Rutgers physicists tackle plutonium complexities

NEW BRUNSWICK/PISCATAWAY, N.J. - Three physicists, members of the Center for Materials Theory in the Rutgers department of physics and astronomy, have devised a new method which opens the way to the prediction of the physical properties of plutonium. This development may be important for the long-term storage of plutonium, an issue of worldwide concern.

In a paper appearing in the April 11, 2001 issue of the journal Nature, Rutgers' Sergej Y. Savrasov, post-doctoral associate, Gabriel Kotliar, professor of physics, and Elihu Abrahams, director of the Center for Materials Theory (Bernard Serin Professor of Physics, Emeritus), present a novel electronic structure method for predicting stability changes in plutonium, potentially a landmark achievement in solid state physics.

Plutonium is regarded even by scientists as a complex and mysterious element, rarely occurring in nature, and made artificially for the first time in 1940. "Just as water has phases - liquid, solid and gaseous - so does plutonium," explains Kotliar. "In plutonium there are many more solid phases, ranging from a dense alpha phase to a much more extended delta phase. Being able to predict the stability of these phases tells us that we now have a better understanding of the electronic properties of this fascinating metal."

"While the search for answers about plutonium phases has generally been through experimental methods, we employed analytic and computer calculations to predict changes in the structure of the solid states of plutonium," said Kotliar. "We felt a strong need for theoretical methods that are accurate. This element is far too difficult to handle for extensive experimental procedures in many laboratories and the use of theoretical methods is mandatory if we are to deal with its solid properties over very long time scales, which are not accessible experimentally."

In developing its new method, the team employed Rutgers' High-Performance Computing Cluster, a computational grid comprising more than 80 computer processors configured as a distributed resource. They can now predict volume and stability changes in plutonium and they are gaining insights into where and when the transition between alpha and delta phases fits in the scheme of things.

"We are dealing with an extremely delicate balance between the two phases, and which one wins and when this happens is information that is necessary to design the long range storage of this important material," added Kotliar.

The paper in Nature is titled "Correlated Electrons in delta Plutonium within a Dynamical Mean Field Picture" by S. Y. Savrasov, G. Kotliar, E. Abrahams, Department of Physics and Astronomy and Center for Materials Theory, Rutgers University, Piscataway, NJ. Journalists registered with Nature can view the paper at http://press.nature.com/ or they may contact Joseph Blumberg at [email protected].

The work presented in the paper was supported by the Department of Energy Division of Basic Energy Sciences and by Los Alamos National Laboratory.

EDITOR'S NOTE: This is a revised version containing a corrected quote by Dr. Gabriel Kotliar. He can be reached for interviews at (732) 445-4331 or by e-mail, [email protected].

Sergej Savrasov may also be reached for interviews at (732) 445-4381 or by e-mail, [email protected].