Editing Robert Parr

{{Short description|American theoretical chemist (1921–2017)}}
{{other people}}
{{Refimprove|date=February 2013}}
[[File:Robert_Parr.jpg|thumb|Portrait of Robert Ghormley Parr]]
'''Robert Ghormley Parr''' (September 22, 1921 &ndash; March 27, 2017) was an American [[theoretical chemistry|theoretical chemist]] who was a professor of chemistry at the [[University of North Carolina at Chapel Hill]].<ref name="AyersYang2017">{{cite journal|last1=Ayers|first1=Paul|last2=Yang|first2=Weitao|title=Robert G. Parr (1921-2017)|journal=Angewandte Chemie International Edition|volume=56|issue=36|year=2017|pages=10639|issn=1433-7851|doi=10.1002/anie.201705477|pmid=28776903|doi-access=free}}</ref><ref>{{cite web | url=http://www.iaqms.org/members/parr.php | title=His International Academy of Quantum Molecular Science page | access-date=2017-09-12}}</ref><ref>{{cite web | url=http://www.legacy.com/obituaries/heraldsun/obituary.aspx?pid=184743785 | title=Robert Parr Obituary - Chapel Hill, NC - The Herald Sun | website=[[Legacy.com]] | access-date=2017-09-12}}</ref>

==Career==
Parr received an A. B. [[academic degree|degree]] ''magna cum laude'' from [[Brown University]] in 1942, and then entered the [[University of Minnesota]], receiving a Ph.D. in [[physical chemistry]] 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]] (now [[Carnegie Mellon University]]) in [[Pittsburgh]], [[Pennsylvania]], becoming a full professor in 1957. In 1962 he moved to [[Johns Hopkins University]] in [[Baltimore, Maryland]], and in 1974 to the [[University of North Carolina at Chapel Hill]], where he received appointment to an endowed professorship in 1990 and where he last taught.

==Achievements and awards==
Working with [[DuPont]] chemist [[Rudolph Pariser]], Parr developed a method of computing approximate [[molecular orbital]]s for [[pi electron]] systems, published in 1953. Since an identical procedure was derived by [[John Pople|John A. Pople]] the same year, it is generally referred to as the [[Pariser–Parr–Pople method]] 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]] (DFT) would be extremely useful in quantitative calculations of chemical and biological systems, especially those with high molecular weights.  In 1988 Parr, [[Weitao Yang]] 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 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]]<ref name=CEN2009/>
*1967 - Co-founded (with 4 others) the [[International Academy of Quantum Molecular Science]]<ref name=CEN2009/>
*1994 - Winner of [[American Chemical Society]]'s [[Irving Langmuir Award]] in Chemical Physics<ref name=CEN2009/><ref>{{cite web | url=https://www.acs.org/content/acs/en/funding-and-awards/awards/national/bytopic/irving-langmuir-award-in-chemical-physics.html | title=Irving Langmuir Award in Chemical Physics | publisher=[[American Chemical Society]] | access-date=2017-09-12}}</ref>
*2004 - winner of [[United States National Academy of Sciences]] Award in Chemical Sciences<ref name=CEN2009/>
*2009 - winner of American Chemical Society's Award in Theoretical Chemistry<ref name=CEN2009>{{cite journal|journal=Chemical & Engineering News|volume=87|issue=3|year=2009|pages=72–76|issn=0009-2347|doi=10.1021/cen-v087n003.p072|title=2009 ACS National Award Winners|doi-access=free}}</ref>

==References==
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{{DEFAULTSORT:Parr, Robert}}
[[Category:1921 births]]
[[Category:2017 deaths]]
[[Category:Brown University alumni]]
[[Category:University of Minnesota alumni]]
[[Category:American physical chemists]]
[[Category:American theoretical chemists]]
[[Category:Carnegie Mellon University faculty]]
[[Category:Members of the United States National Academy of Sciences]]
[[Category:Members of the International Academy of Quantum Molecular Science]]
[[Category:Foreign fellows of the Indian National Science Academy]]
[[Category:American computational chemists]]
[[Category:Fellows of the American Physical Society]]