Walter Kohn

A banner on a lightpole at the University of California, Santa Barbara, commemorating Walter Kohn being awarded the Nobel Prize in Chemistry in 1998.

Walter Kohn (; March 9, 1923 – April 19, 2016) was an Austrian-American theoretical physicist and theoretical chemist. He was awarded, with John Pople, the Nobel Prize in Chemistry in 1998. The award recognized their contributions to understanding the electronic properties of materials. In particular, Kohn played the leading role in the development of density functional theory, which made it possible to calculate quantum mechanical electronic structure by equations involving the electronic density (rather than the many-body wavefunction). This computational simplification led to more accurate calculations on complex systems as well as many new insights, and it has become an essential tool for materials science, condensed-phase physics, and the chemical physics of atoms and molecules.

Early years in Canada Kohn arrived in England as part of the Kindertransport rescue operation immediately after the annexation of Austria by Hitler. He was from a Jewish family, and has written, "My feelings towards Austria, my native land, are – and will remain – very painful. They are dominated by my vivid recollections of 1 1/2 years as a Jewish boy under the Nazi regime, and by the subsequent murder of my parents, Salomon and Gittel Kohn, of other relatives and several teachers, during the Holocaust. ... I want to mention that I have a strong Jewish identity and – over the years – have been involved in several Jewish projects, such as the establishment of a strong program of Judaic Studies at the University of California, San Diego.".

Because he was an Austrian national, he was transferred to Canada in July 1940 after the outbreak of World War II. As a 17-year-old, Kohn traveled as part of a British convoy moving through U-boat-infested waters to Quebec City in Canada; and from there, by train, to a camp in Trois-Rivières. He was at first held in detention in a camp near Sherbrooke, Quebec. This camp, as well as others, provided a small number of educational facilities that Kohn used to the fullest, and he finally succeeded in entering the University of Toronto. As a German national, the future Nobel Laureate in Chemistry was not allowed to enter the chemistry building, so he opted for physics and mathematics. and remained until 1979. It was during this period, he, along with his student Chanchal Kumar Majumdar developed the Kohn–Majumdar theorem related to Fermi gas and its bound and unbound states. He then accepted the founding director's position at the new Institute for Theoretical Physics in Santa Barbara. He took his position as a professor in the Physics Department at the University of California, Santa Barbara in 1984; where he worked until the end of his life.

Kohn made significant contributions to semiconductor physics, which led to his award of the Oliver E. Buckley Prize by the American Physical Society. He was also awarded the Feenburg medal for his contributions to the many-body problem. His work on density functional theory was initiated during a visit to the in Paris, with Pierre Hohenberg, and was prompted by a consideration of alloy theory. The Hohenberg–Kohn theorem was further developed, in collaboration with Lu Jeu Sham, to produce the Kohn-Sham equations. The latter is the standard workhorse of modern materials science, and even used in quantum theories of plasmas.

In 1957, he relinquished his Canadian citizenship and became a naturalized citizen of the United States.

In 1963 Kohn became a Member of the American Academy of Arts and Sciences, a Member of the National Academy of Sciences in 1969, and a member of the American Philosophical Society in 1994. In 2011, he became an honorary member of the Austrian Academy of Sciences (ÖAW). He was also a Member of the International Academy of Quantum Molecular Science.

Death Kohn died on April 19, 2016, at his home in Santa Barbara, California from jaw cancer, at the age of 93. Austrian Decoration for Science and Art (1999) Grand Decoration of Honour in Silver with Star for Services to the Republic of Austria (2008) Harvard University awarded him an Honorary Doctor of Science (May 2012)

Selected publications W. Kohn, "An essay on condensed matter physics in the twentieth century," Reviews of Modern Physics, Vol. 71, No. 2, pp. S59–S77, Centenary 1999. APS W. Kohn, "Nobel Lecture: Electronic structure of matter — wave functions and density functionals," Reviews of Modern Physics, Vol. 71, No. 5, pp. 1253–1266 (1999). APS D. Jérome, T.M. Rice, and W. Kohn, "Excitonic Insulator," Physical Review, Vol. 158, No. 2, pp. 462–475 (1967). APS P. Hohenberg, and W. Kohn, "Inhomogeneous Electron Gas," Physical Review, Vol. 136, No. 3B, pp. B864–B871 (1964). APS W. Kohn, and L. J. Sham, "Self-Consistent Equations Including Exchange and Correlation Effects," Physical Review, Vol. 140, No. 4A, pp. A1133–A1138 (1965). APS W. Kohn, and J. M. Luttinger, "New Mechanism for Superconductivity," Physical Review Letters, Vol. 15, No. 12, pp. 524–526 (1965). APS W. Kohn, "Theory of the Insulating State," Physical Review, Vol. 133, No. 1A, pp. A171–A181 (1964). APS W. Kohn, "Cyclotron Resonance and de Haas-van Alphen Oscillations of an Interacting Electron Gas," Physical Review, Vol. 123, pp. 1242–1244 (1961). APS