Small-scale modeling yields big dividends

Some of the most well known work coming from the Lab deals with computational modeling at the smallest level. Providing invaluable data to many projects involving simulations at the microscopic scale is the Quantum Simulations Group (QSG) in the Physics and Applied Technologies directorate, led by physicist Giulia Galli.

Harnessing the Lab’s unique computational power and the JEEP code developed by team collaborator Francois Gygi from Computation, Galli and her team conduct simulations at the microscopic level using the laws of quantum mechanics.

"There is no doubt that using this Lab’s computational power is a unique opportunity," said Galli. "In no other place in the world could we do quantum simulations for systems as large as we can deal with here, and so closely represent true experimental conditions and approach actual experimental results."

The team’s current work explores the quantum behavior of various fluids under high pressure, behavior of DNA in water, and the properties of complex surfaces and nanostructures.

"Our goal, and what we are excited to actually see, is technical and theoretical developments closer and closer to actual experiment, by using computational modeling," Galli said.

Galli will be discussing her team’s work in quantum molecular dynamics on Science Day, March 21 at 2:30 p.m. in the Bldg. 123 auditorium. Her talk, "Quantum Simulations of Condensed Matter Systems," addresses "how the physical properties of water and hydrogen are modified at high temperature and pressure, the interaction of some organic molecules with water, and how structural and electronic properties of selected semiconductors are modified at the nanoscale."

In addition to talks by Lab scientists and engineers on the theme of supercomputing, the Science Day celebration will highlight research from across the Lab in a poster session. (For more information, see the Website at http://stars.llnl.gov/ScienceDay/ .)

Galli said that the QSG team’s research currently focuses on the "investigation of systems and processes relevant to condensed matter physics, physical chemistry and material science, using electronic structure calculations and quantum simulations.

"We interact with many other departments at the Lab," Galli explained, as the QSG can offer other departments a kind of virtual laboratory for quantum level work. "In short, quantum simulations can provide information that complements real laboratories and mathematical theories.

"Most of our projects are LDRD funded and involve collaborative efforts with several other directorates. In particular we have a very fruitful collaboration with Biology and Biotechnology Research on computational biology, and a Basic Energy Science (BES) funded collaboration with Chemistry and Materials Science on the properties of surfaces and nanostructures."

Furthermore, the study of the physical properties of various materials and their reactions under extreme conditions – which are often not possible in true experimentation – are critical to the Stockpile Stewardship Program and its research in the behavior of the nation’s nuclear weapons.

Galli came to the Lab three years ago, after seven years at the Swiss Institute for Technology and postdoctoral fellowships at the University of Illinois at Champaign Urbana and IBM Zurich.

For more information on Galli’s research with the Quantum Simulations Group, see http://www-phys.llnl.gov/Research/qsg/index.html or http:// www.llnl.gov/str/Gygi.html .