  Results of systematic molecular dynamics studies of ethanol-water mixtures,
over the entire concentration range, were reported previously to agree with
experimental X-ray diffraction data. These simulated systems are analyzed in
this work to examine cluster formation and percolation, using four different
hydrogen bond definitions. Percolation analyses revealed that each mixture
(even the one containing 80 mol % ethanol) is above the 3D percolation
threshold, with fractal dimensions, df, between 2.6 to 2.9, depending on
concentration. Monotype water cluster formation was also studied in the
mixtures: 3D water percolation can be found in systems with less than 40 mol %
ethanol, with fractal dimensions between 2.53 and 2.84. These observations can
be put in parallel with experimental data on some thermodynamic quantities,
such as the excess partial molar enthalpy and entropy.
