Structural properties, single-particle dynamics, and the charge transport are studied in superionic conductor Ag2Se using the molecular dynamics (MD) technique. The calculations are based on a model of interionic potentials in which ions interact through Coulomb interaction, steric repulsion and charge-dipole interaction due to the large electronic polarizability of the selenium ions. Structural and dynamics correlations are studied at five temperatures in the superionic phase. Among the structural correlations the results are presented for partial pair correlation function, coordination numbers, bond angle distributions and wave-vector dependence of the Bragg intensities. Detailed comparison with neutron and x-ray single crystal diffraction experiments. The calculated temperature dependence of the self-diffusion constant of silver is in good agreement with the tracer diffusion measurements. The spectra of velocity autocorrelation functions and the frequency dependent ionic conductivity are calculated. The Haven's ratio is also in good agreement with experiments.
Effective interatomic potentials consisting of two-body (steric effect, charge transfer and charge-dipole interactions) and three-body covalent forces are proposed for GeSe2. Using these interaction potentials in MD simulations, the nature of short-range and medium-range order is investigated in glassy and molten GeSe2. All the features in the static structure factor, S(q), including the first sharp diffraction peak (FSDP), are in good agreement with experiments. The FSDP arises from Ge-Ge and Ge-Se correlations between 4-8Å, and the anomalous decrease in its height on cooling is due to frustration enhanced by the increased density.