Look at the early stages of nucleation
In classical nucleation theory, a metastable disturbed dense liquid or amorphous solid group transforms spontaneously and irreversibly into a crystalline nucleus. Jeon et al. observed the formation of gold crystals on a graphene substrate by the reduction of a precursor by means of an electron beam. Instead of the classical view, they observed a nuclear formation orbit involving dynamic and reversible fluctuations of evolving nuclei between disordered and crystalline conditions. The life in the disordered state decreases with increasing cluster size, and at sufficiently small sizes the bond energy per atom is large enough in proportion to the energy required to cause melt, that the heat given at bonding is sufficient to ‘ cause a partial collapse of an orderly group. in the disordered state.
Science, this issue p. 498
Abstract
Nuclear power in atomic crystallization remains poorly understood, despite advances in classical nuclear formation theory. The nucleation process has been described as a non-classical mechanism that includes a spontaneous transition from disordered to crystalline conditions, but a detailed understanding of dynamics requires further investigation. In situ electron microscopy of heterogeneous nucleation of individual gold nanocrystals with millisecond temporary resolution shows that the early stage of atomic crystallization is due to dynamic structural fluctuations between disordered and crystalline states, rather than by a single irreversible transition. Our experimental and theoretical analyzes support the idea that structural fluctuations are due to the size-dependent thermodynamic stability of the two states in atomic groups. These findings, based on dynamics in a true atomic system, form a new form and improve our understanding of nuclear formation mechanisms in atomic crystallization.