Editing PSI (computational chemistry)

{{Infobox software
| logo =
| name = Psi4
| developer = The Psi4 Project
| operating_system = [[Linux]], [[Microsoft Windows]], [[macOS|Mac OS X]]
| latest release version = Psi4 1.8
| latest release date = {{Start date and age|2023|5|11}}<ref>{{cite web |date=May 11, 2023 |access-date=September 2, 2023 |title=v1.8 — May 2023 |url=https://psicode.org/posts/v18/}}</ref>
| programming language  = [[C++]], [[Python (programming language)|Python]]
| genre = [[Computational chemistry]]
| license = [[GPL]]
| website = http://www.psicode.org
}}
'''Psi''' is an [[Ab initio quantum chemistry methods|ab initio]] [[computational chemistry]] package originally written by the research group of [[Henry F. Schaefer, III]] ([[University of Georgia]]). Utilizing Psi, one can perform a calculation on a [[molecular]] system with various kinds of methods such as [[Hartree-Fock method|Hartree-Fock]], [[Post-Hartree–Fock]] electron correlation methods, and [[density functional theory]].<ref name=Homepage /><ref name="PirhadiSunseri2016" /> The program can compute energies, optimize molecular geometries, and compute vibrational frequencies.<ref name=Homepage /><ref name="PirhadiSunseri2016" /> The major part of the program is written in [[C++]], while [[Python (programming language)|Python]] [[API]] is also available, which allows users to perform complex computations or automate tasks easily.<ref name=Homepage /><ref name="TurneySimmonett2012"/><ref name="ParrishBurns2017" /><ref name="Smith2020" />

'''Psi4''' is the latest release of the program package - it is [[Open-source software|open source]], released as [[free software|free]] under the [[LGPL-3.0|LGPL3]]  through [[GitHub]]. Primary development of '''Psi4''' is currently performed by the research groups of [[David Sherrill]] ([[Georgia Institute of Technology|Georgia Tech]]), T. Daniel Crawford ([[Virginia Tech]]), Francesco Evangelista ([[Emory University]]), and [[Henry F. Schaefer, III]] ([[University of Georgia]]), with substantial contributions by  Justin Turney ([[University of Georgia]]), Andy Simmonett ([[NIH]]), and Rollin King ([[Bethel University (Minnesota)|Bethel University]]).<ref name=Homepage /><ref name="TurneySimmonett2012"/><ref name="ParrishBurns2017"/><ref name="Smith2020"/> '''Psi4''' is available on Linux releases such as Fedora and Ubuntu.

==Features==

The basic capabilities of Psi are concentrated around the following methods<ref name=Homepage /> of [[quantum chemistry]]:
* [[Hartree–Fock method]]
* [[Density functional theory]]
* [[Møller–Plesset perturbation theory]]
* [[Coupled cluster]]
* [[Multi-configurational self-consistent field#Complete active space SCF|CASSCF]]
* [[Multireference configuration interaction]] methods
* [[Symmetry-adapted perturbation theory]]

Several methods are available for computing excited electronic states, including [[configuration interaction]] singles (CIS), the [[random phase approximation]] (RPA), [[time-dependent density functional theory]] (TD-DFT), and equation-of-motion coupled cluster (EOM-CCSD).<ref name=Homepage />

'''Psi4''' has introduced the density-fitting approximation in many portions of the code, leading to faster computations and reduced I/O requirements.<ref name=Homepage /><ref name="TurneySimmonett2012"/><ref name="ParrishBurns2017" />

'''Psi4''' is the preferred quantum chemistry backend for the OpenFermion project, which seeks to perform quantum chemistry computations on quantum computers.<ref name="Kahn2017"/>

In '''Psi4''' 1.4,<ref name="Smith2020" /> the program was adapted to facilitate high-throughput workflows and can be connected to [https://www.brianqc.com BrianQC] to speed up calculations for [[Hartree–Fock method|Hartree-Fock]] and [[Density functional theory]] methods.

==See also==
{{Portal|Free and open-source software}}
* [[List of quantum chemistry and solid-state physics software]]

