A Simple Definition of Ionic Bond Order

• Published in: Journal of chemical theory and computation Vol. 4; no. 10; pp. 1637 - 1642
• Main Author: Chesnut, D. B
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.10.2008
• Subjects: Quantum Electronic Structure
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/ct800326n

Taking the square of the bond ionicity, i μ 2(i,j), for molecular orbital μ in the localized orbital representation of Cisolowski and Mixon (J. Am. Chem. Soc. 1991 , 113, 4142−4145) as an ionic bond order, one finds a simple and natural relation between the covalent bond order, p cov, μ(i,j), and the ionic bond order, p i o n,μ(i,j): p i o n,μ(i,j) ≡ i μ 2(i,j) = 1 − [p cov, μ(i,j)]/[p cov, μ max (i,j)] where p cov, μ max (i,j) = t μ(i,j)2 is the maximum value p cov, μ(i,j) can attain and where t μ(i,j) is the total orbital occupancy of the atoms-in-molecules basins involved. A number of examples and limitations of the method are presented using the B3LYP/6−311+G(d,p) density functional approach.