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Chemical, quasi‐chemical and perturbation theories for associating fluids
Author(s) -
Economou Ioannis G.,
Donohue Marc D.
Publication year - 1991
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.690371212
Subject(s) - statistical physics , perturbation theory (quantum mechanics) , hydrogen bond , perturbation (astronomy) , chemistry , chemical bond , lattice (music) , thermodynamics , london dispersion force , molecule , physics , quantum mechanics , van der waals force , acoustics , organic chemistry
Pure fluids and mixtures of species that hydrogen bond behave differently from systems that interact only through dispersion forces. The deviations from classical behavior often are sufficiently large that conventional equations of state and activity models cannot be used without the introduction of large, condition‐dependent empirical parameters. Consequently, three different classes of theories have been developed specifically to treat hydrogen‐bonding systems. The first is based on the assumption that when molecules hydrogen‐bond, they react to form new species and consequently is referred to as “chemical” theory. The second is based on lattice‐fluid theory that is used to describe different types of specific interactions and is known as “quasi‐chemical” theory. The last is based on the solution of integral equations using a potential function that mimics that of a hydrogen bond. It is shown here that these three approaches give essentially equivalent results. This allows one to relate the parameters in the perturbation theory to the equilibrium constant and hence greatly improves its utility for real systems. All three theories are compared with simulation data.