Badgerʹs rule revisited

Numerical experiments demonstrate that the accuracy of stretching force constants ke provided by Badgerʹs rule is unlikely to be substantially improved either by modification of the functional dependence on the equilibrium bond length Re or the inclusion of bond parameters related to electron density. These results, based upon both the experimental and QCISD/6-311++G(3d2f, 3p2d) values of Re and ke, imply that most of the universal characteristics of the bond strength vs. bond length dependence are accounted for by Badgerʹs rule, the more detailed features being unexplainable by first-order response properties such as electron density.