| Posted: June 23, 2010 |
Quantum simulations uncover hydrogen's phase transitions |
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(Nanowerk News) Hydrogen is the most abundant element in the universe and is a major component of giant planets such as Jupiter and Saturn.
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But not much is known about what happens to this abundant element under high-pressure conditions when it transforms from one state to another.
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Using quantum simulations, scientists at the Lawrence Livermore National Laboratory, the University of Illinois at Urbana-Champaign and the University of L'Aquia in Italy were able to uncover these phase transitions in the laboratory similar to how they would occur in the centers of giant planets.
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They discovered a first order phase transition, a discontinuity, in liquid hydrogen between a molecular state with low conductivity and a highly conductive atomic state. The critical point of the transition occurs at high temperatures, near 3100 degrees Fahrenheit and more than 1 million atmospheres of pressure.
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"This research sheds light on the properties of this ubiquitous element and may aid in efforts to understand the formation of planets," said LLNL's Eric Schwegler.
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The team used a variety of sophisticated quantum simulation approaches to examine the onset of molecular diassociation in hydrogen under high-pressure conditions. The simulations indicated there is a range of densities where the electrical conductivity of the fluid increases in a discontinuous fashion for temperatures below 3100 degrees Fahrenheit.
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There is a liquid-liquid-solid multiphase coexistence point in the hydrogen phase diagram that corresponds to the intersection of the liquid-liquid phase transition, according to Miguel Morales from the University of Illinois and lead author of a paper appearing online in the Proceedings of the National Academy of Sciences for the week of June 21-25.
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Other collaborators include Prof. David Ceperley from the University of Illinois at Urbana-Champaign, and Prof. Carlo Pierleoni from the University of L'Aquila. The work was funded in part by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program.
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