title: Bond length and the electron density at the bond critical point: X--X, Z--Z, and C--Z bonds (X = Li-F, Z = Na-Cl).
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,rho(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(rho(c))/WR(d) appears to converge toward a representation f [WR(rho(c))/WR(d)](N-->infinity) characteristic of A. Detailed analysis of the d,rho(c) relationship has shown that by and large simple power regression accounts best for the DFT data. The regression coefficients of d = arho(c) (-b) and rho(c) = alphad(-beta) (b, beta > 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.
authors.affiliation: Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Norberto
authors.initials: N
authors.lastname: Castillo
authors.forename: Katherine N
authors.initials: KN
authors.lastname: Robertson
authors.forename: S C
authors.initials: SC
authors.lastname: Choi
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Boyd
authors.forename: Osvald
authors.initials: O
authors.lastname: Knop
mesh_terms: D002244:Carbon / Q000737:chemistry*; D003198:Computer Simulation; D004583:Electrons; D005459:Fluorides / Q000737:chemistry*; D018020:Lithium Compounds / Q000737:chemistry*; D008956:Models, Chemical; D012965:Sodium Chloride / Q000737:chemistry*
chemical_list: D018020:Lithium Compounds; C027651:lithium fluoride; D012965:Sodium Chloride; D002244:Carbon; D005459:Fluorides