Leonard Kleinman

(July 25, 1933– )

Biography of Leonard Kleinman

I was born on July 25, 1933, in New York City to Leo and Ann Kleinman, and spent my first eight years in Mount Vernon, NY when we moved to Los Angeles in July 1940. I got my BA from UCLA in February 1955 and an MS in June 1956 on the Hughes Masters Program. (*Len was inducted into Phi Beta Kappa at UCLA.–*Mel Oakes) This entailed working 26 hours a weak at Hughes Aircraft and is where I first became interested in solid state physics. In September 1956, I went to Berkeley. On July 3, 1957, I married Faye Millar in Santa Monica. We were married until she passed away on April 2, 1999. We adopted two infant children, Julie in June 1966 and Paul in January 1969.

When I asked Charles Kittel to be my thesis advisor, he told me that experimentalists are happier than theorists but, nevertheless, he accepted me as his student. However, I ended up working with his postdoc, Jim Phillips. Jim had spent two years as a postdoc at Bell Labs working with Conyers Herring, the inventor of the orthogonalized plane wave (OPW) method for performing electronic structure calculations. There, he had developed an empirical pseudopotential and wanted to develop a first principles one. (A pseudopotential is a weak potential which joins smoothly to the actual atomic potential outside the core and produces correct wave functions outside the core and correct eigenvalues. It greatly facilitates computation.) Jim had me make atomic calculations using the supposedly first principles pseudopotentials in the literature. When the results ran from poor to complete nonsense, I asked Jim why we couldn’t mimic the OPW, i.e. orthogonalize an arbitrary smooth function to the core functions and plug this into the Schrödinger equation and take those terms containing the core functions as the pseudopotential. Jim said he had tried it and it could not be done and to go and calculate some more. I was young and naive and believed if Jim couldn’t do it and Herring couldn’t and all the other people who must have tried couldn’t, then I couldn’t either. Two days later, Jim informed me that he had tried again and succeeded. After publishing four papers with Jim, I got my PhD in January 1960 and got an offer from the Hughes Research Lab in Malibu at $13,100. I had not applied for any postdoc positions so was surprised when I received a phone call from Morrel Cohen offering me a postdoc at the University of Chicago at $6,500. My father never understood why I would turn down a $13,100 job for one paying $6,500.

I left Chicago after 16 months because Faye threatened divorce if I didn’t. The Hyde Park area around the university was particularly miserable and dangerous back then. I spent three years at the University of Pennsylvania, three at the University of Southern California, and came to Austin in August 1967 after U.T. made me an offer I couldn’t refuse. In 1980, I received a manuscript by Hamman, Schluter, and Chiang (HSC) to review for *Physical Review Letters*. I realized that their norm conserving form of pseudopotential had some advantages over our pseudopotential. I also realized that it could be made relativisticly correct by using the Dirac equation. Approximating the Dirac equation by the Schrödinger equation causes errors of order (Z/137)2, i. e., 45% for uranium with Z = 92. When the Dirac pseudopotential is used in the Schrödinger equation, the error is only of order 1/137 so this was quite important for calculations on systems with heavy elements. The HSC pseudopotential required the integration of n(n + 1)/2 matrix elements where n is the number of plane waves in the expansion. In some cases, n can be 10,000 or more, so it was an important improvement when, in 1982, I showed how to factorize the HSC pseudopotential, reducing number of integrations to n. Two other seminal papers are on self consistent, electronic structure calculations of thin films to study surface properties in 1972 and on the hybridized exchange energy density functional in 1990. Most of my work has been involved with calculations of the magnetic, electric and physical properties of a wide range of condensed matter systems. Since I have not performed any computer calculations since completing my thesis, I must thank my students, postdocs, and research associates, without whose work almost all of my 260 publications would have failed to see the light of day. I also want to thank my colleagues and the staff for making the U. T. Physics Department such an enjoyable place to work.

Len Kleinman, senior picture, Los Angeles High School, yearbook, *Blue and White*, 1951.

Jim Phillips, Morrel Cohen, Leonard Kleinman

Leonard Kleinman, University of Texas at Austin

Leonard Kleinman

Leonard Kleinman

Leonard Kleinman, RLM Building, UT