Editing Computational chemistry (section)

== History ==
Building on the founding discoveries and theories in the [[history of quantum mechanics]], the first theoretical calculations in chemistry were those of [[Walter Heitler]] and [[Fritz London]] in 1927, using [[valence bond theory]].<ref>{{Cite journal |last1=Heitler |first1=W. |last2=London |first2=F. |date=1927-06-01 |title=Wechselwirkung neutraler Atome und homöopolare Bindung nach der Quantenmechanik |url=https://doi.org/10.1007/BF01397394 |journal=Zeitschrift für Physik |language=de |volume=44 |issue=6 |pages=455–472 |doi=10.1007/BF01397394 |bibcode=1927ZPhy...44..455H |s2cid=119739102 |issn=0044-3328|url-access=subscription }}</ref> The books that were influential in the early development of computational quantum chemistry include [[Linus Pauling]] and [[Edgar Bright Wilson|E. Bright Wilson]]'s 1935 ''Introduction to Quantum Mechanics – with Applications to Chemistry'',<ref>{{Cite book |last1=Pauling |first1=Linus |author1-link= Linus Pauling | author2-link=Edgar Bright Wilson|title=Introduction to quantum mechanics: with applications to chemistry |last2=Wilson |first2=Edgar Bright |date=1985 |publisher=Dover publications |isbn=978-0-486-64871-2 |location=New York}}</ref> [[Henry Eyring (chemist)|Eyring]], Walter and Kimball's 1944 ''Quantum Chemistry'',<ref>{{Cite book |last1=Eyring |first1=Henry |author1-link=Henry Eyring (chemist) |title=Quantum chemistry |last2=Walter |first2=John |last3=Kimball |first3=George E. |date=1967 |publisher=Wiley |isbn=978-0-471-24981-8 |edition=14th print |location=New York}}</ref> Heitler's 1945 ''Elementary Wave Mechanics – with Applications to Quantum Chemistry'',<ref>{{Cite book |last=Heitler |first=W. |title=Elementary Wave Mechanics with Applications to Quantum Chemistry |date=1956-01-01 |publisher=Oxford University Press |isbn=978-0-19-851103-8 |edition=2 |language=English}}</ref> and later [[Charles Coulson|Coulson]]'s 1952 textbook ''Valence'', each of which served as primary references for chemists in the decades to follow.<ref>{{Cite book |last1=Coulson |first1=Charles Alfred |author1-link=Charles Coulson |title=Coulson's valence |last2=McWeeny |first2=Roy |date=1991 |publisher=Oxford university press |isbn=978-0-19-855145-4 |edition=3rd |series=Oxford science publications |location=Oxford New York Toronto [etc.]}}</ref>

