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On the thermodynamics of nonuniform systems
Author(s) -
Metiu H.,
Ruckenstein E.
Publication year - 1971
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690170144
Subject(s) - disjoining pressure , thermodynamics , surface tension , nucleation , chemistry , mechanics , physics , wetting
Two methods are presented for the treatment of the nonuniform systems. Both have as a starting point the approximation of the real system by a succession of uniform systems (cells). In one of them, the nonuniformity is taken into account by attributing a free energy to the separating surfaces between the cells, while in the other by considering that the cells are under the action of an “external field” created by the nonuniformity. A distinction between small and large nonuniform systems is made by comparing the thickness of the nonuniform system with the length of the interval in which the nonuniformity is decaying. For small systems the intensive properties depend on the thickness of the system and thus some supplementary effects, as for instance the disjoining pressure, occur. An expression for the “external field” based on the formalism of the radial distribution function is proposed. A large number of phenomena, such as surface tension, adsorption, disjoining pressure, nucleation, the vapor pressure of a liquid imbibing a porous medium, the influence of a solid surface upon a chemical reaction, are treated in a unitary manner by means of the present approaches. Some previous equations such as those of Cahn‐Hilliard and of Hill are derived in a different manner or justified. The objections raised by Widom against the continuous approaches are discussed.