Quantum cluster equilibrium theory of liquids: molecular clusters and thermodynamics of liquid ethanol

Quantum cluster equilibrium (QCE) theory is presented for liquid ethanol. T he cluster equilibria that dictate phase composition are determined by the rigorous techniques of quantum statistical thermodynamics in the canonical ensemble, based on the ab initio partition function. The characteristic fea tures of the supramolecular clusters which comprise the QCE model are discu ssed in terms of binding energies, geometries, cooperativity and charge tra nsfer. The validity of the resulting QCE model is demonstrated by compariso n with experimental thermodynamic data: Clausius-Clapeyron pressure;tempera ture dependence and the specific heat. At room temperature, neat, liquid et hanol consists of approximately equal parts of monomer, cyclic tetramer and cyclic pentamer clusters.