RETROSPECTIVE

RETROSPECTIVE

Walter Kohn (1923–2016) Douglas J. Scalapinoa,1 and Robert Sugara

Walter Kohn, who died on April 19, 2016, once said “Physics isn’t what I do; it is what I am.” Indeed, Walter was a world-renowned physicist, winner of the 1960 Oliver E. Buckley Prize for his prediction of anomalies in the phonon spectrum in metals, the 1977 Davisson– Germer Prize with Nortan Lang for their studies of the inhomogeneous interacting electron gas at surfaces, and the 1991 Eugene Feenberg Medal for the development of density-functional theory. However, it was in Chemistry that Walter received the ultimate scientific recognition. The 1998 Nobel Prize in Chemistry was shared by Walter Kohn, “for his development of the density-functional theory,” and John A. Pople, “for his development of computational methods in quantum chemistry.” The Nobel Committee recognized Walter’s work in the 1960s with postdoctorates Pierre Hohenberg (Bell Labs) and Lu Sham (University of California, San Diego) in the development of the density-functional theory in which the properties of a many-electron system can be determined by using functionals of the spatially dependent electron density. This theory is among the most widely used methods for determining the electronic structure and properties of complex molecules and solids. Insight into this work, as well as the remarkable story of Walter’s introduction to physics at a segregated high school for Jews in Vienna and his subsequent escape from the Nazis by the Kindertransport, are recounted in an excellent article by Andrew Zangwill (1). Here, in this brief retrospective, we recount another aspect of Walter’s remarkable career: his time at the University of California, Santa Barbara (UCSB), beginning in 1979 when he became the first Director of the National Science Foundation’s (NSF) Institute for Theoretical Physics (ITP). In 1978 the UCSB proposal for an institute for theoretical physics was to go before the NSF Science Board. To obtain the approval of the Board it was essential that the institute have a distinguished director from outside of Santa Barbara. Walter was an ideal choice, given his scientific breadth and leadership ability. However, although the institute, now called the Kavli Institute for Theoretical Physics, is in its 37th year and internationally recognized, this was not initially the case. Walter, if he accepted, would be

Walter Kohn. Image courtesy of the Office of Public Affairs and Communications, University of California, Santa Barbara.

coming into a situation in which the outside community had mixed feelings about the establishment of such an institute. Fortunately, Walter accepted this challenge and in April 1978 the NSF Science Board approved funding for an initial period of five years, noting carefully that there was no certainty of continued support. So, in the fall of 1979 when Walter and his wife Mara arrived in Santa Barbara, the institute faced both doubts from the community and uncertainty of longterm NSF support. However, Walter’s ability to relate to the outside physics community and his judgment regarding both physics and people soon began to change things. He persuaded leading members of the physics community to serve on the ITP Advisory Board and to put tremendous effort into the development of ITP’s scientific programs. Under Walter’s leadership, a wide range of programs, proposed by the community and by members of the Advisory Board, were scheduled and successfully run. In addition, there were appointments of leading physicists as permanent members, including Frank Wilczek, J. Robert Schrieffer,

a Department of Physics, University of California, Santa Barbara, CA 93106 Author contributions: D.J.S. and R.S. wrote the paper. The authors declare no conflict of interest. 1 To whom correspondence should be addressed. Email: [email protected].

www.pnas.org/cgi/doi/10.1073/pnas.1609988113

PNAS | August 9, 2016 | vol. 113 | no. 32 | 8883–8884

and James Langer. Finally, Walter’s creation of a welcoming atmosphere made the institute a place where physicists, ranging from new doctorates to senior leaders of the field, wanted to visit. Walter set the direction and established the atmosphere that led to the Kavli Institute for Theoretical Physics becoming the major center it is today. After stepping down as Institute Director, Walter returned to teaching and research, mentoring additional doctorate students at UCSB. With Alan Heeger he directed and produced a film The Power of the Sun, telling the story of photovoltaics, the first solar panels, and where this technology could take us in the future. Walter worked with the Institut de la Vision in France to develop an optical corrective lens to treat macular degeneration. Walter and his wife Mara were active

in the campus community. Particularly memorable was their support of a concert in which Ullmann’s Quartet No. 3—composed while Ullmann was a prisoner at Theresienstadt concentration camp in 1943 and gassed at Auschwitz-Birkenau on October 18, 1944—was played. Walter explained his support of this concert, saying: “My parents, Salomon and Gittel Kohn, were in the Terezin (Theresienstadt) concentration camp with Viktor Ullmann. I would like to think that they heard some of his beautiful music.” Although over 37 years have passed since Walter became the first ITP director, his love of physics and his way of interacting with others lives on in Kohn Hall, which houses the Kavli Institute for Theoretical Physics, in the UCSB Physics department and the UCSB campus, to which he contributed so much.

1 Zangwill A (2014) The education of Walter Kohn and the creation of density-functional theory. Arch Hist Exact Sci 68(6):775–848.

8884 | www.pnas.org/cgi/doi/10.1073/pnas.1609988113

Scalapino and Sugar

Walter Kohn (1923-2016).

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