MECHANISM OF AG+ ORDERING IN AGI

We performed lattice Monte Carlo simulations to explore the suggestion made in our previous study of phase transitions in AgI using a lattic e version of the density-functional theory [Phys. Rev. B 56, 11485 (19 97)] that the phase transition from the high-temperature alpha phase t o the low-temperature beta phase is not driven by the ordering of Agions alone, but that instead ordering of Ag+ is correlated with a stru ctural change of the I- lattice. The results of our calculation are co nsistent with this proposal.