Thermodynamic affinity in constrained free-energy systems

Pertti Koukkari, Risto Pajarre, Petteri Kangas

    Research output: Contribution to journalArticleScientificpeer-review

    2 Citations (Scopus)
    55 Downloads (Pure)


    Affinity is the generic measure of the deviation of a state from stable equilibrium. Affinity, as introduced by de Donder, is a thermodynamic state property defined in terms of p, T, and system composition during the course of a chemical change. When incorporating reaction kinetic constraints to minimization of Gibbs energy of a multiphase system, affinity can be followed in terms of the extents of the constrained reactions. This property then becomes calculated in terms of the constraint potentials received as additional Lagrange multipliers in the minimization routine. Thus, received affinities are consistent with the respective values calculated from the chemical potentials of the reactants and products of the constrained reactions and their limiting behaviour corresponds to that defined for both stationary and stable equilibrium states. The intermediate affinities can be used in the respective reaction rate calculations, or as input parameters, to define the local chemical equilibrium set by known reaction kinetic constraints. Thus, they become a useful concept in modelling reactive processes.
    Original languageEnglish
    Pages (from-to)381–394
    JournalMonatshefte für Chemie
    Issue number2
    Early online date2017
    Publication statusPublished - 2018
    MoE publication typeA1 Journal article-refereed


    This work was supported by the Strategic Research Council at the Academy of Finland, project Closeloop (Grant Number 303543).


    • CFE
    • Computational chemistry
    • Local thermodynamic equilibrium
    • Thermodynamics


    Dive into the research topics of 'Thermodynamic affinity in constrained free-energy systems'. Together they form a unique fingerprint.

    Cite this