Robert Walter Zwanzig (9 April 1928 – May 15, 2014) was an American theoretical physicist and chemist who made important contributions to the statistical mechanics of irreversible processes, protein folding, and the theory of liquids and gases.

Background

Zwanzig received his bachelor's degree from

Brooklyn Polytechnic Institute The New York University Tandon School of Engineering (commonly referred to as Tandon) is the engineering and applied sciences school of New York University. Tandon is the second oldest private engineering and technology school in the United St ...

in 1948 and his master's degree from 1950 at the

University of Southern California The University of Southern California (USC, SC, or Southern Cal) is a Private university, private research university in Los Angeles, California, United States. Founded in 1880 by Robert M. Widney, it is the oldest private research university in ...

. In 1952 he completed a doctorate in physical chemistry at

Caltech The California Institute of Technology (branded as Caltech) is a private university, private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small g ...

under the supervision of John G. Kirkwood. His thesis title was ''Quantum Hydrodynamics: a statistical mechanical theory of light scattering from simple non-polar fluids''. From 1951 to 1954 he worked as a post-doctoral researcher in theoretical chemistry at

Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...

, and from 1954 to 1958 he was an assistant professor in chemistry at Johns Hopkins University. From 1958 to 1966 he was a physical chemist at the National Bureau of Standards and from 1966 to 1979 he was a research professor at the Institute for Physical Science and Technology of the University of Maryland, where until 1988 he held he title of distinguished professor. From 1974 to 1975 he was a Fairchild Scholar at

. From 1988 onwards he was a researcher at the

National Institutes of Health The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in 1887 and is part of the United States Department of Health and Human Service ...

(National Institute of Diabetes and Digestive and Kidney Diseases) in

Bethesda, Maryland Bethesda () is an unincorporated, census-designated place in southern Montgomery County, Maryland, United States. Located just northwest of Washington, D.C., it is a major business and government center of the Washington metropolitan region ...

, where he was a Fogarty Scholar (1987–88) and later worked as a research scientist emeritus. One of his early works from 1954 is often cited as the first use of

free energy perturbation Free-energy perturbation (FEP) is a method based on statistical mechanics that is used in computational chemistry for computing free-energy differences from molecular dynamics or Metropolis Monte Carlo simulations. The FEP method was introduced ...

theory, and the resulting equation for the change in free energy is sometimes referred to as the Zwanzig equation. In the early 1960s he wrote some now classic works on the non-equilibrium thermodynamics and statistical mechanics of irreversible processes. He developed the projection operator formalism, which made it possible to derive irreversible transport equations (such as the

Boltzmann equation The Boltzmann equation or Boltzmann transport equation (BTE) describes the statistical behaviour of a thermodynamic system not in a state of equilibrium; it was devised by Ludwig Boltzmann in 1872.Encyclopaedia of Physics (2nd Edition), R. G ...

and other master equations) from reversible microscopic quantum mechanical dynamic equations. He drew heavily from the work of

Leon van Hove Leon, Léon (French) or León (Spanish) may refer to: Places Europe * León, Spain, capital city of the Province of León * Province of León, Spain * Kingdom of León, an independent state in the Iberian Peninsula from 910 to 1230 and again fro ...

. The projection operator formalism later found wide application and is now known as the Zwanzig-Mori formalism (also named after , who published similar results in 1965). An important result of the

Mori-Zwanzig formalism The Mori–Zwanzig formalism, named after the physicists and Robert Zwanzig, is a method of statistical physics. It allows the splitting of the dynamics of a system into a relevant and an irrelevant part using projection operators, which helps to ...

, the Nakajima-Zwanzig equation, bears his name and reflects the important contributions of Sadao Nakajima made around the same time. Together with Tsu-Wei Nee he derived a theory for the dielectric function and dielectric friction of dipolar liquids based on an extension of

Lars Onsager Lars Onsager (November 27, 1903 – October 5, 1976) was a Norwegian American physical chemist and theoretical physicist. He held the Gibbs Professorship of Theoretical Chemistry at Yale University. He was awarded the Nobel Prize in Chemist ...

's work. Later he worked on the

protein folding problem Protein structure prediction is the inference of the three-dimensional structure of a protein from its amino acid sequence—that is, the prediction of its secondary and tertiary structure from primary structure. Structure prediction is differe ...

among other things.

Awards and honors

He received many awards, including * the

Peter Debye Award The Peter Debye Award in Physical Chemistry is awarded annually by the American Chemical Society "to encourage and reward outstanding research in physical chemistry". The award is named after Peter Debye and granted without regard to age or natio ...

(1976), * the

Irving Langmuir Award The Irving Langmuir Prize in Chemical Physics is awarded annually, in even years by the American Chemical Society and in odd years by the American Physical Society. The award is meant to recognize and encourage outstanding interdisciplinary research ...

(1985), * the Joel H. Hildebrand Award (1994). He was a Fellow of the

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

and the

American Chemical Society The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all ...

Selected bibliography

*'' Nonequilibrium Statistical Mechanics'', Oxford University Press 2001

References

External links

Obituary from the University of Maryland
{{DEFAULTSORT:Zwanzig, Robert 1928 births 2014 deaths American physicists American physical chemists University of Southern California alumni Polytechnic Institute of New York University alumni California Institute of Technology alumni University of Maryland, College Park faculty