Investigating the Crystallization Kinetics Via Time‐Resolved Neutron Diffraction

We present the use of time‐resolved neutron diffraction to investigate the crystallization kinetics at high temperature and high pressure with a time resolution of a few minutes. To highlight the potential of this approach, we present a study on the isothermal crystallization of the GeO2 in the deep supercooled liquid region at 1100 K, well below the melting temperature Tm = 1388 K. The analysis of the diffraction patterns acquired over about 67 h shows a continuous reorganization of the amorphous structure towards the α‐quartz phase. The relative fractions of crystal and amorphous material obtained from the experimental data provide a perfect test bench to develop and improve precise models for the crystallization kinetics in different thermodynamic conditions. In particular, we developed an empirical model based on a predator–prey‐like mechanism between the crystal and the surrounding amorphous medium, where the density variation controls the process. The approach presented naturally can be extended towards more complex crystallizing fluids like volcanic magmas. These are silicate melts with crystals and volatiles and the interplay between phases is pivotal in understanding and predicting their rheological properties and thus macroscopic flow and eruptive behavior.