Abstract :
While bonding parameters such as electron localization function (ELF) bond basin populations and atoms-in-molecules (AIM) delocalization indices may not in an absolute sense reflect our simple ideas of bond orders, ratios of these parameters referenced to a suitable standard may be a more viable measure of the bonding situation. In the present paper we have calculated both these quantities for the bonds between heavy atoms for all the simple two-heavy-atom hydrides and diatomics capable of multiple bond formation for elements in the first two long rows of the periodic table and have compared the ratios of these parameters relative to the arbitrarily chosen double bond case. We find that a division into clearly defined formal bond-order classes occurs for the AIM delocalization index and is apparent thought less clear for ELF bond basin populations. The division agrees with our intuitive chemical ideas regarding formal bond order and should be a useful tool in characterizing general bonding situations.
