PSI (computational chemistry)
Encyclopedia
PSI is an ab initio
computational chemistry
package originally written by the research group of Henry F. Schaefer, III
(University of Georgia
). It performs high-accuracy quantum computations on small to medium-sized molecule
s.
PSI3 is the latest release of the program package - it is open source
, released as free
under the GPL
through SourceForge
. Primary development is currently conducted by Daniel Crawford (Virginia Tech), David Sherrill (Georgia Tech), Edward Valeev (Virginia Tech), and Rollin King (Bethel University).
:
Several methods are available for computing excited electronic states, including configuration interaction singles (CIS), the random phase approximation (RPA), and equation-of-motion coupled cluster (EOM-CCSD). PSI3 also includes the explicitly-correlated MP2-R12 method and the ability to compute the Born-Oppenheimer diagonal correction using configuration interaction
wavefunction
s.
Ab initio quantum chemistry methods
Ab initio quantum chemistry methods are computational chemistry methods based on quantum chemistry. The term ab initiowas first used in quantum chemistry by Robert Parr and coworkers, including David Craig in a semiempirical study on the excited states of benzene.The background is described by Parr...
computational chemistry
Computational chemistry
Computational chemistry is a branch of chemistry that uses principles of computer science to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids...
package originally written by the research group of Henry F. Schaefer, III
Henry F. Schaefer, III
Henry "Fritz" Schaefer III is a computational and theoretical chemist. He is the author of a large number of scientific publications, and was the 6th most cited chemist from 1981 to 1997 and the Graham Perdue Professor of Chemistry and Director of the Center for Computational Chemistry at the...
(University of Georgia
University of Georgia
The University of Georgia is a public research university located in Athens, Georgia, United States. Founded in 1785, it is the oldest and largest of the state's institutions of higher learning and is one of multiple schools to claim the title of the oldest public university in the United States...
). It performs high-accuracy quantum computations on small to medium-sized molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s.
PSI3 is the latest release of the program package - it is open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
, released as free
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
under the GPL
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
through SourceForge
SourceForge
SourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...
. Primary development is currently conducted by Daniel Crawford (Virginia Tech), David Sherrill (Georgia Tech), Edward Valeev (Virginia Tech), and Rollin King (Bethel University).
Features
The basic capabilities of PSI are concentrated around the following methods of quantum chemistryQuantum chemistry
Quantum chemistry is a branch of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems...
:
- Hartree-FockHartree-FockIn computational physics and chemistry, the Hartree–Fock method is an approximate method for the determination of the ground-state wave function and ground-state energy of a quantum many-body system....
- Coupled clusterCoupled clusterCoupled cluster is a numerical technique used for describing many-body systems. Its most common use is as one of several quantum chemical post-Hartree–Fock ab initio quantum chemistry methods in the field of computational chemistry...
- CASSCF
- multireference configuration interactionMultireference configuration interactionIn quantum chemistry, the multireference configuration interaction method consists in a configuration interaction expansion of the eigenstates of the electronic molecular Hamiltonian in a set of Slater determinants which correspond to excitations of the ground state electronic configuration but...
methods.
Several methods are available for computing excited electronic states, including configuration interaction singles (CIS), the random phase approximation (RPA), and equation-of-motion coupled cluster (EOM-CCSD). PSI3 also includes the explicitly-correlated MP2-R12 method and the ability to compute the Born-Oppenheimer diagonal correction using configuration interaction
Configuration interaction
Configuration interaction is a post-Hartree–Fock linear variational method for solving the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathematically, configuration simply describes the linear combination...
wavefunction
Wavefunction
Not to be confused with the related concept of the Wave equationA wave function or wavefunction is a probability amplitude in quantum mechanics describing the quantum state of a particle and how it behaves. Typically, its values are complex numbers and, for a single particle, it is a function of...
s.
See also
- List of quantum chemistry and solid state physics software