Description of covalent bond orders using the charge density topology

Abstract

Hybrid density functional calculations are employed to explore the relationships between covalent bond order, as defined using the atomic overlap matrix (AOM) formalisms developed by Cioslowski, Ángyán and others, and the parameters derived from a topological analysis of the electron density. Relationships are obtained for the specific cases of C—C, C—N, C—O, C—P and C—S bonds. The simple Pauling bond order–bond length relationship describes the data reasonably well in most cases, but the correlations show considerable scatter. Although no single parameter acts as a unified descriptor of bond order for all types of bond, in each case it is possible to find a model which describes the bond order data significantly better than the Pauling model based on bond length. The relationships presented can therefore be utilized to estimate rapidly the covalent part of the bond order from a topological analysis of the charge distribution for very large systems where the AOM‐based methods can become impractical to apply, and for charge density distributions which have been obtained from experiment (e.g. elastic x‐ray scattering). Copyright © 2003 John Wiley & Sons, Ltd.

Experimental evidence of a 3-centre, 2-electron covalent bond character of the central O–H–O fragment on the Zundel cation in crystals of Zundel nitranilate tetrahydrate

“…§ Topological bond orders were calculated using the fitted formula 26 n topo = a + b λ 3 + c (λ 1 + λ 2 ) + d ρ cp , with parameters a, b, c and d taken from literature. 21,27 …”

Bond Orders and Atomic Properties of the Highly Deformed Halogenated Fullerenes C60F18 and C60Cl30 Derived from their Charge Densities

“…A relationship that also uses the l i is given by Equation (2), [8] in which the coefficients a to d, from molecular theoretical calculations, are reported for a number of bond types in the literature. [8,9] …”

Theoretical studies of electronic structure and structural properties of anhydrous alkali metal oxalates

“…Electronic structures of these compounds are typical for ionic compounds, with sharp peaks in density of states indicating very small energy bands dispersion and Table 2 Topological properties of bond critical points in Li 2 C 2 O 4 and Na 2 C 2 O 4 calculated from SCF FP-LAPW total electron density: bond length R, Hessian matrix eigenvalues k 1 -k 3 , electron density in bond critical point q BCP (r), Laplacian r 2 q(r), ellipticity e, electrostatic potential at BCP V[q(r)], local electron energy density H e [q(r)], and bond orders n CM(HL) (Ciosłowski & Mixon's [34] formula, optimized by Howard & Lamarche [35]) almost entirely mutually exclusive occupation of energy states by alkali metal cations and electrons originating from oxalate anion constituents (carbon and oxygen atoms). On the other hand, the same states are co-occupied by carbon and oxygen 2s and 2p electrons, which is consistent with a picture of bonding within oxalate anion emerging from topological analysis.…”