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Brillouin-Wigner perturbation theory approximation

Whereas the multi-reference Rayleigh-Schrodinger perturbation theory approximates a manifold of states simultaneously, the multi-reference Brillouin-Wigner perturbation theory approach is applied to a single state - it is said to be state-specific . The multi-reference Brillouin-Wigner perturbation theory avoids the intruder state problem. If a particular Brillouin-Wigner-based formulation is not a valid many-body method, then a posteriori correction can be applied. This correction is designed to restore the extensivity of the method. This extensivity may be restored approximately... [Pg.31]

In Section 4.2.3.2, we presented the basic equations of single-root (state-specific) multi-reference Brillouin-Wigner coupled cluster theory. We derived these equations from the single-root (state-specific) multi-reference Brillouin-Wigner perturbation theory presented in Section 4.2.3.1. In this section, we turn our attention to the coupled cluster single- and double-excitations approximation, ccsd. We present... [Pg.159]


See other pages where Brillouin-Wigner perturbation theory approximation is mentioned: [Pg.20]    [Pg.471]    [Pg.52]    [Pg.53]    [Pg.32]    [Pg.134]    [Pg.134]    [Pg.135]    [Pg.156]    [Pg.156]    [Pg.178]    [Pg.193]    [Pg.93]    [Pg.467]    [Pg.592]    [Pg.1706]    [Pg.194]    [Pg.202]    [Pg.253]   
See also in sourсe #XX -- [ Pg.39 , Pg.229 ]




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