Multiplicity of many-body wavefunctions using unrestricted Hartree-Fock reference functions

1988 ◽  
Vol 53 (10) ◽  
pp. 2203-2213 ◽  
Author(s):  
George D. Purvis ◽  
Hideo Sekino ◽  
Rodney J. Bartlett
Keyword(s):  
Perturbation Theory ◽  
Coupled Cluster ◽  
Spin Projection ◽  
Many Body ◽  
Spin Multiplicity ◽  
Reference Function ◽  
Hartree Fock ◽  
Many Body Perturbation Theory ◽  
Reference Functions

Spin multiplicity formulae for the correlated Many Body Perturbation Theory (MBPT) and Coupled Cluster (CC) methods based upon an unrestricted Hartree Fock (UHF) reference function are presented and applied to evaluate the multiplicity in calculations of first row atoms. Spin projection in CC theory is discussed.

Static Dipole Polarizabilities of C, N, O and F: The Importance of Spin Projection

1990 ◽  
Vol 193 ◽  
Author(s):  
C. Sosa ◽  
K. F. Ferris
Keyword(s):  
Perturbation Theory ◽  
Finite Field ◽  
Ground State ◽  
Wave Functions ◽  
Spin Projection ◽  
Dipole Polarizability ◽  
Many Body ◽  
Hartree Fock ◽  
Many Body Perturbation Theory ◽  
Dipole Polarizabilities

ABSTRACTThe static dipole polarizability for the ground state of C(3Π ), N(4∑+), O(3Π ) and F(2∑+ ) have been calculated using ab initio molecular orbital techniques. The polarizabilities are obtained from unrestricted Hartree-Fock and Many-Body Perturbation Theory wave functions with and without spin projection, which are computed by finite-field differentiation. The effect of spin contamination is shown to be important on the calculation of static dipole polarizabilities for the ground state of C, N, O and F.

scholarly journals Hartree–Fock many-body perturbation theory for nuclear ground-states

2016 ◽  
Vol 756 ◽  
pp. 283-288 ◽  
Author(s):  
Alexander Tichai ◽  
Joachim Langhammer ◽  
Sven Binder ◽  
Robert Roth
Keyword(s):  
Perturbation Theory ◽  
Ground States ◽  
Many Body ◽  
Hartree Fock ◽  
Many Body Perturbation Theory

scholarly journals Psi4 1.4: Open-Source Software for High-Throughput Quantum Chemistry

2020 ◽  
Author(s):  
Daniel Smith ◽  
Lori Burns ◽  
Andrew Simmonett ◽  
Robert Parrish ◽  
Matthew Schieber ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Quantum Chemistry ◽  
Open Source ◽  
Density Functional ◽  
Many Body ◽  
Hartree Fock ◽  
Large Numbers ◽  
Many Body Perturbation Theory ◽  
Infrastructure Project ◽  
Job Specification

<div> <div> <div> <p>Psi4 is a free and open-source ab initio electronic structure program providing Hartree–Fock, density functional theory, many-body perturbation theory, configuration interaction, density cumulant theory, symmetry-adapted perturbation theory, and coupled-cluster theory. Most of the methods are quite efficient thanks to density fitting and multi-core parallelism. The program is a hybrid of C++ and Python, and calculations may be run with very simple text files or using the Python API, facilitating post-processing and complex workflows; method developers also have access to most of Psi4’s core functionality via Python. Job specification may be passed using The Molecular Sciences Software Institute (MolSSI) QCSchema data format, facilitating interoperability. A rewrite of our top-level computation driver, and concomitant adoption of the MolSSI QCArchive Infrastructure project, make the latest version of Psi4 well suited to distributed computation of large numbers of independent tasks. The project has fostered the development of independent software components that may be reused in other quantum chemistry programs. </p> </div> </div> </div>

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