Original sentence: A series of ab initio studies of Si2H2 is an example of how ab initio computational chemistry can predict new structures that are subsequently confirmed by experiment.Al2H2 and Ga2H2 have exactly the same isomers, in spite of having two electrons less than the Group 14 molecules.In early studies, by Binkley and Lischka and Kohler, it became clear that linear Si2H2 was a transition structure between two equivalent trans-bent structures and that the ground state was predicted to be a four-membered ring bent in a 'butterfly' structure with hydrogen atoms bridged between the two silicon atoms.The methods used were mostly post-Hartree-Fock, particularly configuration interaction (CI) and coupled cluster (CC).Then a new isomer with an unusual structure was predicted by Brenda Colegrove in Henry F
Edited sentence: A series of ab initio studies of Si2H2 shows clearly the power of ab initio computational chemistry.More interestingly, similar results were obtained for Al2H2 (and then Ga2H2).Slowly (because this started before geometry optimization was widespread), it became clear that linear Si2H2 was a transition structure between two equivalent trans-bent structures and that it was rather high in energy.The ground state was predicted to be a four-membered ring bent into a 'butterfly' structure with hydrogen atoms bridged between the two silicon atoms.The methods used were mostly post-Hartree-Fock, particularly Configuration interaction (CI) and Coupled cluster (CC).Then surprisingly a new isomer was predicted by Brenda Colegrove in Henry F.This prediction was so surprising that it needed extensive calculations to confirm it.which has two electrons less than the Group 14 molecules