Molecular dynamics simulation of premelting effect in AgBr

Thermodynamic Properties of AgCl and AgBr

“…The heat capacity must therefore contain a component due to the change in disorder with temperature. Silver chloride and silver bromide are well-known examples of compounds with predominant Frenkel disorder of the cations in the crystal lattice. – A significant disorder in these compounds ,,– appears at temperatures about (100 to 200) K lower than the melting temperatures, which is in excellent agreement with our heat capacity experimental results.…”

“…On the other hand, the data of Pankratz are incorrect too. These data suggest the possibility of disordering starting at ambient temperature, which has not been reported in the literature ,,– nor found in the course of our experimental determinations. Also, heat capacity evolution when approaching the AgCl and AgBr melting temperature seems inconsistent with a widely accepted premelting disorder.…”

“…Ionic transport properties of silver halides have attracted special attention for a long time. – There were two main questions concerning the understanding of experimental results on these materials. The first, what is the mechanism of ion transport in each of these compounds, and the second, how does ionic conduction relate to other physical properties.…”

Structure and Ionic Transport Properties of AgI1–xBrx within Single-Wall Carbon Nanotubes from Molecular Dynamics Simulation

“…The calculated values of E a for the ion-conducting solid nanophase are definitely higher than those typical for genuine superionics (<0.2 eV; the experimental values for α-AgI are 0.1−0.12 eV, both in the bulk and in grains ≤200 Å in size 54,93 ) but significantly lower than the experimental diffusion activation energy of AgBr at "premelting" temperatures 57,94 (>1 eV) or the rocksalt-like AgI polymorph at temperatures where it shows high ionic conduction 54 (about 0.9 eV). They are also much lower than the experimental activation energies of silver diffusion in nanosized AgI grains in the temperature range of the β/γ → α transition 93 (about 1.6 eV; the transition is diffuse in nano-AgI, not a sharp one as in the bulk phase).…”