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Rayleigh–Schrödinger perturbation theory for many‐electron systems with partitioning of configurations by orders of excitation. II. Analysis of the ground state wavefunction and energy
Author(s) -
Taylor William J.
Publication year - 1986
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.560290523
Subject(s) - wave function , perturbation theory (quantum mechanics) , excited state , physics , ground state , perturbation (astronomy) , quantum mechanics , coupled cluster , quantum electrodynamics , electron , molecule
Rayleigh‐Schrödinger perturbation theory has been rederived by an extension of Löwdin's partitioning method in which excited configurations are partitioned by their orders. The resulting equations show explicityly how first‐, second‐, and third‐order configurations contribute to the first three orders of perturbative corrections to the ground‐state wavefunction, and the first seven orders of corrections to the groundstate energy. The corrections to the energy have also been expressed in terms of the coefficients in the wavefunction by an independent derivation; this yields more compact expressions for the energy corrections. The results are summarized in three convenient tables. The relation of the results for the energy to the requirement of size consistency, and the linked cluster theorem of many‐body perturbation theory, is discussed.