Symmetry properties and the two-phase coexistence curve of a two-dimensional bonded lattice fluid

Abstract

By examining the symmetry properties of a two-dimensional bonded lattice fluid we are able to obtain in a simple way the two-phase coexistence curve and the line of symmetry. The authors show that, in the density-temperature plane, the line of symmetry, the analytically continued two-phase diameter and the curve on which the chemical potential is equal to the analytic continuation of its values along the coexistence curve are all distinct. These curves intersect at the critical point in nonzero angles. They examine the behaviour of the thermodynamic response functions on the coexistence curve and show that on the high-density branch of the curve, the isothermal compressibility and the coefficient of isobaric thermal expansion exhibit anomalies similar to those shown by the water system. They show also that the discontinuous change in the constant pressure heat capacity as the system changes from the high-density to the low-density phase becomes negative below a certain temperature.