Robert Ghormley Parr (September 22, 1921 – March 27, 2017) was an American

theoretical chemist Theoretical chemistry is the branch of chemistry which develops theoretical generalizations that are part of the theoretical arsenal of modern chemistry: for example, the concepts of chemical bonding, chemical reaction, valence, the surface ...

who was a Professor of Chemistry at the

University of North Carolina at Chapel Hill A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States ...

Career

Parr received an A. B. degree ''magna cum laude'' from Brown University in 1942, and then entered the

University of Minnesota The University of Minnesota, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public land-grant research university in the Twin Cities of Minneapolis and Saint Paul, Minnesota, United States. ...

, receiving a Ph.D. in

physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistica ...

in 1947. He joined the faculty at Minnesota upon receiving his Ph.D. and remained there one year. In 1948 he moved to the

Carnegie Institute of Technology Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania. One of its predecessors was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools; it became the Carnegie Institute of Technology ...

(now Carnegie Mellon University) in

Pittsburgh Pittsburgh ( ) is a city in the Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County. It is the most populous city in both Allegheny County and Western Pennsylvania, the second-most populous city in Pennsylva ...

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

, becoming a full professor in 1957. In 1962 he moved to

Johns Hopkins University Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hemisphere. It consi ...

Baltimore, Maryland Baltimore ( , locally: or ) is the List of municipalities in Maryland, most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic (United States), Mid-Atlantic, and List of United States cities by popula ...

, and in 1974 to the

, where he received appointment to an endowed professorship in 1990 and where he last taught.

Achievements and awards

Working with DuPont chemist

Rudolph Pariser Rudolph Pariser (born December 8, 1923) is a physical and polymer chemist. He was born in Harbin, China to merchant parents, Ludwig Jacob Pariser and Lia Rubinstein. He attended the Von Hindenburg Schule in Harbin, an American Missionary School ...

, Parr developed a method of computing approximate

molecular orbital In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of findin ...

s for

pi electron In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals ...

systems, published in 1953. Since an identical procedure was derived by John A. Pople the same year, it is generally referred to as the

Pariser–Parr–Pople method In molecular physics, the Pariser–Parr–Pople method applies Computational Chemistry#Semiempirical methods, semi-empirical quantum mechanical methods to the quantitative prediction of electronic structures and spectra, in molecules of interest i ...

or PPP method. The PPP method differed from existing structural chemistry thinking (which advocated ''maximum overlap principle'') by advancing the concept of ''zero differential overlap approximation''. By 1978 Parr had realized that

density functional theory Density-functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body ...

(DFT) would be extremely useful in quantitative calculations of chemical and biological systems, especially those with high molecular weights. In 1988 Parr,

Weitao Yang Weitao Yang (; born March 31, 1961) is a Chinese-born American chemist who is the Philip Handler Professor of Chemistry at Duke University. His main contributions to chemistry include density functional theory development, and its applications t ...

and Chengteh Lee produced an improved DFT method which could approximate the correlation energy of systems. The LYP (for Lee-Yang-Parr) functional theory is now one of the most-often cited papers in the chemical literature. In 1963 Parr published ''Quantum Theory of Molecular Electronic Structure'', one of the first books to apply quantum theory to chemical systems. In 1989 he and Yang published ''Density Functional Theory of Atoms and Molecules'', now considered the basic textbook on DFT.

Awards and honors

*Member of the

International Academy of Quantum Molecular Science The International Academy of Quantum Molecular Science (IAQMS) is an international scientific learned society covering all applications of quantum theory to chemistry and chemical physics. It was created in Menton in 1967. The founding members we ...

*1967 - Co-founded (with 4 others) the

*1994 - Winner of

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 ...

's Irving Langmuir Award in Chemical Physics *2004 - winner of

United States National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, 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 Nati ...

Award in Chemical Sciences *2009 - winner of American Chemical Society's Award in Theoretical Chemistry

References

{{DEFAULTSORT:Parr, Robert 1921 births 2017 deaths Brown University alumni University of Minnesota alumni American physical chemists Theoretical chemists Carnegie Mellon University faculty Members of the United States National Academy of Sciences Members of the International Academy of Quantum Molecular Science Foreign Fellows of the Indian National Science Academy Computational chemists Fellows of the American Physical Society