==References==
{{Reflist|refs=
<ref name=Homepage>{{cite web|url=http://www.psicode.org/|publisher=The PSI4 Project|title=Psi4: Open-Source Quantum Chemistry|access-date=2017-07-06}}</ref>
<ref name="PirhadiSunseri2016">{{cite journal|last1=Pirhadi|first1=Somayeh|last2=Sunseri|first2=Jocelyn|last3=Koes|first3=David Ryan|title=Open source molecular modeling|journal=Journal of Molecular Graphics and Modelling|volume=69|year=2016|pages=127–143|issn=1093-3263|doi=10.1016/j.jmgm.2016.07.008|pmid=27631126|pmc=5037051}}</ref>
<ref name="TurneySimmonett2012">{{cite journal|last1=Turney|first1=Justin M.|last2=Simmonett|first2=Andrew C.|last3=Parrish|first3=Robert M.|last4=Hohenstein|first4=Edward G.|last5=Evangelista|first5=Francesco A.|last6=Fermann|first6=Justin T.|last7=Mintz|first7=Benjamin J.|last8=Burns|first8=Lori A.|last9=Wilke|first9=Jeremiah J.|last10=Abrams|first10=Micah L.|last11=Russ|first11=Nicholas J.|last12=Leininger|first12=Matthew L.|last13=Janssen|first13=Curtis L.|last14=Seidl|first14=Edward T.|last15=Allen|first15=Wesley D.|last16=Schaefer|first16=Henry F.|last17=King|first17=Rollin A.|last18=Valeev|first18=Edward F.|last19=Sherrill|first19=C. David|last20=Crawford|first20=T. Daniel|title=Psi4: an open-source ab initio electronic structure program|journal=Wiley Interdisciplinary Reviews: Computational Molecular Science|volume=2|issue=4|year=2012|pages=556–565|issn=1759-0876|doi=10.1002/wcms.93|s2cid=57101524 }}</ref>
<ref name="ParrishBurns2017">{{cite journal|last1=Parrish|first1=Robert M.|last2=Burns|first2=Lori A.|last3=Smith|first3=Daniel G. A.|last4=Simmonett|first4=Andrew C.|last5=DePrince|first5=A. Eugene|last6=Hohenstein|first6=Edward G.|last7=Bozkaya|first7=Uğur|last8=Sokolov|first8=Alexander Yu.|last9=Di Remigio|first9=Roberto|last10=Richard|first10=Ryan M.|last11=Gonthier|first11=Jérôme F.|last12=James|first12=Andrew M.|last13=McAlexander|first13=Harley R.|last14=Kumar|first14=Ashutosh|last15=Saitow|first15=Masaaki|last16=Wang|first16=Xiao|last17=Pritchard|first17=Benjamin P.|last18=Verma|first18=Prakash|last19=Schaefer|first19=Henry F.|last20=Patkowski|first20=Konrad|last21=King|first21=Rollin A.|last22=Valeev|first22=Edward F.|last23=Evangelista|first23=Francesco A.|last24=Turney|first24=Justin M.|last25=Crawford|first25=T. Daniel|last26=Sherrill|first26=C. David|title=Psi4 1.1: An Open-Source Electronic Structure Program Emphasizing Automation, Advanced Libraries, and Interoperability|journal=Journal of Chemical Theory and Computation|volume=13|issue=7|pages=3185–3197|year=2017|issn=1549-9618|doi=10.1021/acs.jctc.7b00174|pmid=28489372|pmc=7495355 |url=https://authors.library.caltech.edu/77457/1/acs%252Ejctc%252E7b00174.pdf}}</ref>
<ref name="Kahn2017">{{cite news|last1=Kahn|first1=Jeremy|title=Google Debuts Software to Open Up Quantum Computers for Chemists|url=https://www.bloomberg.com/news/articles/2017-10-23/google-debuts-software-to-open-up-quantum-computers-for-chemists|access-date=8 April 2018|work=Bloomberg Technology|publisher=Bloomberg LP|date=October 23, 2017|ref=Kahn2017}}</ref>
<ref name="Smith2020">{{cite journal |last1=Smith|first1=Daniel G. A.|last2=Burns|first2=Lori A.|last3=Simmonett|first3=Andrew C.|last4=Parrish|first4=Robert M.|last5=Schieber |first5=Matthew C. |last6=Galvelis |first6=Raimondas |last7=Kraus |first7=Peter |last8=Kruse |first8=Holger |last9=Di Remigio |first9=Roberto |last10=Alenaizan |first10=Asem |last11=James |first11=Andrew M |last12=Lehtola |first12=Susi |last13=Misiewicz |first13=Jonathon P. |last14=Scheuer |first14=Maximilian |last15=Shaw |first15=Robert A. |last16=Schriber |first16=Jeffrey B. |last17=Xie |first17=Yi |last18=Glick |first18=Zachary L. |last19=Sirianni |first19=Dominic A. |last20=O'Brien |first20=Joseph Senan |last21=Waldrop |first21=Jonathan M. |last22=Kumar |first22=Ashutosh |last23=Hohenstein |first23=Edward G. |last24=Pritchard |first24=Benjamin P. |last25=Brooks |first25=Bernard R. |last26=Schaefer III|first26=Henry F. |last27=Sokolov |first27=Alexander Yu. |last28=Patkowski |first28=Konrad |last29=DePrince |first29=A. Eugene |last30=Bozkaya |first30=Uğur |last31=King |first31=Rollin A. |last32=Evangelista |first32=Francesco A. |last33=Turney |first33=Justin M. |last34=Crawford |first34=T. Daniel |last35=Sherrill |first35=C. David | title=Psi4 1.4: Open-Source Software for High-Throughput Quantum Chemistry|journal=Journal of Chemical Physics|volume=152|pages=184108|year=2020|issue=18 |doi=10.1063/5.0006002|pmid=32414239|pmc=7228781 |bibcode=2020JChPh.152r4108S |hdl=10138/321376 |hdl-access=free }}</ref>
}}

==External links==
* [http://www.psicode.org Psi4 Homepage]
* [https://github.com/psi4/psi4 Psi4 Source Code (GitHub)]

{{Chemistry software}}

{{DEFAULTSORT:Psi (Computational Chemistry)}}
[[Category:Computational chemistry software]]
[[Category:Free chemistry software]]
[[Category:Chemistry software for Linux]]