title: Quantum Cluster Equilibrium Theory Applied in Hydrogen Bond Number Studies of Water. 2. Icebergs in a Two-Dimensional Water Continuum?
abstract: With the aid of the quantum cluster equilibrium method, we calculate thermodynamic properties for a new water cluster set containing 2-fold and additional tetrahedrally hydrogen-bonded water molecules on the basis of accurate correlated electronic structure calculations. The addition of clusters with 4-fold coordinated water molecules leads to an improved thermodynamical description of the liquid phase in comparison to experimental values. The comparison of the obtained isobars from the pure 2-fold cluster set with the mixed cluster set shows improved results for the mixed set. Furthermore, the results of the liquid-phase entropy calculation compare excellently with experiment if the mixed cluster set is applied. The calculated populations allow us to determine hydrogen bond numbers, resulting in a temperature-dependent average hydrogen bond number. We observe a decreasing average hydrogen bond number of 2.77 at 274 K to 2.26 at 373 K and a dominance of 75% 2-fold hydrogen-bonded water molecules at room temperature for the mixed cluster set.
authors.affiliation: Wilhelm-Ostwald Institute of Physical and Theoretical Chemistry, University of Leipzig, Linnéstrasse 2, D-04103 Leipzig, Germany.
authors.forename: S B C
authors.initials: SB
authors.lastname: Lehmann
authors.affiliation: Wilhelm-Ostwald Institute of Physical and Theoretical Chemistry, University of Leipzig, Linnéstrasse 2, D-04103 Leipzig, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Spickermann
authors.affiliation: Wilhelm-Ostwald Institute of Physical and Theoretical Chemistry, University of Leipzig, Linnéstrasse 2, D-04103 Leipzig, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Kirchner