topological descriptor hybridization ratio It reports the fraction of sp3 carbons to sp2 carbons as Nsp3/ (Nsp3 + Nsp2). The original form of the descriptor (i.e., simple ratio) has been used to characterize molecular complexity, especially in the are of natural products , which usually have a high value of the sp3 to sp2 ratio. Other short names: HybridizationRatio, HybRatio. hybratio Characterizes molecular complexity in terms of carbon hybridization states.