The high-temperature superionic behaviour of Ag2S

Powder neutron diffraction and molecular dynamics (MD) simulations have been used to investigate the structural behaviour of silver sulfide, Ag(2)S, at elevated temperatures. Above similar to450 K Ag(2)S adopts the phase in which the S(2-) possess a body-centred cubic arrangement. Analysis of the neutron diffraction is in good agreement with the previously proposed structural model in which the Ag(+) predominantly reside within the tetrahedral interstices. At similar to865 K Ag(2)S transforms to the a phase in which the anion sublattice adopts a face-centred cubic arrangement. Structural refinements of this phase indicate that the cations are distributed predominantly in the tetrahedral cavities but with a significant fraction in the octahedral holes. MD simulations, using established potentials for this compound, confirm the stability of the two high-temperature superionic phases and show good agreement with the measured Ag(+) distribution within the unit cell.