Structural evolution and molecular dissociation of H_(2)S under high pressures

Solid H_(2)S as the precursor for H_(3)S with incredible superconducting properties under high pressure,has recently attracted extensive attention.Here in this work,we propose two new phases of H_(2)S with P42/n and I41/a lattice symmetries in a pressure range of 0 GPa–30 GPa through first-principles structural searches,which complement the phase transition sequence.Further an ab initio molecular dynamics simulation confirms that the molecular phase P2/c of H_(2)S is gradually dissociated with the pressure increasing and reconstructs into a new P2_(1)/m structure at 160 GPa,exhibiting the superconductivity with Tc of 82.5 K.Our results may provide a guidance for the theoretical study of low-temperature superconducting phase of H_(2)S.