Analysis of diffusion constant and non-Gaussianity near the glass transition point in the frequency domain

A novel method is developed for estimating the diffusion constant D _c and the non-Gaussian parameter A(t) on the basis of measurement in the frequency region. This method is shown to have merits over the conventional one in which a limited time window is used. To confirm the validity of this method, it is applied to a binary soft-sphere fluid which was studied by molecular dynamics (MD) simulation. The diffusion constant D_c is determined in the region closer to the glass transition than in the conventional MD simulation. The temperature dependence of the exponent of A(t) is consistent with that predicted by the trapping diffusion model.