Photo-induced polymerization in liquid sulfur studied by an ab initio molecular-dynamics simulation Original Research Article

We performed ab initio molecular-dynamics simulations for the liquid sulfur at 400 K, below the polymerization temperature Tp=432 K, by exciting electrons from the occupied states to the unoccupied states. To investigate the relaxation process, the electronic states are calculated without the electron excitation. It is found that after an electron excitation a bond in one of the S8 rings is easily broken and consequently the S8 ring turns out to be the S8 chain. After the electron excitation is stopped, the S8 chain does not reconstruct the S8 ring but a ‘tadpole’ structure is formed: The atom at the end of the S8 chain is connected to the second atom from the other end. We have also shown that the photo-induced polymerization occurs in the liquid sulfur when the S8 chains or the S8 tadpoles are close to each other by their ends.