| Ice formation, the crystallisation of igneous rock, and metallurgical and vitroceramic processes are a few examples which illustrate the importance of the crystallisation of liquids in natural and industrial processes. On a microscopic scale, however, the structural rearrangements that characterise the initial stages of the crystallisation of an amorphous material are not well understood. This leaves tremendous scope to improve the control and the understanding of crystallisation, particularly at high degrees of supercooling, where the transformation is highly irreversible. This is the context in which we decided to study medium-range changes of order occurring in a fused silicate starting to crystallise in the presence of a nucleating agent... |