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AIP’s The Journal of Chemical Physics Spotlights Nobel Laureate Roald Hoffmann

APR 19, 2012

Renowned scientist and colleagues discuss their recent series of papers on dense hydrogen

Melville, NY, April 19, 2012The Journal of Chemical Physics (JCP) is putting the spotlight on Nobel Laureate Roald Hoffmann, Cornell University’s Frank H.T. Rhodes Professor in Humane Letters and professor emeritus of chemistry, and his recent work on hydrogen.

The behavior of hydrogen under very high pressure was the subject of a series of four papers, recently published in JCP, that were written by Hoffmann and his Cornell colleagues, including chemist Vanessa Labet and physicist Neil Ashcroft.

“Roald Hoffmann is one of the nation’s leading theoretical chemists,” says JCP Editor Marsha Lester. “His series of papers presents a rare and detailed look at the evolution of scientific understanding of a complex and important topic.”

Hydrogen, the lightest and most abundant element in the universe, is normally a gas; but under extreme pressure, such as in the interior of giant gas planets, hydrogen’s properties change, and it can act like a metal. Under these conditions, so-called dense hydrogen becomes “the subject of intense experimental research and an important problem” for physicists and chemists to solve, says Hoffmann. His colleague Neil Ashcroft predicts that dense hydrogen will be a superconductor, perhaps a superfluid.

Materials under pressure are “like a bunch of sardines in a can, or people in a Tokyo subway at rush hour,” notes Hoffmann. “You have to get closer together. That’s the only imperative.” It is known that the distance between hydrogen molecules, which comprise two hydrogen atoms, must shrink under increasing pressure. However, it is not certain how the pressure increase affects the distance between the two atoms in each molecule, or under what conditions the diatomic arrangement disintegrates and a monatomic solid structure forms. Hoffmann and his colleagues examine these outstanding questions from both a physical and chemical perspective.

The question of how hydrogen behaves at high densities is interesting “not just because [hydrogen] appears in the planets and the suns and so on, but it’s an utterly fundamental system,” notes Ashcroft.

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