The Coordinate Reaction Model: An Obstacle to Interpreting the Emergence of Chemical Complexity

Abstract

The way chemical transformations are described by models based on microscopic reversibility does not take into account the irreversibility of natural processes, and therefore, in complex chemical networks working in open systems, misunderstandings may arise about the origin and causes of the stability of non‐equilibrium stationary states, and general constraints on evolution in systems that are far from equilibrium. In order to be correctly simulated and understood, the chemical behavior of complex systems requires time‐dependent models, otherwise the irreversibility of natural phenomena is overlooked. Micro reversible models based on the reaction‐coordinate model are time invariant and are therefore unable to explain the evolution of open dissipative systems. The important points necessary for improving the modeling and simulations of complex chemical systems are: a) understanding the physical potential related to the entropy production rate, which is in general an inexact differential of a state function, and b) the interpretation and application of the so‐called general evolution criterion (GEC), which is the general thermodynamic constraint for the evolution of dissipative chemical systems.

Physical Chemistry Models for Chemical Research in the XXth and XXIst Centuries

“…Note that the use of activities instead of concentrations does not change the points discussed here concerning the irreversible thermodynamic scenario. We emphasize that σ e is an important aspect of open-flow reactors, essential for achieving entropy balance in nonequilibrium stationary states (NESS). ,, The sum (σ + σ e ) gives the entropy balance eq per unit volume, V − 1 × d S d t , and the inequality presented below in Scheme (see section ) shows how the temporal behavior of entropy production and exchange is conditioned by the changes in the chemical affinities of the reactions and the pseudoreactions in the nonlinear regime of nonequilibrium thermodynamics.…”

“…We emphasize that σ e is an important aspect of open-flow reactors, essential for achieving entropy balance in nonequilibrium stationary states (NESS). 8,30,66 The sum (σ + σ e ) gives the entropy balance eq 9 per unit volume, V S t…”

“…for complex chemical systems, the NESS of the thermodynamic branch may become unstable, and this conceptual continuum extension between irreversible and equilibrium thermodynamics is broken. In this new scenario, 8 the system may evolve to a new stable NESS, but also to oscillatory states, and even to full chaotic behavior. This theoretical description belongs to the topic of energy dissipative systems.…”