The British poet William Blake saw a universe in a grain of sand and
eternity in an hour. Physicist Arthur Freeman also sees a universe in
tiny things -- a universe of opportunity for materials science. Using
modern quantum physics, Freeman explores the interactions among electrons
and nuclei that give rise to the fundamental properties of matter. And
fortunately for him, access to the supercomputing resources of the Alliance
ensures that it won't take an eternity to make the calculations.
Freeman is the Morrison Professor of Physics at Northwestern University in
Evanston, Illinois. He's a leader in the emerging field of computational
materials science, which rests on the principle that the properties of
matter arise from interactions among atoms that can be rendered
mathematically. By calculating the distribution of electrons in a material
across a spectrum of energies -- its electronic structure -- it is possible
to predict how well the material conducts heat or electricity, how ductile
or brittle it is, how it responds to magnetic fields, and other fundamental
properties.
Freeman is best known for his theoretical advances in understanding the
magnetic properties of thin films and surfaces. His calculations revealed,
for example, that thin films -- those less than one micron (one millionth
of a meter) thick -- can actually have stronger magnetic properties than
the material in bulk form. Other researchers are working to parlay some of
his discoveries into higher-density data storage technologies such as
compact disks. For his work in magnetic materials, Freeman received the
First Materials Research Society Medal in 1990 as well as the First
International Union of Pure and Applied Physics (IUPAP) Award in Magnetism
in 1991. Freeman is also the founding editor and editor-in-chief of the
Journal of Magnetism and Magnetic Materials.
Recently, Freeman and two post-doctoral students from his group at
Northwestern -- Oleg Kontsevoi and Oleg Mryasov --
used the SGI/CRAY Origin2000 at NCSA to study atomic-scale defects that
develop in all solid materials. The defects are important because they
determine the strength of a material -- its ability to resist mechanical
stress. When materials undergo stress, dislocations-- shifts in the
position of atoms in the crystal -- allow the material to deform
plastically instead of break. The Northwestern team simulated different
types of dislocations. One type, called edge dislocations,can be
imagined as extra rows of atoms squeezed between adjacent rows. The other
type they studied, called screw dislocations,happens when rows of
atoms are twisted with respect to each other into a pattern resembling a
spiral.
