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{{Short description|Ab initio quantum chemistry software package}}
{{Infobox software
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| logo                   = [[File: MOLPRO logo.jpg|200px|Molpro chemistry programme]] 
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| developer              = H.-J. Werner and P. J. Knowles
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| latest release version = {{wikidata|property|preferred|references|edit@end|P348|P548=Q2804309}}
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| genre                  = [[Computational chemistry]]
| license                = academic
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'''MOLPRO''' is a software package used for accurate ''[[Ab initio quantum chemistry methods|ab initio]]'' [[quantum chemistry]] calculations.<ref>{{cite book|title=Computational Chemistry|url=https://archive.org/details/computationalche00youn_371|url-access=limited| first1=David |last1=Young|publisher=Wiley-Interscience|year= 2001|chapter=Appendix A. A.2.6 MOLPRO|page=[https://archive.org/details/computationalche00youn_371/page/n401 338]|isbn=978-0-471-33368-5}}</ref> It is developed by Peter Knowles at [[Cardiff University]] and Hans-Joachim Werner at [[Universität Stuttgart]] in collaboration with other authors.

The emphasis in the program is on highly accurate computations, with extensive treatment of the [[Electronic correlation|electron correlation problem]] through the [[multireference configuration interaction]], [[coupled cluster]] and associated methods. Integral-direct local electron correlation methods reduce the increase of the computational cost with molecular size. Accurate ab initio calculations can then be performed for larger molecules. With new explicitly correlated methods the [[Basis set (chemistry)|basis set]] limit can be very closely approached.

