Editing Le Chatelier's principle (section)

===Non-equilibrium processes===
A simple body or a complex thermodynamic system can also be in a stationary state with non-zero rates of flow and chemical reaction; sometimes the word "equilibrium" is used in reference to such a state, though by definition it is not a thermodynamic equilibrium state. Sometimes, it is proposed to consider Le Chatelier's principle for such states. For this exercise, rates of flow and of chemical reaction must be considered. Such rates are not supplied by equilibrium thermodynamics. For such states, there are no simple statements that echo Le Chatelier's principle. Prigogine and Defay demonstrate that such a scenario may exhibit moderation, or may exhibit a measured amount of anti-moderation, though not a run-away anti-moderation that goes to completion. The example analysed by Prigogine and Defay is the [[Haber process]].<ref>Prigogine, I., Defay, R. (1950/1954), pp. 268–269.</ref>

This situation is clarified by considering [[response reactions|two basic methods of analysis of a process]]. One is the classical approach of [[Josiah Willard Gibbs|Gibbs]], the other uses the near- or local equilibrium approach of [[Théophile de Donder|De Donder]].<ref>Fishtik, I.; Nagypál, I.; Gutman, (1995). ''I. J. Chem. Soc. Faraday Trans.'' '''91''':259–267. [http://www.rsc.org/Publishing/Journals/FT/article.asp?doi=FT9959100259]
</ref> The Gibbs approach requires thermodynamic equilibrium. The Gibbs approach is reliable within its proper scope, thermodynamic equilibrium, though of course it does not cover non-equilibrium scenarios. The De Donder approach can cover equilibrium scenarios, but also covers non-equilibrium scenarios in which there is only [[Thermodynamic equilibrium#local and global equilibrium|local thermodynamic equilibrium]], and not thermodynamic equilibrium proper. The De Donder approach allows state variables called [[Extent of reaction|extents of reaction]] to be independent variables, though in the Gibbs approach, such variables are not independent. Thermodynamic non-equilibrium scenarios can contradict an over-general statement of Le Chatelier's Principle.