Relationships in the approach to criticality in fluids, including systematic differences between vapor--liquid and liquid--liquid systems
The available data on a number of vapor--liquid and liquid--liquid systems have been reexamined. The effective critical exponent is used to describe the approach to criticality for the two types of systems. The liquid--liquid critical systems have a small or zero first Wegner correction term, and are similar in this respect to the spin 1/2 Ising lattice. The gas--liquid critical systems have a much larger first Wegner term and are qualitatively similar to a high spin Ising lattice. By analyzing data for a number of fluids, we find strong support for a universal value for the first Wegner coefficient for vapor--liquid coexistence in simple fluids. The higher correction terms are substance dependent. These statements do not apply to ionic fluids which have quite different properties. The extent to which metals differ or are similar is examined briefly. The substance dependence of the leading critical amplitudes has also been examined with reference to the extensions of the corresponding states theorem. An approximate linear dependence of the amplitude on the acentric factor of the fluid is found.
- Research Organization:
- Department of Chemistry and Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
- OSTI ID:
- 6335199
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 90:10
- Country of Publication:
- United States
- Language:
- English
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