==History==
Molpro was designed and maintained by Wilfried Meyer and [[Peter Pulay]] in the late 1960s. At that moment, Pulay developed the first analytical gradient code called [[Hartree–Fock method|Hartree-Fock (HF)]],<ref>{{cite journal|last1=Pulay|first1=Peter|title=Ab initio calculation of force constants and equilibrium geometries in polyatomic molecules|journal=Molecular Physics|date=1969|volume=17|issue=2|pages=197–204|doi=10.1080/00268976900100941|bibcode=1969MolPh..17..197P}}</ref><ref>{{cite journal|last1=Pulay|first1=Peter|title=Ab initio calculation of force constants and equilibrium geometries in polyatomic molecules. II. Force constants of water|journal=Molecular Physics|date=1970|volume=18|issue=4|pages=473–480|doi=10.1080/00268977000100541|bibcode=1970MolPh..18..473P}}</ref><ref>{{cite journal|last1=Pulay|first1=Peter|title=Ab initio calculation of force constants and equilibrium geometries III. Second-row hydrides|journal=Molecular Physics|date=1971|volume=21|issue=2|pages=329–339|doi=10.1080/00268977100101451|bibcode=1971MolPh..21..329P}}</ref> and Meyer researched his PNO-CEPA (pseudo-natural orbital coupled-electron pair approximation) methods.<ref>{{cite journal|last1=Meyer|first1=Wilfried|title=PNO-CI and CEPA studies of electron correlation effects. I. Configuration expansion by means of nonorthogonal orbitals, and application to the ground state and ionized states of methane|journal= Journal of Chemical Physics|date=1973|volume=58|issue=3|pages=1017–1035|doi=10.1063/1.1679283|url=https://www.researchgate.net/publication/234222102|bibcode=1973JChPh..58.1017M}}</ref><ref>{{cite journal|last1=Meyer|first1=Wilfried|title=PNO-CI and CEPA studies of electron correlation effects II. Potential curves and dipole moment functions of the OH radical|journal=Theoretica Chimica Acta|date=1974|volume=35|issue=4|pages=277–292|doi=10.1007/BF00548478|s2cid=92652572 }}</ref> In 1980, Werner and Meyer developed [[Multi-configurational self-consistent field|a new state-averaged, quadratically convergent (MC-SCF) method]], which provided geometry optimization for [[Multireference configuration interaction|multireference cases]].<ref name=' mcscf ' >{{cite journal|last1=Werner|first1=Hans-Joachim|last2=Meyer|first2=Wilfried|title=A quadratically convergent MCSCF method for the simultaneous optimization of several states|journal=The Journal of Chemical Physics|date=1981|volume=74|issue=10|pages=5794|doi=10.1063/1.440892|bibcode=1981JChPh..74.5794W|doi-access=free}}</ref>  By the same year, the first internally contracted multireference configuration interaction (IC-MRCI) program was developed by Werner and Reinsch.<ref>{{cite journal|last1=Werner|first1=Hans-Joachim|last2=Reinsch|first2=Ernst-Albrecht|title=The self-consistent electron pairs method for multiconfiguration reference state functions|journal=The Journal of Chemical Physics|date=1982|volume=76|issue=6|pages=3144|doi=10.1063/1.443357|bibcode=1982JChPh..76.3144W}}</ref> About four years later (1984), Werner and Knowles developed on a new generation program called [[Multi-configurational self-consistent field#Complete Active Space SCF|CASSCF (complete active space SCF)]]. This new CASSCF program combined fast orbital optimization algorithms<ref name=' mcscf ' /> with [[Full configuration interaction|determinant-based full CI codes]],<ref>{{cite journal|last1=Knowles|first1=P.J.|last2=Handy|first2=N.C.|title=A new determinant-based full configuration interaction method|journal=Chemical Physics Letters|date=November 1984|volume=111|issue=4–5|pages=315–321|doi=10.1016/0009-2614(84)85513-X|bibcode=1984CPL...111..315K}}</ref> and additional, more general, unitary group configuration interaction (CI) codes. This resulted in the quadratically convergent MCSCF/CASSCF code called MULTI,<ref>{{cite journal|last1=Werner|first1=Hans-Joachim|last2=Knowles|first2=Peter J.|title=A second order multiconfiguration SCF procedure with optimum convergence|journal=The Journal of Chemical Physics|date=1985|volume=82|issue=11|pages=5053|doi=10.1063/1.448627|url=https://www.researchgate.net/publication/239343024|bibcode=1985JChPh..82.5053W}}</ref><ref>{{cite journal|last1=Knowles|first1=Peter J.|last2=Werner|first2=Hans-Joachim|title=An efficient second-order MC SCF method for long configuration expansions|journal=Chemical Physics Letters|date=April 1985|volume=115|issue=3|pages=259–267|doi=10.1016/0009-2614(85)80025-7|url=http://www.citeulike.org/user/krapnik/article/6334798|bibcode=1985CPL...115..259K|url-access=subscription}}</ref>  which allowed modals to be optimized a weighted energy average of several states, and is capable of treating both completely general configuration expansions. In fact, this method is still available today. In addition to these organizational developments, Knowles and Werner started to cooperate on a new, more efficient, IC-MRCI method.<ref>{{cite journal|last1=Werner|first1=Hans-Joachim|last2=Knowles|first2=Peter J.|title=An efficient internally contracted multiconfiguration–reference configuration interaction method|journal=The Journal of Chemical Physics|date=1988|volume=89|issue=9|pages=5803|doi=10.1063/1.455556|bibcode=1988JChPh..89.5803W}}</ref><ref>{{cite journal|last1=Knowles|first1=Peter J.|last2=Werner|first2=Hans-Joachim|title=An efficient method for the evaluation of coupling coefficients in configuration interaction calculations|journal=Chemical Physics Letters|date=April 1988|volume=145|issue=6|pages=514–522|doi=10.1016/0009-2614(88)87412-8|bibcode=1988CPL...145..514K}}</ref> Extensions for accurate treatments of excited states became possible through a new IC-MRCI method.<ref>{{cite journal|last1=Knowles|first1=Peter J.|last2=Werner|first2=Hans-Joachim|title=Internally contracted multiconfiguration-reference configuration interaction calculations for excited states|journal= Theoretica Chimica Acta|date=1992|volume=84|issue=1|pages=95–103|doi=10.1007/BF01117405|s2cid=96830841 }}</ref> In brief, the present IC-MRCI will be described as [[Multireference configuration interaction|MRCI]]. These recently developed MCSCF and MRCI methods resulted in the basis of the modern Molpro. In the following years, a number of new programs were added. Analytic energy gradients can be evaluated with [[Coupled cluster|coupled-cluster calculations]], [[Density functional theory|density functional theory (DFT)]], as well as many other programs. These structural changes make the code more modular and easier to use and maintain, and also reduces the probability of input error.<ref>{{cite journal|last1=Werner|first1=Hans-Joachim|last2=Knowles|first2=Peter J.|last3=Knizia|first3=Gerald|last4=Manby|first4=Frederick R.|last5=Schutz|first5=Martin|title=Molpro: a general-purposequantum chemistry programpackage|journal=WIREs Computational Molecular Science|date=2011|volume=2|issue=2|pages=242–253|doi=10.1002/wcms.82|s2cid=94868368 }}</ref>

==See also==
{{columns-list|colwidth=22em|
* [[Quantemol | Quantemol Electron Collisions]]
* [[CP2K]]
* [[GAMESS]]
* [[Gaussian (software)]]
* [[MOLCAS]]
* [[MPQC]]
* [[NWChem]]
* [[PQS (chemical)|PQS]]
* [[PSI (computational chemistry)|Psi4]]
* [[Q-Chem]]
* [[TeraChem]]
* [[TURBOMOLE]]
* [[Grace (plotting tool)|Grace]]
* [[Global Arrays]]
* [[Quantum chemistry computer programs]]
* [[ORCA (quantum chemistry program)]]
}}

==References==
<references/>

== External links ==
* {{Official website}}

{{Chemistry software}}

[[Category:Computational chemistry software]]