Influence of oxidizing conditions on the condensation of aluminum oxide nanoparticles: Insights from atomistic modeling

The condensation of aluminum and aluminum oxide nanoclusters in a cooling gas of the two elements were computationally investigated at the atomistic level of details using molecular dynamics simulations based on a reactive many-body potential. The formation kinetics for particles containing up to several thousands atoms and their final morphology were scrutinized, in comparison with the oxidation of preformed aluminum nanodroplets at the same composition. In both cases the amount of oxygen in the system is found to directly control the shape, crystalline character and extent of chemical ordering, the finally obtained nanoparticles showing homogeneous or core-shell character depending on composition. Particle growth is limited under the conditions of high oxygen content. The generic role of oxidation is found to be non trivial but in satisfactory agreement with recent experimental X-ray scattering measurements of particles formed in a laser ablation plume notably probing the surface ruggedness. The ability of the simulations to unravel nanostructure morphologies at or away from equilibrium is discussed.