Kinetics of segregation processes in solutions: Saddle point versus ridge crossing of the thermodynamic potential barrier

• Evolution of the cluster ensemble in nucleation and growth processes is studied.
• Classical Gibbs's method is compared with the generalized Gibbs's approach.
• Significant deviations from the saddle point trajectory of evolution are found.
• Scenario of nucleation is dependent on the supersaturation and surface energy.

Based on the solution of a set of kinetic equations describing nucleation and growth in solutions, the most probable path of evolution of the cluster ensemble in nucleation and growth processes is specified as a function of the initial supersaturation. The classical Gibbs' approach is employed for the description of the thermodynamic properties of the system (utilizing the capillarity approximation). As an alternative, the classical method is replaced by the generalized Gibbs' approach. It is shown that signification deviations from the saddle point of the trajectory of cluster evolution are found only if the generalized Gibbs' approach is employed, allowing one to account for and to determine the changes of the cluster state as a function of supersaturation and cluster size. In addition, the origin for the deviation of the most probable path of evolution (from the path via the saddle point of the thermodynamic potential surface) is specified.