boundaries.
Collaborative Programs to Tackle Complex Grand ChallengesCollaborative Programs to Tackle Complex Grand Challenges
For more information on CMSN: http://www.phys.washington.edu/users/cmsn/
Materials Theory Institute (MTI)Materials Theory Institute (MTI) A visitors program designed to attract leading scientists with expertise
complementary to that available at the host institutions
Foster growth and expansion of theoretical science by catalyzing interdisciplinary interactions and collaborations
Format enables mobile, well focused, and highly interactive character research
Tackle a rich variety of the compelling and topical scientific problems that strengthen and expand the capabilities of the home institution
Regular workshops focused on the most urgent emerging topics to attract leading world scientists to advance the field and contribute to the creative and stimulating atmosphere of the Institute
Collaborative Programs to Tackle Complex Grand ChallengesCollaborative Programs to Tackle Complex Grand Challenges
DMS&E currently supports MTI projects at ANL and BNL
DMS&E recognizes many outstanding materials sciences issues could benefit considerably from high-end computing.
Access to high-end computer resources is a limiting factor for DMS&E researchers.
Reliability of time allocation over a period of several years is critical for optimum design of computation strategies.
Availability and Access to DMS&E Computational ResourcesAvailability and Access to DMS&E Computational Resources
DMS&E is pursuing options to• Seek further resource allocations within Office of
Science/ASCR• Leverage resources at other computer centers (e.g.,
NSF Centers)• Expand DOE Centers• Provide additional clusters
Software as Shared Research InfrastructureSoftware as Shared Research Infrastructure
Hyperdynamics and other multiple time scale techniques
Geometric Cluster Algorithm (GCA) for complex fluids simulation
Linear Expansion of Geometric Objects (LEGO)
Inverse band structure methods
Solving for many electron wave functions
Shared software and codes in CMSN Collaborative Research Teams
Current efforts in algorithm and technique development:
Compelling future needs to develop new algorithms and codes for general use at DOE’s leadership-class computing facilities
GCA yields several orders of magnitude efficiency improvement of complex fluids simulations
Bridging intermediate steps to incorporate the effects of rare but critical events into dynamic simulations
Expansion of Complex Solids enables wide search for lowest energy structures using search algorithms
New Avenues to ComputationNew Avenues to Computation
Spintronics – dissipationless spin currents
Quantum Computing – magnetic molecules & entangled states
x: current direction y: spin directionz: electric field
GaAsE
z
y
xAn equivalent to an “Ohm’s law” was discovered for quantum spintronics- Spin current can be induced by the electric field thru the spin-orbit coupling, and it can flow without dissipation!
kijkspinij EJ
Science 301, 1348 (2003)
►►Theoretical effort expanding on using spin as the Theoretical effort expanding on using spin as the mechanism of quantum computing and showing mechanism of quantum computing and showing the spin-orbit coupling can help rather than being the spin-orbit coupling can help rather than being only a loss mechanism.only a loss mechanism.
►►Starting a project based on using the spin Starting a project based on using the spin resonance of N isolated and positioned by an resonance of N isolated and positioned by an enclosing Cenclosing C6060 molecule. molecule.
Increase support for investigators at universities and labs – Increase support for investigators at universities and labs – particularly in nanoscience, correlated electrons systems, particularly in nanoscience, correlated electrons systems, defects in solids, electronically excited states defects in solids, electronically excited states
Provide additional computer clusters Provide additional computer clusters
Encourage theorists and computer scientists to work with Encourage theorists and computer scientists to work with facility users and other experimental effortsfacility users and other experimental efforts
Expand collaborative effortsExpand collaborative efforts
Enhance usage of high-end computers Enhance usage of high-end computers
Support develop new algorithms and codes for general useSupport develop new algorithms and codes for general use
Support research in new forms of computing (spintronics, Support research in new forms of computing (spintronics, quantum computing)quantum computing)
Outlooks for Theory and Computation in DMS&EOutlooks for Theory and Computation in DMS&E
The DMS&E FY2006 Budget includes an increase of $3M for theory and computation in nanoscience.
DMS&E Challenges and Strategies in Theory and ComputationDMS&E Challenges and Strategies in Theory and Computation
Challenges: Challenges: Build a “properly balanced” program under resource constraints
Maintain a coherent basic unity of theory, computation and experimental activities
Investment StrategiesInvestment Strategies Seek close coupling with nanoscience
Influence BES User Facilities to enhance support for theory and computation
Expand efforts through new funding opportunities (e.g., Hydrogen Fuel Initiative)
Contribute to and take advantage of BES strategic growth areas (i.e., ultrafast science, energy security research)
Thank You!Thank You!The report reinforces DMS&E investment
strategies and will guide our future theory and computation activities.
Recommended