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 rise to a qualitatively reasonable ice-like phase and to an authentic QCE triple 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 deuterated water clusters and characterize the microstructural composition and macroscopic properties in comparison to those obtained for the protonated species. The QCE triple points for light and heavy water are examined for their dependence on energetics and vibrational properties of constituent clusters.