Order-disorder phase transition and dissociation of hydrogen sulfide under high pressure: Ab initio molecular dynamics study

The structural and dynamical properties of phase IV and V of hydrogen sulfide were investigated by means of extensive ab initio molecular dynamics simulations. Starting from an experimental proposal for the structure of phase IV, an Ibca symmetry with a stable hydrogen bonding network is found at 15 GPa and 100 K. Molecular dynamics simulations at increasing temperature and at the pressure of 15 GPa suggest that phase IV will transform to a proton disordered structure at 15 GPa and 350 K. The newfound structure has a hexagonal lattice of P63/mmc symmetry, which is believed to be the remaining crystalline structure of phase V. The high mobility of protons in phase V is believed to be the key point to the dissociation and decomposition of hydrogen sulfide.