Structural study of molten Ag halides and molten AgCl–AgI mixture

Abstract The structures of molten Ag halides and pseudo-binary mixtures between AgCl and AgI have been investigated by neutron diffraction measurements. For AgI, a crystalline local configuration persists even in the molten state while, for AgCl and AgBr, the first neighbor coordination number decreases to 3.4 compared with 6 in the crystalline rock salt structure and the second neighbor distribution is modified according to the shortening of Ag–halogen distance. This difference between AgI and AgCl (AgBr) may be originated from the nature of unlike-pair bonding. The former has much covalent character. The eutectic mixture between AgCl and AgI, AgCl0.43I0.57, exhibits large temperature dependence in the total structure from the AgCl like feature at a lower temperature to the AgI like feature at a high temperature. As increasing temperature, Cl ions become more diffusive and relatively strong interaction between Ag and I rules physical property such as sound absorption.