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The QDPT CI approach for excitation and ionization spectra: A test on the CO molecule
Author(s) -
Lisini A.,
Decleva P.
Publication year - 1995
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.560550310
Subject(s) - excitation , ionization , atomic physics , eigenfunction , perturbation theory (quantum mechanics) , valence (chemistry) , degenerate energy levels , ionization energy , spectral line , configuration interaction , basis set , eigenvalues and eigenvectors , molecule , chemistry , physics , excited state , quantum mechanics , ion
A detailed analysis of the performance of the QDPT CI method, which is based on the application of quasi‐degenerate perturbation theory ( QDPT ) within the configuration interaction ( CI ) approach, is presented by comparing the QDPT CI results and those obtained from the diagonalization of the perturbative space. Calculations of core and valence excitation and ionization spectra of the CO molecule, which is a strongly correlated system, are carried out using a DZ basis set and the accuracy of the eigenvalues and eigenfunctions is checked through the comparison of excitation and ionization energies and intensities. Excellent agreement is obtained for all values, indicating the computational advantages of QDPT CI which is able to explore wide energy ranges without requiring the diagonalization of large spaces. © 1995 John Wiley & Sons, Inc.