Design of New Material with High Ionic Conductivity

A computer simulation by a molecular dynamics method at constant volume has been performed to a model system which is composed of accumulating two different ionic conductors: ···AgI-Ag 2 S-AgI-Ag 2 S···. Along the c -axis ( z -axis), AgI-parts are compressed and Ag 2 S-parts are stretched. About 3% of Ag ions in Ag 2 S-parts have been transfered to AgI-parts. The self-diffusion coefficient of Ag ions in AgI-parts decreases by 40-50% compared with that in a single AgI-system, while the diffusion coefficient of Ag ions in Ag 2 S-parts increases by 30% compared with that in a single Ag 2 S-system. The ionic conductivity of the superlattice-system is larger than that of either material of the AgI-system or Ag 2 S-system. The calculation suggests the possibility of the existence of a new material which has a larger ionic conductivity.