Bond length and the electron density at the bond critical point: XX, ZZ, and CZ bonds (X = Li-F, Z = Na-Cl)

✍ Scribed by Norberto Castillo; Katherine N. Robertson; S. C. Choi; Russell J. Boyd; Osvald Knop

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 211 KB
• Volume: 29
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.20795

✦ Synopsis

Abstract

The aim was to investigate the relationship between the bond length and the electron density at the bond critical point in homonuclear XX and ZZ and heteronuclear CZ bonds (X = Li‐F, Z = Na‐Cl). The d,ρ~c~ pairs were obtained from 472 target bonds in DFT‐optimized (B3LYP/6‐311+G(d,p)) small molecular species. These species were selected arbitrarily but with a view to maximize the range widths WR for each atom combination. It was found that (i) with one clear exception, the d(A − A) means (A = X or Z) correlate linearly with the bond lengths d(A~2~) of the respective diatomic molecules; (ii) the d(A − A) means correlate parabolically with n, the formal number of valence electrons in the atoms of the bond; and (iii) with increasing sample size N the ratio WR(ρ~c~)/WR(d) appears to converge toward a representation f [WR(ρ~c~)/WR(d)]~N→∞~ characteristic of A. Detailed analysis of the d,ρ~c~ relationship has shown that by and large simple power regression accounts best for the DFT data. The regression coefficients of d = a__ρ and ρ~c~ = α__d^−β^ (b, β > 0) vary with n in a seemingly irregular manner but one that is consistent with simple chemical notions. The d(A~2~) can be approximated in terms of multilinear MO electron occupancies. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008