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Natural resonance theory: II. Natural bond order and valency
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<610::aid-jcc4>3.0.co;2-u
Subject(s) - valency , natural bond orbital , bond order , resonance (particle physics) , chemistry , sextuple bond , covalent bond , single bond , computational chemistry , valence bond theory , ionic bonding , bond length , density functional theory , atomic physics , molecule , molecular orbital , physics , organic chemistry , philosophy , linguistics , ion , alkyl
Abstract Resonance weights derived from the Natural Resonance Theory (NRT), introduced in the preceding paper are used to calculate “natural bond order,” “natural atomic valency,” and other atomic and bond indices reflecting the resonance composition of the wave function. These indices are found to give significantly better agreement with observed properties (empirical valency, bond lengths) than do corresponding MO‐based indices. A characteristic feature of the NRT treatment is the description of bond polarity by a “bond ionicity” index (resonance‐averaged NBO polarization ratio), which replaces the “covalent‐ionic resonance” of Pauling‐Wheland theory and explicity exhibits the complementary relationship of covalency and electrovalency that underlies empirical assignments of atomic valency. We present ab initio NRT applications to prototype saturated and unsaturated molecules methylamine, butadiene), polar compounds (fluoromethanes), and open‐shell species: (hydroxymethyl radical) to demonstrate the numerical stability, convergence, and chemical reasonableness of the NRT bond indices in comparison to other measures of valency and bond order in current usage. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 610–627, 1998