The BEBOP hybridization parameters are assigned to be the ROCBS-QB3 atomic 2s→ 2p excitation energies given in Table . The reference molecules in Table were used to determine the remaining parameters. In most cases, they represent the strongest bond that can be formed between the pair, A,B. However, in four cases (i.e., HBe -BeH vs. Be 4 , HBe-OH vs. Be --O, HBe -F vs. FBe -F, and cyclo-BC 2 H 3 vs. HB --CH 2 ), we found significant differences in parameter values for alternative reference choices and compromised with an average for the species in Table . The bond energy parameter, β AB (Table ), was constrained to reproduce the ROCBS-QB3 atomization energy, ∆ AT E 0 , of the reference species. These parameters are in general qualitatively similar (i.e., ranging from 1/2 to 2 times) to the extended Hückel theory values,