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Comparison of perturbative and multiconfigurational electron propagator methods
Author(s) -
Zakrzewski V. G.,
Ortiz J. V.,
Nichols Jeffrey A.,
Heryadi Dodi,
Yeager Danny L.,
Golab Joseph T.
Publication year - 1996
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/(sici)1097-461x(1996)60:1<29::aid-qua3>3.0.co;2-7
Subject(s) - propagator , atomic orbital , wave function , diagonal , hamiltonian (control theory) , ionization energy , ionization , complete active space , quantum mechanics , physics , chemistry , valence (chemistry) , coupled cluster , fock space , linear combination of atomic orbitals , electron , atomic physics , mathematics , molecule , ion , mathematical optimization , geometry
Ionization energies below 20 eV of 10 molecules calculated with electron propagator techniques employing Hartree‐Fock orbitals and multiconfigurational self‐consistent field orbitals are compared. Diagonal and nondiagonal self‐energy approximations are used in the perturbative formalism. Three diagonal methods based on second‐ and third‐order self‐energy terms, all known as the outer valence Green's function, are discussed. A procedure for selecting the most reliable of these three versions for a given calculation is tested. Results with a polarized, triple ζ basis produce root mean square errors with respect to experiment of approximately 0.3 eV. Use of the selection procedure has a slight influence on the quality of the results. A related, nondiagonal method, known as ADC (3), performs infinite‐order summations on several types of self‐energy contributions, is complete through third‐order, and produces similar accuracy. These results are compared to ionization energies calculated with the multiconfigurational spin‐tensor electron propagator method. Complete active space wave functions or close approximations constitute the reference states. Simple field operators and transfer operators pertaining to the active space define the operator manifold. With the same basis sets, these methods produce ionization energies with accuracy that is comparable to that of the perturbative techniques. © 1996 John Wiley & Sons, Inc.