Premium
Different forms of perturbation theory for the calculation of the correlation energy
Author(s) -
Murray Christopher,
Davidson Ernest R.
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560430604
Subject(s) - open shell , møller–plesset perturbation theory , atomic orbital , hamiltonian (control theory) , perturbation theory (quantum mechanics) , perturbation (astronomy) , electronic correlation , physics , quantum mechanics , poincaré–lindstedt method , mathematical physics , statistical physics , mathematics , molecule , mathematical optimization , electron
Different forms of perturbation theory for the calculation of correlation energy in both closed‐and open‐shell systems are discussed. For closed‐shell systems, Epstein–Nesbet perturbation theory is compared with Møller–Plesset ( MP ) perturbation theory based on canonical Hartree–Fock orbitals and with MP theory based on internally consistent SCF orbitals. The traditional MP theory gives superior results despite its use of an inferior zeroth‐order Hamiltonian. This behavior is rationalized in terms of the larger denominators present in the traditional MP theory. These conclusions are used to support the restricted open‐shell perturbation methods proposed recently by Murray and Davidson, and these new methods are compared with spin‐restricted Epstein–Nesbet theory and the unrestricted MP ( UMP ) approach. © 1992 John Wiley & Sons, Inc.