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A classification of open‐shell states of molecules
Author(s) -
Wasilewski Jan
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)57:4<625::aid-qua10>3.0.co;2-#
Subject(s) - open shell , shell (structure) , physics , chemistry , computational chemistry , atomic physics , materials science , composite material
A proposal for the classification of molecular open‐shell states is presented. This classification can be applied to most standard situations, well described within the Born‐Oppenheimer and nonrelativistic approximations. The main idea is to consider electronic configurations important in the CI ‐type expansion of the state wave function at the equilibrium conformation, as well as along any generalized coordinate describing a physically realistic conformational transformation, in particular, the system separation in the state considered. The states are generally divided into single‐ and multireference ones. On the basis of the conformational dependence of the multireference character, the states are further divided into locally, asympotically, globally, and strongly multiconfigurational ones. The proposed classification is an attempt at a unifying view of such well‐known phenomena, like avoided crossings, Woodward‐Hoffman forbidden processes, conical intersections, Jahn‐Teller stabilizations, and van der Waals minima. A comparison with the classification of Kutzelnigg and Smith [ Int. J. Quantum Chem. 2 , 531 (1968)], based on an analysis of natural orbital occupation numbers, is made wherever possible. © 1996 John Wiley & Sons, Inc.