Scale Invariant Fractal and Slow Dynamics in Nucleation and Growth Processes

TL;DR

This paper introduces a stochastic model for nucleation and growth processes that reveals scale-invariant fractal structures and power-law decay behaviors, contrasting with exponential decay under certain conditions.

Contribution

It proposes a novel stochastic extension of the KJMA model that captures fractal and slow dynamics in nucleation and growth phenomena.

Findings

Power-law decay of metastable phase with fractal structures

Fractal dimension relates to decay exponent

Exponential decay occurs under constant or inverse time velocity

Abstract

We propose a stochastic counterpart of the classical Kolmogorov-Johnson-Mehl-Avrami (KJMA) model to describe the nucleation-and-growth phenomena of a stable phase (S-phase). We report that for growth velocity of S-phase $v=s(t)/t$ where $s(t)$ is the mean value of the interval size $x$ of metastable phase (M-phase) and for $v=x/\tau(x)$ where $\tau(x)$ is the mean nucleation time, the system exhibits a power law decay of M-phase. We also find that the resulting structure exhibits self-similarity and can be best described as a fractal. Interestingly, the fractal dimension $d_f$ helps generalising the exponent $(1+d_f)$ of the power-law decay. However, when either $v=v_0$ (constant) or $v=\sigma/t$ ($\sigma$ is a constant) the decay is exponential and it is accompanied by the violation of scaling.