Ostwald rule vs. classical nucleation theory

Julien Lam, David Amans, Christophe Dujardin and Gilles Ledoux  (team Luminescence), in collaboration with Abdul-Rahman Allouche (team Physicochimie Théorique), have published an article entitled "Atomistic mechanisms for the nucleation of aluminum oxide nanoparticles" in The Journal of Physical Chemistry A.

A predictive model for nanoparticle nucleation has not yet been successfully achieved. Classical nucleation theory fails because the atomistic nature of the seed has to be considered. Indeed, geometrical structure as well as stoichiometry do not always match the bulk values. We present a fully microscopic approach based on a first-principle study of aluminum oxide clusters. We calculated stable structures of AlxOy and their associated thermodynamic properties. From these data, the chemical composition of a gas composed of aluminum and oxygen atoms can be calculated as a function of temperature, pressure, and aluminum to oxygen ratio. We demonstrate the accuracy of this approach in reproducing experimental results obtained with time-resolved spectroscopy of a laser induced plasma from an Al2O3 target. We thus extended the calculation to lower temperatures, i.e., longer time scales, to propose a scenario of composition gas evolution leading to the first alumina seeds.


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