First-principles study of the thermally induced polymerization of cyclopentasilane

The molecular structures and vibration modes of cyclopentasilane (Si5H10) have been examined by employing ab initio and density-functional methods. Three different structures of Si5H10 with different symmetries are analyzed, and the results show that the envelope (Cs) and the twist (C2) forms have similar energies and that the planar form (D5h) is about 50 meV less stable than the Cs and C2 forms. The ring-open reaction of Si5H10 is investigated in detail by using the first-principles molecular-dynamics simulation for screening the reaction pathways. The formation of Si-H-Si is found to play an important role in the ring-open reaction.