Kohn, Walter (1923-2016), an Austrian-born American physicist, made an important contribution to the applications of theoretical studies of molecules and chemical reactions. His work with the British chemist John Pople made it possible for scientists to analyze and predict chemical reactions in such diverse areas as the development of new drugs, propellants for aerospace, and the thinning of the ozone layer. Kohn developed a model called the density functional theory, which simplifies the mathematical description of the bonding between atoms that make up molecules. Kohn and Pople shared the 1998 Nobel Prize in chemistry. See Pople, John Anthony .
Kohn worked on an area of physics called quantum mechanics, a theory that explains the behavior of molecules in terms of the motions and energies of electrons (see Quantum mechanics ). Scientists use the theory to predict what will happen in chemical reactions. But because vast numbers of electrons may be involved in the reactions, the equations become too complicated to solve by traditional methods. In the mid-1960’s, Kohn devised the density functional theory, which deals with averages of the motions of electrons and so avoids trying to analyze the behavior of many individual electrons. This theory simplifies the calculations and gives scientists a practical way of solving such problems. The theory makes it possible to study the reactions of very large molecules. John Pople developed a computer program based on Kohn’s density functional theory that could quickly and accurately predict how different molecules would interact.
Kohn was born in Vienna, Austria, on March 9, 1923. His parents sent him to England in 1939 to escape the Nazi persecution of Jews (see Holocaust ). Kohn’s parents died in the Auschwitz concentration camp in Poland. From England, Kohn went to Canada. He studied at the University of Toronto and obtained a Ph.D. in physics at Harvard University in 1948. In 1960, he became a professor of physics at the University of California, San Diego. He founded the Institute for Theoretical Physics (now called the Kavli Institute for Theoretical Physics) at the University of California, Santa Barbara in 1979 and was its director from 1979 to 1984. Kohn died on April 19, 2016.
