Mechanism and kinetics of phase transitions and other reactions in solids

TL;DR

This paper proposes a universal contact molecular mechanism for phase transitions in solids, emphasizing nucleation and interface propagation, and reveals their unique roles and characteristics in solid-state reactions.

Contribution

It introduces a unified contact mechanism for solid reactions, detailing nucleation and interface propagation, and extends the understanding to ferromagnetic transitions involving structural changes.

Findings

Nucleation is pre-coded, not fluctuation-driven.

Interface propagates by molecular filling of thin layers.

Kinetics are inherently unstable and irreproducible.

Abstract

The work is presented, leading to the universal contact molecular mechanism of phase transitions and other reactions in solid state. The two components of the mechanism - nucleation and interface propagation - are investigated in detail and their role in the kinetics is specified. They were shown to be peculiar: nucleation is "pre-coded", rather than resulted from a successful fluctuation, and the interface propagates by molecular filling of thin layers in the transverse direction. The structure of the nucleation sites is determined. The inherent instability and irreproducibility of the kinetics in question is revealed. A linear kinetics, as opposed to the bulk kinetics, is introduced and shown to be in accord with the contact mechanism. Ferromagnetic phase transition and magnetization are added to the list of solid-state reactions; neither occurs without structural rearrangement.