- Person
- Walter Kohn
- Lived
- 1923–2016
- Field
- Theoretical physics
- From
- Austrian-American
The story
Walter Kohn was born in Vienna in 1923 into a Jewish family. After the Nazi annexation of Austria he was expelled from his school, and in August 1939 he escaped to England on the Kindertransport. His parents, who could not leave, were murdered in the Holocaust. Interned as an enemy alien and sent to camps in Canada, he studied mathematics and physics with fellow internees and went on to the University of Toronto and Harvard, where he earned his PhD in physics in 1948.
The laws of quantum mechanics that govern atoms and molecules were known by the late 1920s, but they were almost impossible to apply to real chemistry. The standard approach had to follow the motion of every electron in a molecule, and the mathematics grows explosively as the number of electrons rises.
In 1963, on a sabbatical in Paris, Kohn asked whether that detail was really necessary. Could everything about a system be worked out from its electron density, the average number of electrons at each point in space? With the young physicist Pierre Hohenberg he proved in 1964 that the answer is yes. In 1965, with his postdoctoral fellow Lu Jeu Sham in San Diego, he produced the Kohn–Sham equations, which turn the problem into one that computers can actually solve. Together these papers founded density functional theory, known as DFT.
It took many researchers several decades to make the method accurate enough for routine use. In awarding Kohn the 1998 Nobel Prize in Chemistry, shared with John Pople, the Royal Swedish Academy of Sciences said that the simplicity of the method makes it possible to study very large molecules, for example to explain how enzymatic reactions occur, and that it was by then one of the most widely used methods in quantum chemistry.
DFT calculations now run in laboratories and companies around the world. Chemists, physicists and engineers use them to predict the shapes of molecules, follow chemical reactions step by step and screen new materials on a computer before making them, from catalysts and battery materials to semiconductors and solar cell materials. Kohn himself later championed solar energy, serving as executive producer of a 2005 documentary, The Power of the Sun.
Why it matters
Density functional theory lets scientists design and test new medicines, materials and energy technologies on computers, saving years of laboratory trial and error.
About Walter Kohn
Viennese refugee who escaped on the Kindertransport and created density functional theory, the method scientists now use to calculate how molecules and materials behave. Nobel Prize 1998.
Sources
- Press release: The Nobel Prize in Chemistry 1998 NobelPrize.org
- Walter Kohn, Biographical NobelPrize.org
- Density functional theory Wikipedia
- Walter Kohn Wikipedia
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