Comparison of models to correlate electron density at the bond critical point and bond distance

Two models proposed in the literature to correlate the electron density at the bond critical point with the bond distance have been compared. The firs t one, proposed independently by Knop-Boyd and Destro, considers an implici t double logarithmic relationship between these two properties. We propose a second model, which uses a logarithmic relationship. Van der Waals and hy drogen bond interactions as well as traditional covalent bonds have been co nsidered in order to have a broader range of the compared properties. The r esults indicate that both models provide good results when individual bond types are correlated, although the logarithmic model seems to be slightly b etter than the double logarithmic one. Finally, a unique equation correspon ding to model 2 has been devised to correlate all the H-X or C-X bonds. (C) 2000 Elsevier Science B.V. All rights reserved.