Configurational properties and corresponding states in simple fluids and water

Using accurate equations of state, contributions to the configurational ent ropy and energy of water are calculated and compared with six simple fluids and a model Lennard-Jones (LJ) fluid. The reorganizational entropy is calc ulated for the first time for water and other fluids. Comparisons are made at equal reduced densities from the triple point to the gas-liquid critical temperature. A corresponding states principle (CSP), suggested by the van der Waals model, is satisfied for certain configurational properties among the simple and LJ fluids. Saturated simple liquids in states of-equal free volume fractions have comparable configurational properties. Water deviates significantly from the CSP in some but not all cases, The normal boiling p oint of eight simple fluids is seen to be an isofree volume state that occu rs at a reduced density (rho/rho(c)) of 2.63 +/- 0.02, or equivalently, an occupied volume fraction of 0.42. A nearly invariant entropy of vaporizatio n at the normal boiling point among eight simple fluids ((9.1 +/- 0.3)k) is one manifestation of the CSP (Trouton's rule). The LJ model fluid accurate ly describes the configurational properties of argon and methane. This resu lt lends credibility to the wide spread use of the LJ potential to describe atom-atom (or site-site) interactions in large and complex molecules.