Abstract
A modified Hubbard-Beeby theory is used to calculate the dynamical structure factors of the superionic conductor α-AgI. It is found that the partial dynamical structure factors of cations and anions are almost the same at long wavelengths but very different at short wavelengths. From analysis of the partial dynamical structure factors it is found that the vibrational motion of cations is strongly correlated with the low-frequency longitudinal acoustic mode of the anion sublattice at long wavelengths. It is also found that this cation motion has no correlation with the high-frequency longitudinal optical mode of the anion sublattice at short wavelengths. These results closely resemble those of the molecular dynamics performed by Kaneko and Ueda except for the lack of a quasielastic peak. However, the cation motion has a strong correlation with the longitudinal acoustic mode even at short wavelengths.
