# Presentation: 139909

## BESAC Subcommittee on Theory and Computation

***Co-Chairs***
- Bruce Harmon – Ames Lab and Iowa State University
- Kate Kirby – ITAMP, Harvard Smithsonian Center for Astrophysics
- Bill McCurdy – University of California, Davis, and Berkeley Lab

## Charge to the Subcommittee

***The subcommittee is to identify current and emerging challenges and opportunities for theoretical research within the scientific mission of Basic Energy Sciences, with particular attention paid to how computing will be employed to enable that research.  A primary purpose of the subcommittee is to identify those investments that are necessary to ensure that theoretical research will have maximum impact in the areas of importance to Basic Energy Sciences, and to guarantee that  BES researchers will be able to exploit the entire spectrum of computational tools, including the leadership class facilities contemplated by the Office of Science.***

## Timeline for preparation of the full subcommittee report

- February 22, 2004:  First meeting of the subcommittee, prior to the February meeting of BESAC.
- April 17-18, 2004: Subcommittee meeting in Chicago to take testimony and discuss preliminary ideas and findings
- June 4, 2004: “Letter” report of the committee, delivered to John Hemminger and Pat Dehmer, for discussion at the August 5,6 meeting of BESAC.
- July 30, 2004: First draft “extended outline” delivered to entire subcommittee on Theory and Computing in the Basic Energy Sciences
*August 5 & 6, 2004: BESAC discussion of the preliminary report.*
*Fall meeting of BESAC:  Proposed final draft of the full report to be delivered to BESAC for its evaluation.*
*End of January, 2005: Final bound report to be delivered to the Office of Science and BES *

## Subcommittee Members

- Roberto Car, Princeton U.
- Peter Cummings, Vanderbilt U.
- Jim Davenport, BNL
- Thom Dunning, UT/ORNL
- Bruce Garrett, PNNL
- Chris Greene, U. of Colorado
- Bruce Harmon, Ames Lab
- Rajiv Kalia, USC
- Kate Kirby, Harvard-Smithsonian Center for Astrophysics
- Walter Kohn, UC-Santa Barbara

- Carl Lineberger, U. of Colorado
- Bill McCurdy, UC- Davis/LBNL
- Mike Norman, ANL
- Larry Rahn, Sandia/Livermore
- Tony Rollett, Carnegie Mellon
- Douglas Tobias, UC-Irvine
- Stan Williams, Hewlett-Packard
- Margaret Wright, Courant Institute, NY

## Opportunities for Discovery: Theory and Computation in Basic Energy Sciences

- Subcommittee on Theory and Computation
- of the Basic Energy Sciences Advisory Committee
- U.S. Department of Energy

## Executive Summary

**I.****	****A Confluence of Scientific Opportunities: Why Invest Now ****in Theory and Computation in the Basic Energy Sciences? **
- A.	Dramatic Progress in Theory and Modeling in Chemistry and 	Materials Sciences
- B.	New Scientific Frontiers
- C.	New Experimental Facilities
- D.	New Computational Capabilities
**II.****	****BES Community Input and Assessment**
- A.	Subcommittee Expertise
- B.	Testimony of the Theory Community
- C.	Questions Solicited of the BES Community
- D.	A Consensus Observation: The Unity of Theory and 	Computation in the Basic Energy Sciences

## III.	Emerging Themes in BES: Complexity and Control

- A.	Opportunities and Challenges in Complex Systems
- B.	Opportunities and Challenges in Quantum Control
- Opportunities and Challenges in Control of Complex Systems
**IV.****	****Connecting Theory with Experiment at the DOE Facilities: Accelerating Discoveries and Furthering Understanding**
- A Major Theme Expressed by Experimentalists and Theorists in the Basic Energy Sciences
**V.****	****The Resources Essential for Success in the BES Theory Enterprise**
- A.	The Full Spectrum of Computational Resources
- B.	Supporting New Styles of Theory and Computation in the BES Portfolio: Scientific Codes As Shared Instruments
- The Human Resources: Training Future Generations of Theorists
**VI.****	****Findings and Recommendations**

## I.	A Confluence of Scientific Opportunities: Why Invest Now in Theory and Computation in the Basic Energy Sciences?

- Striking recent scientific successes of theory and modeling
- The appearance of specific new scientific frontiers
- The development and construction of new experimental facilities
- The ongoing increase of computational capability, including the promise of new leadership-scale computational facilities.

## Dramatic Progress in Theory and Computation

- Density functional theory (DFT) has transformed theoretical chemistry, surface and materials science
- Large-scale classical molecular dynamics has been able to treat motion of  > a million atoms
- Discrete grid and wave-packet methods for treating atoms/molecules, e.g. in intense fields
- A range of electronic structure methods have evolved:  coupled cluster, MBPT, QMC
- First-principles spin dynamics elucidated mechanism of giant magnetoresistance and spintronic devices
- Dynamical mean field theory (DMFT) successful in describing strongly correlated electronic states
*Ab Initio* molecular dynamics (Car-Parinello) treats motion of atoms and changes in electronic structure

## New Scientific Frontiers

- Nanoscience
- Ultrafast Chemistry and Physics
- Biomaterials and Biomimetic Systems
- Coherent Control
- Control of Quantum Coherence
- Spintronics

## New Experimental Facilities

- Existing “Light Sources”: APS (Argonne), ALS (LBL), and NSLS (Brookhaven), together with the new Linac Coherent Light Source under construction at SLAC, have created a growing wave of new experiments in chemistry, physics and materials science;
- Construction of the Spallation Neutron Source at ORNL (sched. Completion 2006);
- Five Nanoscale Science Research Centers under design or construction;
- Needed:  an overall strategy and increased support for theoretical research to guide and respond to the experiments at these facilities.

## New Computational Capabilities

- Desktop workstations -- rapid growth in microprocessor speed (Moore’s Law);
- Cluster computing -- tens or hundreds of processors linked together, and run by a single research group or department;  have helped to ready many disciplines within BES for massively parallel computing;
- Large-scale computing facilities -- operated by DOE and NSF (and others).  Centers at NERSC (LBL), ORNL, and Argonne; new facility at PNNL; leadership-class facility at ORNL;
- BES research -- a major user of these facilities;
- BES community has demonstrated READINESS

## II.   BES Community Input:  Obtaining Testimony from the Community

- Open meeting, April 17, 2004 in Chicago area; 16+ invited talks, plus panel discussions
- Website established to collect input: _[https://besac.nersc.gov](https://besac.nersc.gov/)__ _
- E-mails inviting input to website, or to co-chairs directly, to DAMOP, DCP, DMP, DCMP of APS
- Announcement inviting input on ACS Division of Physical Chemistry home page

## Questions asked of BES Community

- In your field, what are the major scientific challenges?
- In your area, do theory and computational science drive progress and/or partner with experiment?
- How might progress in your field impact other areas within BES?
- Are computing resources (hardware & software) a limiting factor in your field?
- Would support for development of new algorithms for high-end computer architectures be important?
- Are there opportunities in your area to assemble interdisciplinary teams for attacking large problems?

## Consensus Observation:  The Unity of Theory and Computation in BES

- Theory and computation should be viewed as a unity, not as competing parts of the BES portfolio;
- Theory enterprise in BES is heterogeneous, with respect to scientific problems,  research group size and computational resources required;
- Ensuring the highest quality scientific return requires the complete spectrum of theory activity (from the single-PI groups to the large, interdisciplinary teams), coupled with access to appropriate computational resources.