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A second‐quantization approach to the analytical evaluation of response properties for perturbation‐dependent basis sets
Author(s) -
Helgaker Trygve U.,
Almlöf Jan
Publication year - 1984
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.560260211
Subject(s) - perturbation (astronomy) , fock space , hamiltonian (control theory) , basis set , basis (linear algebra) , quantization (signal processing) , second quantization , perturbation theory (quantum mechanics) , statistical physics , computational chemistry , physics , mathematics , quantum mechanics , chemistry , algorithm , quantum , molecule , mathematical optimization , geometry , creation and annihilation operators
A general theory for response properties is presented which is applicable to perturbations affecting the molecular basis set, notably nuclear derivatives. A perturbation‐independent Fock space is introduced, and the necessary reorthonormalization of a truncated basis set after a perturbation is explicitly incorporated in the Hamiltonian. Explicit formulas for MCSCF first‐ and second‐order properties are presented, and some computational aspects are briefly discussed. A brief comparison with previous results is given.