Project Highlights
Researchers Delve Deeply into Liquid Water Structure with Blue Gene/L
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Turns out the structure of water may not be crystal clear.
Until recently, researchers believed that liquid water molecules clustered in tetrahedral groups of four - small pyramids with triangular bases, formed when each water molecule connects to four others. Then, in 2004, Stanford Linear Accelerator Center researchers asserted they found structures of rings and chains instead. Another team at Lawrence Berkeley Laboratory conducted similar experiments and reaffirmed the old tetrahedral model.
Resolving this issue is not a simple matter. Experiments are extremely difficult to do. A strictly theoretical approach can't solve it. So a team of researchers led by Giulia Galli, Professor of Chemistry at the University of California, Davis and Principal Investigator (http://angstrom.ucdavis.edu/), turned to computational modeling for the answer. Team members include Francois Gygi, Professor of Applied Science at UC Davis and Co-Investigator; David Prendergast and Jeffrey Grossman at UC Berkeley; and Eric Schwegler, a physicist at Lawrence Livermore National Laboratory.
A grant of 2.5 million hours of computer processor time has been awarded to them through the U.S. Department of Energy's INCITE (Innovative and Novel Computational Impact on Theory and Experiment) program. The team is running calculations on the IBM Blue Gene/L supercomputers at Argonne National Laboratory and IBM's T.J. Watson Research Laboratory. The researchers are going through trillions of quantum calculations to determine what structure water should have according to basic principles. These calculations require months of computer time and numerous, different ab-initio molecular dynamics runs. Both structural and spectroscopic results obtained by Galli's team so far confirm the tetrahedral model, as reported in a recent paper published by Galli and Prendergast ("X-ray absorption spectra of water from first principles calculations," D. Prendergast and G.Galli, Phys.Rev.Lett. 96, 215502, 2006), but more work needs to be done to understand the fine details.
The team is also interested in how water behaves when it is squeezed into tiny spaces, such as a carbon nanotube. To this end, they are creating computational tools to simulate the electronic and structural properties of confined water at the nanoscale as it comes into contact with materials such as silicon carbide and graphite sheets. This work will help researchers predict how the properties of a liquid might be altered in a nanoscale confinement. Their findings may have implications for using nanotechnology to build very small devices that can handle liquids. The calculations are carried out with the Qbox code (http://eslab.ucdavis.edu/), written and developed by one of the team members, Prof. F. Gygi. Earlier this year, this code demonstrated a Gordon Bell Award winning performance of 207 teraflops (TF) on another BG/L machine at Lawrence Livermore National Laboratory.
(Sources: UCDavis News & Information; Science & Technology, Lawrence Livermore National Laboratory; Science Journal)
Contact
Giulia Galli
University of California – Davis
More Information
http://angstrom.ucdavis.edu/
http://www.news.ucdavis.edu/search/news_detail.lasso?id=7637
http://www.post-gazette.com/pg/06069/668422.stm
http://www.llnl.gov/str/JanFeb06/Schwegler.html
