  The hydrogen-bonded structure of methanol-water mixtures is investigated over
the entire alcohol concentration range (from $x_{\mathrm{Methanol}}=$ 0.1 to
1.0) at several temperatures, from 300 K down to the freezing point of the
given mixture. Classical molecular dynamics simulations have been carried out,
using the all-atom OPLS-AA force field for methanol and the TIP4P/2005 model
for water molecules. Simulation trajectories ('particle configurations')
obtained have been analyzed, in order to characterize the hydrogen-bonded
network in the mixtures. The temperature and concentration dependence of the
average hydrogen bond (H-bond) numbers between different types of molecules,
the donor/acceptor roles of water and methanol molecules, and hydrogen bond
number distributions have been revealed. The topology of the total system, as
well as that of the water and methanol subsystems, has been investigated by
calculating the cluster size distributions, the number of primitive rings, and
ring size and ring type distributions. It has been found that upon cooling, the
average number of H-bonded water molecules increases at every concentration and
temperature investigated. As far as the connectivity of the hydrogen-bonded
network is concerned, the percolation threshold has been shown to be above
$x_{\mathrm{M}}=$ 0.9 already at room temperature.