With the development of efficient computer technology in the 1940s, the solutions of elaborate [[wave equation]]s for complex [[atom]]ic systems began to be a realizable objective.  In the early 1950s, the first semi-empirical atomic orbital calculations were performed. Theoretical chemists became extensive users of the early digital computers. One significant advancement was marked by Clemens C. J. Roothaan's 1951 paper in the Reviews of Modern Physics.<ref name="Roothaan-1951">{{Cite journal |last=Roothaan |first=C. C. J. |date=1951-04-01 |title=New Developments in Molecular Orbital Theory |url=https://link.aps.org/doi/10.1103/RevModPhys.23.69 |journal=Reviews of Modern Physics |volume=23 |issue=2 |pages=69–89 |doi=10.1103/RevModPhys.23.69|bibcode=1951RvMP...23...69R }}</ref><ref name="Ruedenberg-1954">{{Cite journal |last=Ruedenberg |first=Klaus |date=1954-11-01 |title=Free-Electron Network Model for Conjugated Systems. V. Energies and Electron Distributions in the FE MO Model and in the LCAO MO Model |url=https://doi.org/10.1063/1.1739935 |journal=The Journal of Chemical Physics |volume=22 |issue=11 |pages=1878–1894 |doi=10.1063/1.1739935 |bibcode=1954JChPh..22.1878R |issn=0021-9606|url-access=subscription }}</ref> This paper focused largely on the "LCAO MO" approach (Linear Combination of Atomic Orbitals Molecular Orbitals). For many years, it was the second-most cited paper in that journal.<ref name="Roothaan-1951" /><ref name="Ruedenberg-1954" />   A very detailed account of such use in the United Kingdom is given by Smith and Sutcliffe.<ref>{{cite journal |last1= Smith |first1= S. J. |last2= Sutcliffe |first2= B. T. |title= The development of Computational Chemistry in the United Kingdom |journal= Reviews in Computational Chemistry |volume= 10 |pages= 271–316 |year= 1997}}</ref> The first ''ab initio'' [[Hartree–Fock method]] calculations on diatomic molecules were performed in 1956 at MIT, using a [[Basis set (chemistry)|basis set]] of [[Slater orbital]]s.<ref>{{Cite journal |last1=Boys |first1=S. F. |last2=Cook |first2=G. B. |last3=Reeves |first3=C. M. |last4=Shavitt |first4=I. |date=1956-12-01 |orig-date=1 December 1956 |title=Automatic Fundamental Calculations of Molecular Structure |url=https://www.nature.com/articles/1781207a0 |journal=Nature |language=en |volume=178 |issue=4544 |pages=1207–1209 |doi=10.1038/1781207a0 |bibcode=1956Natur.178.1207B |s2cid=4218995 |issn=1476-4687|url-access=subscription }}</ref> For diatomic molecules, a systematic study using a minimum basis set and the first calculation with a larger basis set were published by Ransil and Nesbet respectively in 1960.<ref>{{cite book |last= Schaefer |first =Henry F. III |title= The electronic structure of atoms and molecules |url= https://archive.org/details/electronicstruct0000scha |url-access= registration |publisher= Addison-Wesley Publishing Co. |year= 1972 |page= [https://archive.org/details/electronicstruct0000scha/page/146 146] |location= Reading, Massachusetts}}</ref> The first polyatomic calculations using [[Gaussian orbital]]s were performed in the late 1950s. The first [[configuration interaction]] calculations were performed in Cambridge on the [[EDSAC]] computer in the 1950s using Gaussian orbitals by [[Francis Boys|Boys]] and coworkers.<ref>{{cite journal |last1= Boys |first1= S. F. |author1-link= Francis Boys |last2=Cook |first2= G. B. |last3= Reeves |first3= C. M. |last4= Shavitt |first4= I. |title= Automatic fundamental calculations of molecular structure |journal= Nature |volume= 178 |issue= 2 |page= 1207 |year= 1956 |doi= 10.1038/1781207a0 |bibcode=1956Natur.178.1207B|s2cid= 4218995 }}</ref> By 1971, when a bibliography of ''ab initio'' calculations was published,<ref>{{cite book |last1= Richards |first1 =W. G. |last2=Walker |first2= T. E. H. |author3=Hinkley R. K. |title= A bibliography of ''ab initio'' molecular wave functions |publisher= Clarendon Press |year= 1971 |location= Oxford}}</ref> the largest molecules included were [[naphthalene]] and [[azulene]].<ref>{{Cite journal|last=Preuss|first= H. |year=1968|journal=International Journal of Quantum Chemistry|volume=2|issue= 5 |page= 651|bibcode= 1968IJQC....2..651P |doi= 10.1002/qua.560020506 |title= DasSCF-MO-P(LCGO)-Verfahren und seine Varianten}}</ref><ref>{{cite journal |last1= Buenker |first1= R. J. |last2= Peyerimhoff |first2= S. D. |year=1969|journal=Chemical Physics Letters|volume=3|issue= 1 |page= 37|doi=10.1016/0009-2614(69)80014-X|title=Ab initio SCF calculations for azulene and naphthalene|bibcode= 1969CPL.....3...37B}}</ref> Abstracts of many earlier developments in ''ab initio'' theory have been published by Schaefer.<ref>{{cite book |last= Schaefer |first =Henry F. III |title= Quantum Chemistry |publisher= Clarendon Press |year= 1984 |location= Oxford}}</ref>

