Neutron diffraction data and molecular dynamics simulations of the molten mixture Ag(Br0.7I0.3)

Abstract

The structure factors of the ionic liquid mixture Ag(Br(0.7)I(0.3)) at three temperatures, 723, 923, and 1023 K, as well as of the pure molten AgI at 923 K and the pure molten AgBr at 773 and 923 K, were studied experimentally and by means of molecular dynamics simulations. The experiments were carried out using the high intensity total scattering time-of-flight spectrometer, HIT-II, at the KENS spallation neutron source in Japan. The experimental data are very reliable, with the possible exception of the small momentum transfer region, whose accessibility is limited by neutron energy and detector positions. The simulations made use of the semiempirical rigid ion potentials of the Vashishta-Rahman [Phys. Rev. Lett. 40, 1337 (1978)] type using a new set of parameters appropriate for the mixture. Within the known constraints of the pairwise rigid ion potentials, the simulated structure factors are in fair agreement with experiment. The results for the pair distribution functions suggest that the molten mixture retains the superionic character found in previous calculations of both the AgI and AgBr melts. This suggestion is confirmed by the results for the self-diffusion coefficients. Values obtained for the ionic conductivities are also presented.

Molecular Dynamics Study of Polarization Effects on AgI

“…By using the potential models described above, we have simulated solid AgI at 573 K, the temperature at which Cava et al 4 carried out neutron diffraction measurements, and molten AgI at 923 K, the same at which recent neutron diffraction data are available. 36 The are short-range contributions and, thus, can be evaluated without the Ewald method. We have also carried out MD simulations of the RIM and PIM1 with 1000 ions, and we have verified that all the results are practically the same as those obtained with 500 ions.…”

Phase-boundary potential in the two-liquid-phase (AgI+NaCl) system

“…To a certain degree, the temperature variations of the interfacial tension, c, and of its components, c d and cD E , are subject to the same principle of corresponding states. The lower value of the experimentally derived critical exponent for the (AgI + NaCl) system than that found for the other alkali halide melts may be a manifestation of the presence of a covalent component in the bonding energy of the silver cation with the halide anion [25][26][27][28][29]. This was previously established for the temperature variation measured by the sound velocity method for (AgI + NaCl) systems near the critical temperature [22].…”

On the structure of the molten mixture Ag(I0.3Br0.7)

“…Here we report the results for the molten Ag(I 0.3 Br 0.7 ) mixture, at 650°C. The full set of results have since been published elsewhere [13].…”