Nucleation kinetics in phase transformations with spatially correlated nuclei

Abstract

Phase transitions ruled by nucleation and growth can occur by nonrandom arrangement of nuclei. This is verified, for instance, in thin film growth at solid surfaces by vapor condensation or by electrodeposition where, around each nucleus, a depletion zone of reactants sets up within which nucleation is prevented. In this contribution, a theoretical approach for the kinetics of phase transition with spatially correlated nuclei by progressive nucleation is developed. The work focuses on the rate of formation of the actual nuclei, a quantity that is necessary for describing the transformation kinetics. The approach is based on correlation functions and applied to treat hard-sphere interaction between nuclei. Computations have been performed for 2D and 3D growths by truncation of the series expansion in correlation functions up to second order terms. It is shown that the nucleation kinetics undergoes a transition from a typical Random Sequential Adsorption (RSA) behavior to one that is like the Kolmogorov-Johnson-Mehl-Avrami (KJMA) kinetics. The time evolution of the volume fraction of the new phase is found to depend slightly on correlation radius. Such behavior is explained by the partial balancing between the reduction in nucleation density and the decrease in impingement events, which have opposite effects on the kinetics.