Quantum cluster equilibrium theory of liquids: light and heavy QCE/3-21G model water

The quantum cluster equilibrium (QCE/3-21G level) theory of water gives ris e to a qualitatively reasonable ice-like phase and to an authentic QCE trip le point that exhibits many similarities to the physical H2O phase diagram. The simple 18-cluster QCE/3-21G treatment comprises ring, tetrahedral and fullerene-like clusters up to 26-mers. We now extend the QCE theory to deut erated water clusters and characterize the microstructural composition and macroscopic properties in comparison to those obtained for the protonated s pecies. The QCE triple points for light and heavy water are examined for th eir dependence on energetics and vibrational properties of constituent clus ters.