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The description of the behavior of large collections of atoms and molecules requires a combination of efforts: computer simulation methods and clever applications of statistical mechanics theory. Not many chemists master both.
During the past two decades, however, work by Hans C. Andersen, David Mulvane Ehrsam & Edward Curtis Franklin Professor of Chemistry at Stanford University, has made it possible for the area of chemistry known as molecular dynamics to explode. On the foundation laid by Andersen's work, scientists have been able to examine the properties and interactions of gases, liquids, and solids.
The early molecular dynamics strategies, based on Newton's equations of motion and statistical mechanical principles, were developed in the 1950s and '60s. But these simulations didn't realistically mimic experimental conditions. In the methodology available at the time, the energy, volume, and number of particles in a molecular dynamics simulation were kept constant. But that's not usually representative of experimental conditions, where systems are typically maintained at constant temperature and pressure. For example, the nucleation of liquid materials into the solid phase can involve large volume changes.
In 1980, Andersen published a paper in the Journal of Chemical Physics that offered a solution to that problem. By altering and making additions to the equations of motion, Andersen showed how to perform molecular dynamics simulations for systems based on constant pressure and temperature. The work allowed molecular dynamics to explode as a discipline.
"It is rare that a single paper has such a profound and lasting impact," says Michele Parrinello, chemistry professor at the Swiss Federal Institute of Technology, Zurich, and a pioneer in molecular dynamics.
Andersen's peers note that his contributions to theoretical chemistry extend beyond this earlier work, including his modeling studies of liquids, amorphous materials, crystal nucleation, and phase transitions. "The breadth of Hans Andersen's contributions to theoretical chemistry is truly remarkable," says David Chandler, chemistry professor at the University of California, Berkeley.
Andersen was born in 1941 in Brooklyn, N.Y. He received a bachelor's degree in chemistry in 1962 and a Ph.D. in 1966, both from Massachusetts Institute of Technology. He spent three years at Harvard University as a junior fellow, then went to Stanford, where he has been ever since. At Stanford, Andersen has served in various directorial roles at the university's Center for Materials Research. He was chair of the chemistry department from 2002 to 2005.
His numerous awards include a Guggenheim Fellowship in 1976 and the ACS Joel Henry Hildebrand Award in the Theoretical & Experimental Chemistry of Liquids in 1988. He has been a fellow of the American Physical Society since 1984, the American Association for the Advancement of Science since 1991, and the American Academy of Arts & Sciences since 1992. He has also been a member of the National Academy of Sciences since 1992.
Andersen has served as chair of the ACS Division of Physical Chemistry and on the editorial boards of several journals, including the Journal of Chemical Physics.
The award address will be presented before the Division of Physical Chemistry.—Elizabeth Wilson