The Photo-Induced Structural Change in a Se Chain and a Se₈ Ring: an ab initio Molecular-Dynamics Simulation

Abstract

The structural change in a Se chain and a Se₈ ring due to the excitation of an electron in the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) is investigated by an ab initio molecular-dynamics simulation to clarify the possibility of bond breaking. It is shown, from the calculated time dependence of the bond lengths, the energy eigenvalues and the wavefunctions, that there occurs a photo-induced bond breaking in both cases and that such a bond breaking is closely related to the stabilization of the anti-bonding LUMO state. This photo-induced bond breaking may be considered as an elemental process for the recently observed photo-induced semiconductor-metal transition in liquid Se near the triple point. The results for Se₈ ring are also compared with our previous results for S₈ ring.