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A comparison of ground‐state averages in electron propagator theory
Author(s) -
Ortiz J. V.
Publication year - 1993
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.560480841
Subject(s) - propagator , coupled cluster , perturbation theory (quantum mechanics) , excitation , ground state , methods of contour integration , rotation formalisms in three dimensions , physics , electron , electronic correlation , self energy , cluster expansion , quantum mechanics , open shell , cluster (spacecraft) , density matrix , quantum electrodynamics , mathematics , mathematical analysis , molecule , quantum , geometry , computer science , programming language
In the Dyson equation, the self‐energy describes all relaxation and correlation corrections to Koopmans's theorem. Energy‐independent contributions to the self‐energy depend on the one‐electron reduced density matrix of the reference state. Three formalisms for calculating these terms are considered: perturbation theory, coupled‐cluster theory, and contour integral theory. In one method, combinations of coupled‐cluster singles and doubles amplitudes are substituted for first‐order double excitation coefficients and for second‐order single excitation coefficients. Another approach generates a description of reference state correlation through the evaluation of approximate contour integral expressions. Calculations on electron binding energies of closed‐shell molecules and anions reveal that the coupled‐cluster results for the energy‐independent self‐energy terms are closer to the perturbative results than to the contour integral values. © 1993 John Wiley & Sons, Inc.