In 1964, [[Hückel method]] calculations (using a simple [[linear combination of atomic orbitals]] (LCAO) method to determine electron energies of molecular orbitals of π electrons in conjugated hydrocarbon systems) of molecules, ranging in complexity from [[butadiene]] and [[benzene]] to [[ovalene]], were generated on computers at Berkeley and Oxford.<ref>{{cite book |last1= Streitwieser |first1= A. |last2=Brauman |first2= J. I. |last3=Coulson |first3= C. A. |author-link3= Charles Coulson |title= Supplementary Tables of Molecular Orbital Calculations |publisher =Pergamon Press |year= 1965 |location= Oxford}}</ref> These empirical methods were replaced in the 1960s by [[Semi-empirical quantum chemistry method|semi-empirical methods]] such as [[CNDO/2|CNDO]].<ref>{{cite book |last1= Pople |first1= John A. |author-link= John Pople |last2=Beveridge |first2= David L. |title= Approximate Molecular Orbital Theory |publisher= McGraw Hill |year= 1970 |location= New York}}</ref>

In the early 1970s, efficient ''ab initio'' computer programs such as ATMOL, [[Gaussian (software)|Gaussian]], IBMOL, and POLYAYTOM, began to be used to speed ''ab initio'' calculations of molecular orbitals.<ref name="Ma-2022">{{Cite journal |last=Ma |first=Xiaoyue |date=2022-12-01 |title=Development of Computational Chemistry and Application of Computational Methods |journal=Journal of Physics: Conference Series |volume=2386 |issue=1 |pages=012005 |doi=10.1088/1742-6596/2386/1/012005 |bibcode=2022JPhCS2386a2005M |issn=1742-6588|doi-access=free }}</ref> Of these four programs, only Gaussian, now vastly expanded, is still in use, but many other programs are now in use.<ref name="Ma-2022" />  At the same time, the methods of [[molecular mechanics]], such as MM2 [[Force field (chemistry)|force field]], were developed, primarily by [[Norman Allinger]].<ref>{{cite journal |last= Allinger |first= Norman |author-link= Norman Allinger
 |title= Conformational analysis. 130. MM2. A hydrocarbon force field utilizing V1 and V2 torsional terms
 |journal= Journal of the American Chemical Society |volume= 99 |pages= 8127–8134 |year= 1977
 |doi= 10.1021/ja00467a001 |issue= 25|bibcode= 1977JAChS..99.8127A }}</ref>

One of the first mentions of the term ''computational chemistry'' can be found in the 1970 book ''Computers and Their Role in the Physical Sciences'' by Sidney Fernbach and Abraham Haskell Taub, where they state "It seems, therefore, that 'computational chemistry' can finally be more and more of a reality."<ref>{{cite book |last1= Fernbach |first1= Sidney |last2=Taub |first2= Abraham Haskell |title= Computers and Their Role in the Physical Sciences |publisher= Routledge |year= 1970 |isbn= 978-0-677-14030-8}}</ref> During the 1970s, widely different methods began to be seen as part of a new emerging discipline of ''computational chemistry''.<ref>{{Cite book | editor1= Kenny B. Lipkowitz|editor2= Donald B. Boyd |chapter-url=https://onlinelibrary.wiley.com/doi/10.1002/9780470125786.fmatter |title=Reviews in Computational Chemistry |chapter=vol 1, preface |doi=10.1002/9780470125786 |year=1990 |volume=1 |publisher=Wiley |isbn=978-0-470-12578-6 }}</ref> The ''[[Journal of Computational Chemistry]]'' was first published in 1980.

Computational chemistry has featured in several Nobel Prize awards, most notably in 1998 and 2013. [[Walter Kohn]], "for his development of the density-functional theory", and [[John Pople]], "for his development of computational methods in quantum chemistry", received the 1998 [[Nobel Prize]] in Chemistry.<ref>{{cite web|url=https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1998/index.html|title=The Nobel Prize in Chemistry 1998}}</ref> [[Martin Karplus]], [[Michael Levitt (biophysicist)|Michael Levitt]] and [[Arieh Warshel]] received the 2013 [[Nobel Prize]] in Chemistry for "the development of multiscale models for complex chemical systems".<ref name="bio">{{cite press release
 |title= The Nobel Prize in Chemistry 2013
 |publisher= Royal Swedish Academy of Sciences
 |date= October 9, 2013
 |url= https://www.nobelprize.org/nobel_prizes/chemistry/laureates/2013/press.html
 |access-date= October 9, 2013}}</ref>