  Using density-functional molecular dynamics simulations we analyzed the
cooling-rate effects on the physical properties of GeS$_2$ chalcogenide
glasses. Liquid samples were cooled linearly in time according to $T(t) = T_0 -
\gamma t$ where $\gamma$ is the cooling rate. We found that our model leads to
a promising description of the glass transition temperature $T_g$ as a function
of $\gamma$ and gives a correct $T_g$ for experimental cooling rates. We also
investigated the dependence of the structural properties on the cooling rate.
We show that, globally, the properties determined from our simulations are in
good agreement with experimental values and this even for the highest cooling
rates. In particular, our results confirm that, in the range of cooling rates
studied here, homopolar bonds and extended charged regions are always present
in the glassy phase. Nevertheless in order to reproduce the experimental
intermediate range order of the glass, a maximum cooling rate should not be
exceeded in numerical simulations.
