Ion conduction mechanisms of silver halides under high pressures.

AgI can transform a face-centred cubic lattice structure under pressures in the range 0.4–11.3 GPa. These phases also exhibit high ionic conductivities, particularly at high temperatures. The full-potential linear muffin-tin-orbital (FP-LMTO) method is used to investigate the ion conduction mechanisms of AgI under high pressures, wherein the exchange correlation energies of electrons are calculated via both local density approximation and generalised gradient approximation and then compared. The total energy calculations exhibit saddle points along the migration pathways, where Frenkel defects should be stable. Our results suggest that Frenkel defects do not easily migrate from stable positions, particularly under high pressures. This implies that Frenkel defects dominate ionic conduction not only in AgCl and AgBr, but also in rocksalt-structured AgI. [ABSTRACT FROM AUTHOR]