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Natural resonance theory: I. General formalism
Author(s) -
Glendening E. D.,
Weinhold F.
Publication year - 1998
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(19980430)19:6<593::aid-jcc3>3.0.co;2-m
Subject(s) - diagonal , resonance (particle physics) , density functional theory , density matrix , formalism (music) , delocalized electron , quantum mechanics , statistical physics , physics , mathematics , quantum , geometry , art , musical , visual arts
We present a new quantum‐mechanical resonance theory based on the first‐order reduced density matrix and its representation in terms of natural bond orbitals (NBOs). This “natural” resonance theory (NRT) departs in important respects from the classical Pauling‐Wheland formulation, yet it leads to quantitative resonance weights that are in qualitative accord with conventional resonance theory and chemical intuition. The NRT variational functional leads to an optimal resonance‐weighted approximation to the full density matrix, combining the “single reference” limit of weak delocalization (incorporating diagonal population changes only) with the full “multireference” limit of strong delocalization (incorporating off‐diagonal couplings between resonance structures. The NRT variational functional yields an error measure that serves as an intrinsic criterion of accuracy of the resonance‐theoretic description. The NRT program structure, algorithms, and numerical characteristics are described in supplementary material, and detailed chemical applications are presented in two companion papers. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 593–609, 1998