Premium
Generator coordinate approximation to nuclear electronic coupling
Author(s) -
Broeckhove J.,
Lathouwers L.,
Vanderheyden G.
Publication year - 1988
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.560340852
Subject(s) - adiabatic process , adiabatic theorem , maxima and minima , feynman diagram , vibronic coupling , formalism (music) , physics , wave function , potential energy , generator (circuit theory) , born–oppenheimer approximation , quantum mechanics , mathematics , mathematical analysis , molecule , power (physics) , art , musical , visual arts
The Generator Coordinate Approximation ( GCA ) is the general approximation scheme for molecular systems devised to improve the Adiabatic Approximation ( AA ). This is achieved by replacing the familiar product‐type molecular wave function by a convolution product‐like state. One can demonstrate via Born‐Oppenheimer perturbation theory that for vibration‐rotation levels near potential energy minima the GCA results are bracketted by the exact and adiabatic values, subject to the use of good quality electronic states as input (e.g., the Hellman‐Feynman theorem needs to be satisfied accurately). We investigate the relevance of the GCA for energy levels near avoided crossing regions using a system modeled on the EF 1 Σ + gstate of hydrogen. The results of numerical experiments on this system are very encouraging (80–90%) of the nonadiabatic effects is recovered. This numerical success awaits theoretical explanation.