László Botár

Effect of exchange reactions on transport processes: A comparison of thermodynamic treatment with random walk on lattice points

The effect of an AX+A ⇄ A+AX exchange reaction on the transport of X is discussed for a general transport process driven by the gradient in the chemical potential of AX, as well as its special cases of isothermal diffusion and electric conductivity. This treatment based on macrodifferentials is compared with a stochastic treatment of random walk on regular lattice points in one‐, two‐ , and three‐dimensional cases. The basic equivalence is proved for the two methods which ensures the application of the latter, more simple, procedure with general validity. It is also shown that the stochastic treatment reveals some aspects that remain hidden in the thermodynamic approach.

Effect of exchange reaction on transport processes: Fick's second law for diffusion on lattice points

Abstract The mass balance equation is derived for the lattice gas model of transfer diffusion in which the displacement of the centers of mass of particles is brought about by both common, “migrational”, motion and chemical exchange reaction of the type A + AX ⇌ AX + A. The form of Ficks second law involves a concentration-dependent diffusion coefficient. This concentration dependence must be taken into account when the c ( x , t ) functions are calculated by integrating the second law.

A possible construction of a complex chemical reaction network

A procedure is suggested for the construction of chemical reaction networks. We define the kinetic communication as a transfer of atoms or atomic groups between two species and determine all the kinetic communications occurring in the possible mechanism of a complex chemical process. The set of kinetic communications is the basis of the communication matrices resulting in the complete network of the overall reaction.Limiting the consideration for certain types of kinetic communications we obtain the reaction subnetworks and selecting arbitrarily species among those participating in the possible mechanism we introduced the concept of the partial subnetworks which correspond to subsets of the complete network.By the simple analysis of the subnetworks it is easy to obtain the sequence network indicating the pathways via which the selected species are formed in the course of the overall process, by the transfer of chosen atoms or atomic groups.

A Monte Carlo simulation of diffusion-controlled reactions in inhomogeneous systems

Abstract A random-walk model has been developed to treat the kinetics of reactions taking place in spurs at different solute concentrations. The dependence of the molecular yields on solute concentration has been studied using Monte Carlo techniques for simulation of the formation of spurs and of the random movement of the reactive species.

On the general and special form of Fick's second law with concentration-dependent diffusion coefficients

Abstract The migrational and reaction-driven diffusion of two components is treated as a random walk on a simple cubic lattice. It is shown that in this model the cross-terms in Ficks second law vanish even if the gradients of the concentrations are not zero.