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By Gary Stiehr, May 27, 2011 11:33 pm

Carbon dating is used to help determine the age of artifacts, dinosaur bones and so on.  Carbon-14’s nearly 6,000-year half-life is a key reason why this method of calculating age is thought to be accurate.  Until recently, however, scientist didn’t understand why carbon-14’s half life was so long when other light atomic nuclei can have a half-life of minutes or seconds.  Nuclear physicists at Iowa State University used the Jaguar supercomputer at ORNL to understand this mystery.  According to an article on physorg.com:

The reason involves the strong three-nucleon forces (a nucleon is either a neutron or a proton) within each carbon-14 nucleus. It’s all about the simultaneous interactions among any three nucleons and the resulting influence on the decay of carbon-14. And it’s no easy task to simulate those interactions.

To do this simulation required 30,000,000 CPU hours on the Jaguar supercomputer, which has a peak performance of 2.3 Petaflops.  The calculation required dealing with a 30 billion x 30 billion matrix with 30 trillion non-zero elements.  The article mentions that there was the need to adapt the code to scale properly.  It also says that this was “six months of work pressed into three months of time.”  At 30,000,000 CPU hours over three months, that would require 13,889 processors utilized at 100% efficiency.

A related previous post about Jaguar: 147,000 Processors Used for Atom-by-Atom Simulation of Nanoscale Transistor

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By Gary Stiehr, January 26, 2009 11:09 pm

First-principle simulations have been used to directly determine the miscibility of helium (gold balls) in dense metallic hydrogen (white balls) under the extreme conditions that are present in the interiors of the Jovian planets. Illustration by Kwei-Yu Chu

Physicists at Lawrence Livermore National Laboratory and the University of Illinois at Urbana-Champaign have done First-Principles Molecular Dynamics (FPMD) simulations on LLNL’s high performance computing systems to “determine the equation of state of the hydrogen-helium system at extremely high temperatures (4,000-10,000 degrees Kelvin), similar to what would be found in the interior of Saturn and Jupiter.”   Read more here.