Phase Diagrams of a Simple H-Bonded Lattice Gas Obtained With The Cluster Variation Method

摘要

We evaluate the Bell-lattice-model for water by exploring the parameter space by means of the Cluster Variation method of Kihuchi. We use ten order parameters to describe the different occupation of tetrahedrons in the lattice, with and without hydrogen bonds. The phase diagrams are represented in the density-temperature plane and in the pressure temperature plane. An explanation is given as to why there are first order terminal points in the metastable region. We discuss the 180 degree rule and display the ratios of hydrogen bonded pairs versus non-hydrogen bonded pairs. (Author)